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Updated: 4 weeks 10 hours ago

New studies confirm weakening of the Gulf Stream circulation (AMOC)

Thu, 09/17/2020 - 15:55

Many of the earlier predictions of climate research have now become reality. The world is getting warmer, sea levels are rising faster and faster, and more frequent heat waves, extreme rainfall, devastating wildfires and more severe tropical storms are affecting many millions of people. Now there is growing evidence that another climate forecast is already coming true: the Gulf Stream system in the Atlantic is apparently weakening, with consequences for Europe too.

The gigantic overturning circulation of the Atlantic water (dubbed AMOC) moves almost 20 million cubic meters of water per second – almost a hundred times the Amazon flow. Warm surface water flows to the north and returns to the south as a cold deep current. This means an enormous heat transport – more than a million gigawatts, almost one hundred times the energy consumption of mankind. This heat is released into the air in the northern Atlantic and has a lasting effect on our climate.

But since the 1980s, climate researchers have been warning of a weakening or even a cessation of this flow as a result of global warming. In 1987, the famous US oceanographer Wally Broecker titled an article in the scientific journal Nature “Unpleasant surprises in the greenhouse”. Even Hollywood took up the subject in 2004 in the film “The Day After Tomorrow” by the German director Roland Emmerich. However, there were no measurement data that could prove an ongoing slowdown.

Only since 2004 has there been continuous monitoring at 26°N in the Atlantic (RAPID project). Although the data show a weakening of the current system, the measurement series is still too short to distinguish a possible climate trend from decadal variability. For the longer-term development of the Gulf Stream system, we must therefore rely on indirect evidence.

A long-term AMOC weakening should lead to a cooling in the northern Atlantic. Such a regional cooling in the middle of global warming has been predicted by climate models for a long time. And indeed, the evaluation of data on sea surface temperatures shows that the northern Atlantic is the only region of the world that has escaped global warming and has even cooled down since the 19th century (see graph). In addition, one can see a particularly strong warming off the North American coast, which according to model simulations is part of the characteristic “fingerprint” of a weakening of the Gulf Stream circulation.

Diagram of the Gulf Stream system with the warm surface current and the cold deep current. The actual Gulf Stream off the US coast is a part of this more comprehensive circulation system. The color shading shows the measured temperature trend since the late 19th century. This diagram is based on Caesar et al., Nature 2018 and first appeared in the Washington Post.

This fingerprint is regarded as important evidence, and not least because of this, the Intergovernmental Panel on Climate Change (IPCC) stated for the first time a year ago in the Summary for Policy Makers of its Special Report on the Oceans:

 “Observations, both in situ (2004–2017) and based on sea surface temperature reconstructions, indicate that the Atlantic Meridional Overturning Circulation (AMOC) has weakened relative to 1850–1900.”

New studies support long-term weakening

Two new studies now provide further independent evidence of this weakening. In August a paper by Christopher Piecuch of the Woods Hole Oceanographic Institution on the Florida Current – the part of the Gulf Stream system along the Florida coast – was published. Although continuous measurements of the current have only been available since 1982, Piecuch was able to reconstruct the strength of the Florida Current over the last 110 years from measurements of the sea level difference between the two sides of the current. To do so, he used 46 tide gauge stations in Florida and the Caribbean as well as a simple physical principle: the Coriolis force deflects currents in the northern hemisphere to the right, so that the water on the right side of a current stands higher than on the left. The stronger the current, the greater the difference in sea level. Comparison with measurements since 1982 shows that the method works reliably.

The result: the Florida current has weakened significantly since 1909 and in the last twenty years has probably been as weak as never before. Piecuch’s calculations also show that the resulting reduction of heat transport is sufficient to explain the ‘cold blob’ in the northern Atlantic.

This Monday, in Nature Climate Change a further study appeared, of researchers of Peking University and Ohio State University (Chenyu Zhu and Zhengyu Liu). For the first time, their paper provides evidence for an AMOC slowdown based on data from outside the North Atlantic. Model simulations show that a weakening of the AMOC leads to an accumulation of salt in the subtropical South Atlantic. This is due to the fact that strong evaporation in this region constantly increases the salinity, while the upper branch of the ocean circulation drains the salty water northwards, continually bringing in less salty water from the south. When this current weakens, the water in this region becomes saltier. This is exactly what the measured data show, in accordance with computer simulations. The authors speak of a “salinity fingerprint” of the weakening Atlantic circulation.

Video animation of ocean currents in the CM2.6 climate model of the Geophysical Fluid Dynamics Lab in Princeton:

In addition to these oceanographic measurements, a number of studies with sediment data indicate that the Gulf Stream circulation is now weaker than it has been for at least a millennium.

These current changes also affect Europe, because the ‘cold blob’ out in the Atlantic also influences the weather. It sounds paradoxical when you think of the shock frost scenario of the Hollywood blockbuster The Day After Tomorrow: but British researchers found that in summer the jet stream in the atmosphere likes to take a route around the south side of the cold blob – this then brings warm winds from the southwest into Europe, leading to heat waves there, as in the summer of 2015. Another study found a decrease in summer precipitation in northern Europe and stronger winter storms. What exactly the further consequences will be is the subject of current research.

However, the latest generation (CMIP6) of climate models shows one thing: if we continue to heat up our planet, the AMOC will weaken further – by 34 to 45% by 2100. This could bring us dangerously close to the tipping point at which the flow becomes unstable.

This article appeared originally in German in Der Spiegel: Das Golfstromsystem macht schlapp

Categories: Blogtastic

Unforced variations: Sep 2020

Tue, 09/01/2020 - 21:33

This month’s open thread on climate science topics. Things to look for – Arctic sea ice minimum, boreal wildfires and the Atlantic hurricane season – you know, the usual…

Categories: Blogtastic

Denial and Alarmism in the Near-Term Extinction and Collapse Debate

Fri, 08/21/2020 - 01:18

Guest article by Alastair McIntosh,  honorary professor in the College of Social Sciences at the University of Glasgow in Scotland. This is an excerpt from his new book, Riders on the Storm: The Climate Crisis and the Survival of Being

Mostly, we only know what we think we know about climate science because of the climate science. I have had many run-ins with denialists, contrarians or climate change dismissives as they are variously called. Over the past two years especially, concern has also moved to the other end of the spectrum, to alarmism. Both ends, while the latter has been more thinly tapered, can represent forms of denial. In this abridged adaptation I will start with denialism, but round on the more recent friendly fire on science that has emerged in alarmism.

Climate change dismissives

One of my more peculiar run-ins with a dismissive voice was through an online debate in 2010 that ECOS, the journal of the British Association of Nature Conservationists, organised between me and an English wildlife ecologist, Peter Taylor. Taylor’s 2009 book, Chill, argued that far from living in a world that’s heating up, ‘the period 2002–07 marks a turning point, then glaciers will begin to grow and ice mass begin to accumulate again, thus levelling off the sea level rises’. He saw the cold winter of 2008–9 as heralding the coming ice age(1). Being an ecologist, this made him a hero of climate change denialism, an avid convert from the other church; and for a time, Chill ranked as number one in Amazon UK’s bestselling league for ‘global warming’.

Invariably I have found myself asking of such figures, who have no credibly peer-reviewed publications in climate science: what makes them think that they know better than experts with a reputation worth not losing? I also ask myself what drives their attitudes. Often, these are a class of people heavily invested in consumerist lifestyles. Their material markers of identity and prestige, and their masks of distraction from what is challenging in life may be at stake. Some just don’t care. I define consumerism as consumption that is in excess of what is needed for a dignified sufficiency of living. However, a handful of the most effective dismissives don’t fit obvious characterisation, being more altruistic in holding their position. Peter Taylor is one such, and my late friend the botanist and TV celebrity Professor David Bellamy was another. Taylor concedes that the heavy impact of climate mitigation measures on nature and landscapes – terrestrial wind farms in particular – has influenced his views. Bellamy, likewise.

At the time of our ECOS exchange, Taylor praised it, saying: ‘I know of no other consistent debate on this important issue.’ Not having been in touch for years, I dropped him a line while writing this book. I asked: given that his forecast ‘chill’ has not materialised, did he think that it was coming yet, for all that? His reply was characteristically warm and cheerful. It left my question feeling almost mean-spirited. He made no reference back to his previous predictions. Instead, to my astonishment, he wrote of ‘record warmth – just as we could expect’, that the current warm period ‘may have two or three centuries to run’, and the next ice age is not just around the corner but ‘three to four hundred years away’(2). It seemed that the denial had full astern gone retrograde. I scratched my head and gave a weary nod to all those hours spent on the ECOS great debate.

Heavy ad hominem artillery

Other run-ins have had a less avuncular if, paradoxically, a more jaunty feel to them. The Global Warming Policy Foundation (GWPF) is Britain’s foremost ‘climate sceptic’ lobby group. Set up by Lord (Nigel) Lawson of Blaby, Mrs Thatcher’s former chancellor of the exchequer, its website is literally a ‘dark’ web in its presenting colour scheme. Its board comprises a formidable array of heavyweight political figures, contrarian scientists and erstwhile captains of commerce, the media and the civil service. To see power at work – elevated, concentrated and networked – go no further than to take a look online, and gape(3). Most such lobby bodies no longer say that global warming isn’t happening. Instead, they’ll take issue with abstruse elements of the scientific data, with the extrapolated rate of heating, with the attribution of its causes or with the expected impact and anticipated costs – not least the ‘socialist’ taxation and regulatory implications – of actually doing something.

Lord Lawson refuses to disclose the sources of the GWPF’s funding, conceding only that he relies on friends who ‘tend to be richer than the average person and much more intelligent than the average person’(4). Since 2017 its deputy-director has been Andrew Montford, a chemist by original training, turned chartered accountant(5). My encounter with Montford came in 2010 when The Scottish Review of Books asked me to review his investigative work, The Hockey Stick Illusion: Climategate and the Corruption of Science, which claims to be a ‘demolition of the veracity’ of Michael Mann’s hockey stick curve(6). Like Taylor’s Chill a year earlier, the book quickly achieved cult status amongst climate change deniers. I concluded that at best it might help to keep already-overstretched scientists on their toes. At worst, it was a yapping terrier worrying the bull, one that cripples action, potentially costing lives and livelihoods(7).

Montford runs a blog from which, under the pseudonym of ‘Bishop Hill’, he lampoons the high priests (as he sees them) of climate science and all such hooey as green taxes, subsidies, legislation and self-righteous preaching from the likes of, well, yours faithfully. His Grace, as his congregation deferentially refer to him, responded to my piece with two blogs that had me tossed into the dungeons of the Inquisition for heretical impertinence, an abomination unto the sensibilities of the Lord. A crusade was launched, a jihad ensued, and fusillades were fired from keyboards poised in every corner of his parish. In all, some 150 comments linger as remaining landmines on the good bishop’s website.

‘He is an enemy of the people and the state and is declared anathema,’ said one. I took the humour as a badge of office. Even better, said another: ‘Deploy heavy ad hominem artillery to characterize [him] as a coprophagic protocranial.’ Verily, it’s a sorry day when a literary reviewer has to go and look up even simple dictionary words. ‘Adopt a lordly disdain and ignore him.’ ‘He and his eco-chums are in it for the money.’ ‘Another one of these weird Highlanders who seem to dominate Scotland.’ ‘Alastair, just keep tossing off your caber.’ ‘Yer Grace, show no quarter, none will be given.’ ‘He deserves a kicking.’(8)

I came out of such a Punch and Judy show well able to brush off the laugh. But it was all right for me. I make use of climate science coming from an early background of just a general earth sciences degree. I pitch no claim to be a climate scientist. Others, at the heart of science – whether Mann in the USA, or the English scientists such as Phil Jones caught up at the heart of ‘Climategate’ at the University of East Anglia – suffer for their work. No quarter is the order of their day.

Alarmism, doomism and Roger Hallam

What most scientists had not foreseen with an eye so fixated on the artillery of denialism, was the sustained and one would presume well-intentioned misuse of science from the other end of the spectrum, by those who do accept the reality of climate change. When Extinction Rebellion began in England, it conveyed a sense of being witnesses to the cascade of plant and animal extinctions that are escalating around the world as many habitats become less habitable. There is no scientific quibble with that. However, the narrative soon escalated to human death on a massive and imminent scale. As the prominent co-founder Roger Hallam saw it, the burning question had become: ‘How do we avoid extinction?’

His 2019 manifesto, Common Sense for the 21st Century(9), was written in his own name but widely hailed as representing the views of Extinction Rebellion and heavily promoted by the organisation’s London HQ. Referencing his claim to ‘one recent scientific opinion’, he warns of 6 to 7 billion people dead as a result of climate change ‘within the next generation or two’. The paper cited as his authority in the footnotes makes no such claim(10). It is purely Hallam’s extrapolation of a 5°C world, given what Common Sense calls ‘the central role of methane in a climate emergency . . . with the system spiralling out of our control and the likelihood of global collapse within a decade or two’. He reiterated the mass dieback claim in a BBC News interview feature, trenchantly insisting: ‘I am talking about the slaughter, death and starvation of 6 billion people this century – that’s what the science predicts.’(11)

Climate Feedback, a website more used to taking on deniers than alarmists, invited an expert panel to give their opinions on this prediction. The responses ranged from ‘an illustration of a worst-case scenario’ to ‘wild speculation’. Ken Caldeira, senior scientist at the Carnegie Institution, put it bluntly: ‘I know of no climate model simulation or analysis in the quality peer-reviewed literature that provides any indication’ that there is a substantial probability, above zero, of 6 billion deaths this century.(12)

Jem Bendell and ‘Deep Adaptation’

Meanwhile, a variation of the theme was coming in from Jem Bendell, a business school professor at the University of Cumbria in the north of England. An expert in digital currencies, his staff web page playfully describes how it earned him the moniker ‘Professor Bitcoin’(13). Bendell’s contribution to Extinction Rebellion’s manifesto, This is Not a Drill, tells that he ‘grieved how I may not grow old’(14). The manifesto thesis for which he is now known, Deep Adaptation, anticipates ‘inevitable near-term social collapse due to climate change’ resulting in ‘probable catastrophe and possible extinction’(15). This, as he wrote on his blog, could be expected ‘in many, perhaps most, countries of the world . . . within 10 years’(16). He spelt out both the imminence and what it would look like in a roundup of where he considered the climate science stood as of 2018.

‘But when I say starvation, destruction, migration, disease and war, I mean in your own life. With the power down, soon you wouldn’t have water coming out of your tap. You will depend on your neighbours for food and some warmth. You will become malnourished. You won’t know whether to stay or go. You will fear being violently killed before starving to death.’(17)

Deep Adaptation was originally an academic paper that had failed peer review for lack of scholarly rigour. Bendell posted it to the web in 2018, achieving an astonishing half a million downloads within the first year. Part of his rationale leans on what he describes as ‘data published by scientists from the Arctic News’. However, Arctic News is no scholarly tome. It is a blog site that, amidst lurid illustrations, invokes the methane bomb and projects a possible global temperature rise of 10°C, by 2026, based on ‘adjusted NASA data’ heralding the ‘mass extinction of man’(18). Again, the pushback comes from within the scientific community itself. A journalist asked Gavin Schmidt, the director of NASA’s Goddard Institute for Space Studies and one of the world’s leading climate experts what he made of Bendell’s paper. Schmidt said, and further pressed the point on his Twitter account, that it mixes ‘both valid points and unjustified statements throughout’, but is ‘not based on anything real’(19).

In a 2019 blog, Bendell responded to criticisms of his slant on the science. He describes his grief at having chosen not to have children, partly because they are ‘the greatest contribution to carbon emissions that you could make’ and partly out of ‘the realization of the world they will have to live and die within’. He concludes that in future he will not be replying to, but rather, stepping away from, such controversies around his scientific claims to focus instead on building up the community around Deep Adaptation(20), the activities of which include workshops, trainings, residencies in Bali, and an annual retreat at a yoga centre in Greece to ‘support peaceful empowered surrender to our predicament, where action can arise from an engaged love of humanity and nature, rather than redundant stories of worth and purpose’(21).

However, within a year of his withdrawal from scientific debate, he wrote a further blog having requested Schmidt to render his criticism specific. Schmidt obliged, providing a raft of reproofs including his assessment that Deep Adaptation’s take on Arctic methane was ‘totally misleading’, and that its pitch on runaway climate change was ‘nonsense’. The professor, whose day job was to teach ‘a sustainability-themed MBA programme’, was unwilling to concede any significant ground to NASA’s top climate scientist. Digging in his heels, the blog concluded: ‘I have identified two minor corrections and two clarifications I will make on the paper. However, none of those are material to the situation we are in and none of the main points are revoked.’(22)

Shortly afterwards, BBC News ran a feature that profiled Bendell and his most ardent ‘followers’ as ‘climate doomers’. It quoted Myles Allen, professor of geosystem science at the University of Oxford, as saying that he considers Deep Adaptation to display ‘the level of science of the anti-vax campaign’(23). In counterpoint, it also cited Will Steffen, a retired scientist who had served on the Australian Climate Commission, suggesting that Bendell may be ‘ahead of the game in warning us about what we might need to prepare for’. The pity of it all is that Bendell’s core agenda – about the need for resilience, relinquishment, restoration, and recently he has added reconciliation – is both necessary and inspiring. That is why he has gathered such a following amongst people who are hungry for deeper meaning. We need people like him and Hallam who, at their most effective, and if they discipline themselves to the settled science, can take an overview of things, drawing out what most matters, contextualising it and presenting it to the public in ways more digestible than the raw IPCC reports. There is for each of us so much that is good and right to do anyway, without having to overreach our fields of expertise, conflate climate change with other causes and play fast and loose with signs seen in the sky.

Arctic News, McPherson and doomsday 2026

Meanwhile, Arctic News’ chosen doomsday date of 2026 doubles as the apocalyptic year of choice of Guy McPherson, a retired professor of evolutionary and resource ecology at the University of Arizona, and Bendell’s referenced source in Deep Adaptation where discussing fears of an ‘inevitable methane release . . . leading to the extinction of the human race’(24). McPherson, in turn and in a way that starts to feel rather circular, references his claims back to material from Arctic News, as well as to extrapolation from a range of scientific papers and other sources that, he says, ‘even 10-year-olds understand . . . and [that] Wikipedia accepts [as] the evidence for near-term human extinction’. The phrase used there, Near Term Human Extinction, has gathered a considerable ecopopulist cult following, complete with the social media hashtag #NTHE and online mental health support groups for the depressed and suicidal. The professor crisply reiterated and summed up his position in an interview given in 2018: ‘Specifically, I predict that there will be no humans on Earth by 2026, based on projections of near-term planetary temperature rise and the demise of myriad species that support our own existence.’(25)

His website, Nature Bats Last, prominently offers suicide advice on its home page [Ed. which we are not linking to]. While advising against such a move, he counsels that it can nevertheless ‘be a thoughtful decision’, and with this endorsement he bizarrely links to the post-mortem website of Martin Manley of Kansas, who intricately blogged the preparations for his own departure by self-inflicted gunshot in a parking lot(26). For those who believe in the severity and particularly the imminence of their prognostications, such alarmism arguably crosses over into the realm of fantasy. If conflated with reality, this risks its own potentially tragic consequences.

Breakdown to break through?

There are other sides to the position that I have taken here against alarmism. An activist friend put it to me that what Bendell’s work does is that it pushes a point to make a point. It usefully brings people to the state of breakdown, from where they can break through into the new social norms that are demanded by deep adaptation. It also expresses the precautionary principle. My view, is that if a case can’t be made without it being over-egged, either the case is not valid or those to whom it is being pitched are being spun. Exaggeration or invoking fear and panic only entrenches positions and sets up a backlash. The unembellished science is quite bad enough to be good enough.

I get people coming up at my talks, or sending in an email, then being disappointed when I tell them that I only partly buy into the fears stimulated by prominent alarmists. Because I say I’m sticking to consensus science – even knowing that it can never be bang up to date and that its expression will be sure but probably cautious – I suspect they sometimes think that I’m the denier. A climate model researcher in Sweden dropped me a line, saying that he gets the same disappointed reactions, adding that ‘some teenagers are distraught on this, so the alarmism of such actors is taking a heavy and unjustifiable psychological toll on others.’ Those who work with young people warn of the consequences of growing ‘climate anxiety’(27).

None of this is to suggest that what is happening to the planet ought not provoke anxiety. I said to the climate scientist Katharine Hayhoe, that I often find myself racked between the deniers and the alarmists, trying to hold on to the humanity of both, recognising their fears or differing priorities, and yet insisting on consensus science. She answered, ‘It is a narrow and lonely place so it’s great to have company!’(28). Michael Mann concurs. He sees ‘doomism and despair’ that exceeds the science as being ‘extremely destructive and extremely influential’. It has built up ‘a huge number of followers and it has been exploited and co-opted by the forces of denial and delay’. ‘Good scientists aren’t alarmists,’ he insists. ‘Our message may be – and in fact is – alarming . . . The distinction is so very, very critical and cannot be brushed under the rug.’(30)

Neither Hayhoe nor Mann are the kind of scientists who take distance from campaigning as ‘climate advocates’, as the former puts it. Both openly support and encourage protest that rests on a firm evidence base. In April 2019, they were amongst the twenty-two lead authors of a letter to Science, headed ‘Concerns of young protesters are justified.’ Along with more than 3,000 other experts who added their names as co-signatories, it stated: ‘We call for our colleagues across all disciplines and from the entire world to support these young climate protesters. We declare: Their concerns are justified and supported by the best available science.’

The tension, then, is not between science and protest. The tension is between science and multiplying up its extreme ends of likelihood in ways that are tantamount to pseudoscience: ‘If the worst imaginable happens it is this. And if the worst of that happens, it is this.’ The ancient Celts were justified in their greatest fear that the sky would fall in. The asteroid may be on its way right now. But real science balances up the probabilities.

Millennialism or future possibilities?

Like denialism, alarmism distorts our temporal horizons of what is possible. As the veteran Greenpeace campaigner Chris Rose suggests, its ‘gloom picking’ leads to ‘solutions denial’ that ramps up ‘climate grief’ that exploits the poorly informed(31). In their panic, many of its key proponents advocate potentially disastrous fixes, the magic bullet of geoengineering especially, and that, in the form of solar radiation modification. I agree with those who say: ‘There isn’t enough time.’ And yet, the opposite of one great truth is very often another great truth. As an Arabic proverb puts it: ‘Haste is the key to sorrow.’ If our politics are deep green, we must pay attention to the fact that, already, nativist forms of ecofascism have drawn blood on growing alt-right fringes of drawbridge environmentalism. The ‘Unabomber’ and the Christchurch mosque gunman both appealed to certain types of ‘green’ narrative in their manifestos(32).

All this is why I walk along the ridge of Katharine Hayhoe’s ‘narrow and lonely place’. To over-egg the cake is like those terrorist alerts that remain forever high. Alarmists who extrapolate beyond sound evidence may be right, but if so, by the wrong process. The upside, is that they may perversely hit it lucky and warn of something of which others had been too cautious. The downside, is that in the long run they undermine the very principles of truth that they purport to speak.

Alarmism feeds upon the natural fears and decent trust of the understandably uninformed. It allows the enemies of climate action to paint climate science as the domain of wacky prophets and their followers, who have to keep on revising upwards their forecast date of doomsday. It draws those who have been caught up in such thinking into the cognitive dissonance reduction of looking for, and in a strange way maybe even hoping, that the signs on which they have staked so much are being fulfilled. This chimera of narratorial control affords an illusory sense of agency, and perhaps prestige, to individuals who may lack the humility, or be too captivated by their personal fears, to accept the limitations of their knowing as well as the wider ambiguities of emergent knowledge. Where pronounced, such alarmism can echo a ‘conspiracy mentality’ zeal, such as the philosopher Quassim Cassam characterises in figures who might be ‘quick to denounce mainstream academia for rejecting their theories [yet] crave academic respectability … and trumpet their PhDs, whatever their subject.’(33)

Moreover, in an age of perhaps renewed spiritual searching this can pander to climate change millennialism in a ‘phony holy’ cultic psychology. Certainly, it might correctly second guess the future. But if so, probably only as an artifact of flawed or grandiose reasoning. More probably, it will merely escalate the psychological defensive mechanisms used to maintain ‘cognitive consistency’, and these, much as Festinger and colleagues memorably described in their 1950s doomsday study, When Prophecy Fails.(34)

The only remedy is that in our understandable despair and burning yearning for change, we must keep head engaged, as well as heart and hand. We have no mandate to collapse the possibilities of the future, to contract and restrict our latitude for agency and action. Climate change denial is a waste of time. But climate change alarmism is a theft of time.

  1. Peter Taylor, Chill: A reassessment of global warming theory, Clairview, East Sussex, 2009, pp. 232, 268–9, 301. The ECOS debate in 2010 has since been lost in a website revamp. I retain the email thread.
  2. Emails from Peter Taylor drawn upon here are 31 October 2010 and 18–19 November 2019.
  3. Board of Trustees’, Global Warming Policy Foundation, 3 February 2020.
  4. Bob Ward, ‘Secret funding of climate sceptics is not restricted to the US’, The Guardian, 15 February 2013.
  5. Andrew W. Montford’, Desmog, 2017.
  6. Montford, A.W., published by Stacey International, London, 2010. See also Tamino, ‘The Montford Delusion’, RealClimate, 22 July 2010.
  7. Alastair McIntosh, ‘Review of The Hockey Stick Illusion’, Scottish Review of Books, 6:3, August 2010.
  8. Bishop Hill, ‘Scottish Review of Books’, 14 August 2010; and ‘Did he read it?’ 17 August 2010.
  9. Roger Hallam, Common Sense for the 21st Century, PDF version 0.3.
  10. Xu paper used by Hallam: Yangyang Xu and Veerabhadran Ramanathan, ‘Well below 2°C: Mitigation strategies for avoiding dangerous to catastrophic climate changes’, PNAS, 114:39, 2017, pp. 10,315–23.
  11. BBC News, Roger Hallam interviewed by Stephen Sackur, BBC HardTalk, 17 August 2019.
  12. Scott Johnson (ed.), ‘Prediction by Extinction Rebellion’s Roger Hallam that climate change will kill 6 billion people by 2100 is unsupported’, Climate Feedback, 22 August 2019.
  13. University of Cumbria, ‘Professor Jem Bendell, PhD’, Institute for Leadership Sustainability, Business.
  14. Jem Bendell, ‘Doom and Bloom: Adapting to Collapse’, This is Not a Drill, op. cit., pp. 73–7.
  15. Jem Bendell, Deep Adaptation: a Map for Navigating Climate Tragedy, IFLAS Occasional Paper 2 (Postscript: The link to the original 27 July 2018 version of the paper on this landing site, the version from which I have quoted, was taken down and replaced with a Revised 2nd Edition on 27 July 2020. The original can still be accessed online. The new version came a fortnight after a challenging and much-remarked upon criticism of the science of Deep Adaptation from three scientist members of Extinction Rebellion: Thomas Nicholas, Galen Hall and Colleen Schmidt, ‘The faulty science, doomism and flawed conclusions of Deep Adaptation’, Open Democracy, 14 July 2020. Amongst the changes made, are that a section about Arctic methane has been removed, meaning that Arctic News is no longer cited within the body text although it remains in the references. Most revealing is a welcome change made in the abstract. The original opened: ‘The purpose of this conceptual paper is to provide readers with an opportunity to reassess their work and life in the face of an inevitable near term social collapse due to climate change.’ The revised, shifts from a statement of fact to one of opinion (my italics): ‘The purpose of this conceptual paper is to provide readers with an opportunity to reassess their work and life in the face of what I believe to be an inevitable near-term societal collapse due to climate change.’ Bendell has pushed back strongly against the Open Democracy critique, commencing with his riposte: ‘Letter to Deep Adaptation Advocate Volunteers about Misrepresentation of the Agenda and Movement‘, Professor Jem Bendell blog, 15 July 2020. An extensive debate followed on Twitter, for example, multiple threads down from Tom Nicholas).
  16. Jem Bendell, ‘A Year of Deep Adaptation’, Professor Jem Bendell blog, 7 July 2019. This is also the source of the half-million downloads statistic. Note that the coronavirus is not (in any obvious way) caused by climate change.
  17. Jem Bendell, ‘A Summary of Some Climate Science in 2018’, Professor Jem Bendell blog, 22 March 2018.
  18. Arctic News page linked by Bendell: Sam Carana, ‘Warning Climate Warning!! Alert: Signs of Extinction’, Arctic News, 3 March 2018. I’ve also cited from pages linked thereto. A number of the writers featured in Arctic News, including John Nissen, were associated a decade ago with AMEG, the Arctic Methane Emergency Group.
  19. Mann and Schmidt, Twitter thread, 22 November 2019. Schmidt, first quote in the tweet, second in the Nafeez Ahmed Vice article linked by Mann to whom Schmidt was responding.
  20. Jem Bendell, ‘Responding to Green Positivity Critiques of Deep Adaptation’, Resilience, 15 April 2019.
  21. Deep Adaptation Retreat with Jem Bendell and Katie Karr: Inner resilience for tending a sacred unravelling’, Kalikalos Holistic Network, 2020. Also, with comments at the bottom around the dilemmas of flying to such a location in 2018 retreat) and (2019 retreat).
  22. Jem Bendell: ‘The Worst Argument to Try to Win: Response to Criticism of the Climate Science in Deep Adaptation’, Professor Jem Bendell blog, 27 February 2020.
  23. Jack Hunter, ‘The “climate doomers” preparing for society to fall apart’, BBC News, 16 March 2020.
  24. Bendell, Deep Adaptation, op. cit., with citation to Guy McPherson’s ‘Climate Change Summary and Update’, Nature Bats Last, update 2 August 2016.
  25. Rajani Kanth, ‘On Imminent Human Extinction: [Guy McPherson] Interviewed by Rajani Kanth’, Nature Bats Last, 12 October 2018. Also, Guy McPherson, Twitter, 25 September 2019: (tweet now unavailable, account now deleted).
  26. Guy McPherson, ‘Contemplating Suicide? Please Read This’, Nature Bats Last, 8 July 2014.
  27. Matthew Taylor and Jessica Murray, ‘“Overwhelming and terrifying”: the rise of climate anxiety’, The Guardian, 10 February 2020.
  28. Katharine Hayhoe, Twitter, 19 December 2019.
  29. Michael Mann (on Guy McPherson), Twitter, 13 August 2019.
  30. Michael Mann, Twitter, 16 February 2019:
  31. Chris Rose, ‘Tragedy or Scandal? Strategies Of GT, XR and the New Climate Movement’, Three Worlds blog, 13 February 2020. Full paper.
  32. Likewise, the debate around green Nazism. See Franz-Josef Brüggemeier, Marc Cioc and Thomas Zeller (eds), How Green Were the Nazis? Nature, Environment, and Nation in the Third Reich, Ohio University Press, 2005.
  33. Quassim Cassam, Conspiracy Theories, Polity Press, Cambridge, 2019, p. 25.
  34. Leon Festinger, Henry Riecken & Stanley Schachter, When Prophecy Fails: A Social and Psychological Study of a Modern Group That Predicted the Destruction of the World, Harper, New York, 1964.

Categories: Blogtastic

How to spot “alternative scientists”.

Wed, 08/12/2020 - 05:52

Recently, a so-called “white coat summit” gave me a sense of dejavu. It was held by a group that calls itself ‘America’s Frontline Doctors’ (AFD) that consisted of about a dozen people wearing white coats to the effect of achieving an appearance of being experts on medical matters.


The AFD apparently wanted to address a “massive disinformation campaign” (what irony) and counter the medical advice from real health experts. This move has a similar counterpart in climate science, where some individuals also have claimed to be experts and dismissed well-established scientific facts, eg. that emissions of CO2 from the use of fossil fuels results in global warming.


Climate science is not the only discipline where we see confusion sown by a small number of “renegades”. A few white-coated scholars have disputed the well-established danger of tobacco. We see similar attitudes among the “Intelligent Design” community and the so-called “anti-vaxxers”.


Statistically speaking, we should not be surprised by a few contrarians who have an exceptional opinion within a large scientific community. It is to be expected from a statistical point of view where there is a range of opinions, so there should be little reason to make a big deal out it.


On the other hand, there are some fascinating stories to be told. Sometimes there are individuals who can be described as “crackpots” and “quakesalvers” (e.g. a scholar believing in dowsing rods among the climate renegades and some within the AFD who talk about demons). Hollywood has even realized that some scientists may be mad, which has given us the familiar term “mad scientist”. But all “renegades” may of course not necessarily be mad.


Nevertheless, according to Snopes, the background of the individuals of the AFD is rather colourful. And there is nothing in the background provided about them that gave me any confidence in their judgement. On the contrary.


A sign that should trigger a big warning is that Snopes found it difficult to see who the AFD really are or where their conclusions really come from. The transparency is lacking and their story is murky. Especially so if the results have not been published through renowned peer-reviewed scientific journals. This is something we have seen time and again with climate change contrarians.


Any claim would be more convincing if colleagues independently are able to replicate the work and get the same results (without finding anything wrong with the process). This would require transparency and openness.


Another sign that should make you skeptical is if the claims have a dogmatic character. The AFD address is all dogma. This is also typical among the science deniers.


It’s also typical that the extreme fringes cannot falsify the established science and therefore move on to conspiracy theories. In the case of AFD, it is the alleged “massive disinformation campaign”.


Should we take such fringe views seriously? This type of “infodemics” seems to become a growing problem as described in a feature article in Physics World July 2020: ‘Fighting flat-Earth Theory’. The term “infodemic” reflects the fact that false information is just as contagious as an epidemic. Imposters dressed in white coats peddling false information can cause harm if people take them seriously.


The damage caused by erroneous information and conspiracy theories is discussed in the HBO documentary ‘After truth’, and the wildest claims can spread like a rampant disease as shown in that film.

We have witnessed how misinformation and lack of trust of true medical sciences have caused bad situations in some countries, while in others (eg. New Zealand, Canada, and some Nordic countries) the pandemic has been kept under control because the general public in general has followed the scientific health advice.


There is a common denominator when it comes to the AFD, anti-vaxxers, flat-earthers, “intelligent design”, chem-trail evangelists and those dismissing climate science. I think it may be useful to join forces within the broader scientific community to help the general public understand the real issues. This effort should also be on more general terms. People have a right to reliable and truthful information. Everybody should understand that anyone who spreads bullshit or lies also shows you a great deal of disrespect. The same goes for platforms spreading disinformation.


So what can we do to make people understand how science works and enhance the general science literacy? Is it better to teach people how to spot these “alternative scientists” (the term is inspired by “alternative facts”), conspiracy theories, and falsehoods, if we show a range of examples from different disciplines? We can probably learn from each others. There seems to be a lesson to be learned from the pandemic.

Categories: Blogtastic

Forced Responses: Aug 2020

Sat, 08/01/2020 - 11:48

This is the bimonthly thread on climate solutions. Climate Science discussions should go here.

Categories: Blogtastic

Unforced Variations: Aug 2020

Sat, 08/01/2020 - 11:45

This month’s open thread for climate science issues. People might want to keep an eye on the Arctic sea ice

Categories: Blogtastic

Somebody read the comments…

Wed, 07/29/2020 - 03:03

This post is just to highlight an interesting paper that’s just been published that analyzed the comment threads here and at WUWT.

Out now in Science Communication! We find that users in comment sections of climate change blogs mostly deploy polarizing strategies, which ultimately do not resolve framing differences. #openaccess

— Christel van Eck (@ChristelvanEck) July 28, 2020

In it, the authors analyze how the commenters interact, argue and attempt to persuade, mostly, to be fair, unsuccessfully. It may be that seeing how academics analyse the arguments, some commenters might want to modify their approach… who knows?

The comment threads they looked at (I think) are from five posts from Feb to April 2019, including The best case for worst case scenarios, Nenana Ice Classic 2019, First successful model simulation of the past 3 million years and a couple of open threads.

  1. C.W. van Eck, B.C. Mulder, and A. Dewulf, "Online Climate Change Polarization: Interactional Framing Analysis of Climate Change Blog Comments", Science Communication, vol. 42, pp. 454-480, 2020.
Categories: Blogtastic

Climate Sensitivity: A new assessment

Wed, 07/22/2020 - 14:00

Not small enough to ignore, nor big enough to despair.

There is a new review paper on climate sensitivity published today (Sherwood et al., 2020 (preprint) that is the most thorough and coherent picture of what we can infer about the sensitivity of climate to increasing CO2. The paper is exhaustive (and exhausting – coming in at 166 preprint pages!) and concludes that equilibrium climate sensitivity is likely between 2.3 and 4.5 K, and very likely to be between 2.0 and 5.7 K.

For those looking for some context on climate sensitivity – what it is, how can we constrain it from observations, and what observations are available, browse our previous discussions on the topic: On Sensitivity, Sensitive but Unclassified Part 1 + Part 2, A bit more sensitive, and Reflections on Ringberg among others. In this post, I’ll focus on what is new about this review.

Figure 1. The dependence between different constraints on the inferred sensitivity (S). Circles denote uncertain variables, while square denote (independent) evidence. The Bayesian process samples the uncertainties and the best sets of parameters that match all the evidence are then examined to see what they imply for S.

Climate Sensitivity is constrained by multiple sets of observations

The first thing to note about this study is that it attempts to include relevant information from three classes of constraints: processes observed in the real climate, the historical changes in climate since the 19th Century, and paleo-climate changes from the last ice age (20,000 years ago) and the Pliocene (3 million years ago) (see figure 1). Each constraint has (mostly independent) uncertainties, whether in the spatial pattern of sea surface temperatures, or quality of proxy temperature records, or aerosol impacts on clouds, but the impacts of these are assessed as part of the process.

Importantly, all the constraints are applied to a coherent, yet simple, energy balance model for the climate. This is based on the standard ‘temperature change = energy in – energy out + feedbacks’ formula that people have used before, but it explicitly tries to take into account issues like the spatial variations of temperature, non-temperature-related adjustments to the forcings, and the time/space variation in feedbacks. This leads to more parameters that need to be constrained, but the paper tries to do this with independent information. The alternative is to assume these factors don’t matter (i.e. set the parameters to a fixed number with no uncertainty), and then end up with mismatches across the different classes of constraints that are due to the structural inadequacy of the underlying model.

This is fundamentally a Bayesian approach, and there is inevitably some subjectivity when it comes to assessing the initial uncertainty in the parameters that are being sampled. However, because the subjective priors are explicit, they can be adjusted based on anyone else’s judgement and the consequences worked out. Attempts to avoid subjectivity (so-called ‘objective’ Bayesian approaches) end up with unjustifiable priors (things that no-one would have suggested before the calculation) whose mathematical properties are more important than their realism.

What sensitivity is being constrained?

There are a number of definitions of climate sensitivity in the literature, varying depending on what is included, and how easy they are to calculate and to apply. There isn’t one definition that is perfect for each application, and so there is always a need to translate between them. For the sake of practicality and to not preclude increases in scope in climate models, this paper focuses on the Effective Climate Sensitivity (Gregory et al, 2004) (based on the 150 yr response to an abrupt change to 4 times CO2), which is a little smaller than the Equilibrium Climate Sensitivity in most climate models (Dunne et al, 2020). It can allow for a wider range of feedbacks than the standard Charney sensitivity, but limits the very long term feedbacks because of its focus on the first 150 years of the response.


Each class of constraint has it’s own issues. For the paleo-climate constraints, the uncertainties relate to the fidelity of the temperature reconstructions and knowledge of the forcings (greenhouse gas levels, ice sheet extent and height, etc). Subtler issues are whether ice sheet forcing has the same impact as greenhouse gas forcing per W/m2 (e.g. Stap et al., 2019), and whether there is an asymmetry between colder and warmer climates than today. For the transient constraints, there are questions about the difference between the pattern of sea surface temperature change over the last century compared to what we’ll see in long term, and the implications of aerosol forcing over the twentieth century which is still quite uncertain.

The process-based constraints, sometimes called emergent constraints, face challenges in enumerating all the relevant processes and finding enough variability in the observational records to assess their sensitivity. This is particularly hard for cloud related feedbacks – the most uncertain part of the sensitivity.

The paper goes through each of these issues in somewhat painful detail, highlighting as it does so areas that could do with further research.

Putting it together

There have been a few earlier papers that tried to blend these three classes of constraints, notably Annan and Hargreaves (2006), but doing so credibly while accounting for possible shared assumptions has been difficult. This paper explicitly looks at the sensitivity to the (subjective) priors, the quality of the evidence, and reasonable estimates of missing information. Notably, the paper also addresses how wrong the assumptions would need to be to have a notable impact on the final results.

Figure 2. PDFs of S in comparison with AR5. The Baseline PDF is shown in black, and its 66% range (2.6-3.9 K) in grey. Colored curves show PDFs from sensitivity tests which cover a range for S which could plausibly arise given reasonable alternative assumptions or interpretations of the evidence, summarized by the magenta line (2.3-4.5 K). The “likely” range from AR5 (1.5-4.5 K) is shown in cyan. Circles indicate 17th and 83rd percentile values.

Bottom line

The likely range of sensitivities is 2.3 to 4.5 K, which covers the basic uncertainty (“the Baseline” calculation) plus a number of tests of the robustness (illustrated in Figure 2). This is slightly narrower than the likely range given in IPCC AR4 (2.0-4.5 K), and quite a lot narrower than the range in AR5 (1.5-4.5 K). The wider range in AR5 was related to the lack (at that time) of quantitative explanations for why the constraints built on the historical observations were seemingly lower than those based on the other constraints. In the subsequent years, that mismatch has been resolved through taking account of the different spatial patterns of SST change and the (small) difference related to how aerosols impact the climate differently from greenhouse gases.

This range the paper comes up with is not a million miles from what most climate scientists have been saying for years. That a group of experts, trying their hardest to quantify expert judgement, comes up with something close to the expert consensus perhaps isn’t surprising. But, in making that quantification clear and replicable, people with other views (supported by evidence or not) now have the challenge of proving what difference their ideas would make when everything else is taken into account.

One further point. When this assessment started, it was before anyone had seen any of the CMIP6 model results:

As many have remarked, some (but not all) reputable models have come out with surprisingly high climate sensitivities, and in comparison with the likely range proposed here, about a dozen go beyond 4.5 K. Should they therefore be ruled out completely? No, or at least not yet. There may be special combinations of features that allow these models to match the diverse observations while having such a high sensitivity. While it may not be likely that they will do so, they should however be tested to see whether or not they do. That means that it is very important that these models are used for paleo-climate runs, or at least idealised versions of them, as well as the standard historical simulations.

In the meantime, it’s certainly worth stressing that the spread of sensitivities across the models is not itself a probability function. That the CMIP5 (and CMIP3) models all fell within the assessed range of climate sensitivity is probably best seen as a fortunate coincidence. That the CMIP6 range goes beyond the assessed range merely underscores that. Given too that CMIP6 is ongoing, metrics like the mean and spread of the climate sensitivities across the ensemble are not stable, and should not be used to bracket projections.

The last word?

I should be clear that although (I think) this is the best and most thorough assessment of climate sensitivity to date, I don’t think it is the last word on the subject. During the research on this paper, and the attempts to nail down each element of the uncertainty, there were many points where it was clear that more effort (with models or with data analysis) could be applied (see the paper for details). In particular, we could still do a better job of tying paleo-climate constraints to the other two classes. Additionally, new data will continue to impact the estimates – whether it’s improvements in proxy temperature databases, cloud property measurements, or each new year of historical change. New, more skillful, models will also help, perhaps reducing the structural uncertainty in some of the parameters (though there is no guarantee they will do so).

But this paper should serve as a benchmark for future improvements. As new data comes in, or better understandings of individual processes, the framework set up here can be updated and the consequences seen directly. Instead of claims at the end of papers such as “our results may have implications for constraints on climate sensitivity”, authors will be able to work them out directly; instead of cherry-picking one set of data to produce a conveniently low number, authors will be able to test their assumptions within the framework of all the other constraints – the code for doing so is here. Have at it!

  1. S. Sherwood, M.J. Webb, J.D. Annan, K.C. Armour, P.M. Forster, J.C. Hargreaves, G. Hegerl, S.A. Klein, K.D. Marvel, E.J. Rohling, M. Watanabe, T. Andrews, P. Braconnot, C.S. Bretherton, G.L. Foster, Z. Hausfather, A.S.V.D. Heydt, R. Knutti, T. Mauritsen, J.R. Norris, C. Proistosescu, M. Rugenstein, G.A. Schmidt, K.B. Tokarska, and M.D. Zelinka, "An assessment of Earth's climate sensitivity using multiple lines of evidence", Reviews of Geophysics, 2020.
  2. J.M. Gregory, "A new method for diagnosing radiative forcing and climate sensitivity", Geophysical Research Letters, vol. 31, 2004.
  3. J.D. Annan, and J.C. Hargreaves, "Using multiple observationally-based constraints to estimate climate sensitivity", Geophysical Research Letters, vol. 33, 2006.
Categories: Blogtastic

Shellenberger’s op-ad

Thu, 07/09/2020 - 14:43

Guest commentary by Michael Tobis

This is a deep dive into the form and substance of Michael Shellenberger’s promotion for his new book “Apocalypse Never”. Shorter version? It should be read as a sales pitch to a certain demographic rather than a genuine apology.

Michael Shellenberger appears to have a talent for self-promotion. His book, provocatively entitled “Apocalypse Never” appears to be garnering considerable attention. What does he mean by that title? Does it mean we should do whatever we can to avoid an apocalypse? Does it mean that no apocalypse is possible in the foreseeable future? For those of us who haven’t yet read the book (now available on Kindle), Shellenberger provides an unusual article (at first posted on Forbes, then at Quillette and the front page of the Australian) which appears less a summary than a sales pitch, an “op-ad” as one Twitter wag put it.

It’s called “On Behalf Of Environmentalists, I Apologize For The Climate Scare”. In short, Shellenberger lands clearly on the naysayer soil. Not much to see, everyone. Cheer up, carry on, these are not the droids you’re looking for.


In support of this insouciance, Shellenberger offers twelve “facts few people know”. Most of the points are defensible to some extent, and most of them raise interesting topics. A main purpose of this article is to provide references to the relevant discussions. But in going through it, it’s worth keeping an eye on the rhetorical purposes of the items, which appear a bit scattershot, and to the rhetorical purpose of the list, which might appear rather obscure.

Clearly labeling the list “facts that few people know” implies that all these points unambiguously refute common beliefs that are widely. And the “apology for the climate scare” indicates further that these beliefs are widely held by a supposedly misguided community of “climate scared”. A defender of the list, Blair King suggests that “[Shellenberger] identified false talking points used repeatedly by alarmists to misinform the public and move debate away from one that is evidence-based to one driven by fear and misinformation”. That does seem to be a fair reading of the stated intent of the list, but it just doesn’t ring true as a whole.

Speaking as a verteran “climate scared” person, the items don’t seem especially familiar. It’s hard to imagine a conversation like this:“Gosh, climate change is an even bigger threat to species than habitat loss.”“I know, and the land area used for producing meat is increasing!”As Gerardo Ceballos said:

This is not a scientific paper. It is intended, I guess, to be an article for the general public. Unfortunately, it is neither. It does not have a logical structure that allows the reader to understand what he would like to address, aside from a very general and misleading idea that environmentalists and climate scientists have been alarmist in relation to climate change. He lists a series of eclectic environmental problems like the Sixth Mass Extinction, green energy, and climate disruption. And without any data nor any proof, he discredits the idea that those are human-caused, severe environmental problems. He just mentions loose ideas about why he is right and the rest of the scientists, environmentalists, and general public are wrong.

What causes the strange incoherence of these “facts few people know”? At the end of this review I’ll propose an answer. Meanwhile, I will consider several questions regarding each item:

  • VALIDITY Is the claim unambiguously true? Unambiguously false? Disputed?
  • RELEVANCE TO CLIMATE Is the claim directly relevant to climate concern/”climate scare” or is it more of interest to tangentially related environmental issues?
  • SALIENCE Is the contrary of the claim widely believed by environmental activists? Does widespread belief in the claim contribute materially to an excess of climate concern?
  • IMPLICATION What is the rhetorical purpose of the question?
  • REALITY To what extent is the rhetorical purpose justified?


1) Humans are not causing a “sixth mass extinction”

In a literal sense this claim has its defenders. See “Earth is Not In the Middle of a Sixth Mass Extinction”. The article quotes Smithsonian paleontologist Doug Erwin, who wrote to me in an email:.

Many of those making facile comparisons between the current situation and past mass extinctions don’t have a clue about the difference in the nature of the data, much less how truly awful the mass extinctions recorded in the marine fossil record actually were.

It is absolutely critical to recognize that I am NOT claiming that humans haven’t done great damage to marine and terrestrial [ecosystems], nor that many extinctions have not occurred and more will certainly occur in the near future. But I do think that as scientists we have a responsibility to be accurate about such comparisons…

I think that if we keep things up long enough, we’ll get to a mass extinction, but we’re not in a mass extinction yet, and I think that’s an optimistic discovery because that means we actually have time to avoid Armageddon

I leave it to the reader as to whether “not in a mass extinction yet” is reassuring. While there are several possible understandings of “mass extinction”, it’s generally agreed that we are indeed losing species at a rapid rate. Erwin is pointing out that the vast majority of life isn’t collapsing, that we aren’t collapsing into a nearly lifeless planet “Yet.” Will people reading Shellenberger’s quote get the message “we’re not in a mass extinction yet, … we actually have time to avoid Armageddon”? I venture that if they read about it in a book called “Apocalypse Never” they won’t. Is this related to something we might call “The Climate Scare”? Not yet. Climate is only a secondary feature of species loss so far, although there are plenty of signs of a climate impact in what’s left of natural ecosystems.

  • VALIDITY – Valid only provisionally and somewhat of a semantic quibble.
  • RELEVANCE TO CLIMATE – Speculative; if we don’t get a handle on climate change, climate change will make it worse.
  • SALIENCE – This one is genuinely scary, so it’s okay to be scared about it.
  • IMPLICATION – You are presumably meant to read this claim as “This talk about a sixth extinction is typical climate alarmist scaremongering”
  • REALITY – We are not literally in a mass extinction event yet but we are on the brink of one. It’s not really a “climate scare” topic but it’s related, and enormous. It seems utterly bizarre for someone claiming to speak “on behalf of environmentalists” to minimise it.

2) The Amazon is not “the lungs of the world”

It’s fair to say that “the Amazon is the lungs of the world” is an environmentalist talking point. It’s fair, I think, to say that some members of the public are afraid of killing enough trees that we run out of oxygen (never mind that lungs consume oxygen rather than producing it!). It turns out that what maintains the oxygen fraction in the atmosphere is a rather interesting question, but that there is no immediate risk of the oxygen going away. Here’s a paper (w/thanks to Chris Colose).

We have built up an enormous stockpile of the stuff. If we live long enough that the oxygen concentration changes appreciably, we will have survived the current century and many centuries to come. Is it a reason to NOT preserve the Amazon? Hardly. The Amazon is the repository for much of the land surface biodiversity. A better analogy would be that it’s more like our planetary gut than our planetary lungs. It would be stupid beyond belief to injure it, yet injure it we do. Does the fear of disappearing oxygen feed excessive “environmentalist” panic? Arguably so among the more excitable members of the general public sharing half-baked ideas on social media. But is it part of “The Climate Scare”? It’s a bit of a stretch. One could point out, though, that totally clearing the Amazon would have direct impacts on climate, according to several modeling studies, for instance.

  • VALIDITY – The claim is meaningless, so the counterclaim is meaningless
  • RELEVANCE – It’s a pretty muddled belief, but it could conceivably be seen as climate related.
  • SALIENCE – In fact there is baseless alarm about the Amazon’s ability to provide oxygen
  • IMPLICATION – “Don’t lose sleep about the Amazon; it’s not important.”
  • REALITY – The Amazon is the repository of an enormous amount of biodiversity that is at risk. Truly destroying it entirely would have climate impacts. Saving it is an important issue. But not because of oxygen!

3) Climate change is not making natural disasters worse

Roger Pielke Jr. enters the fray. This claim is obviously based on his position which Roger helpfully summarizes in a recent Twitter thread

First, what is a disaster?
A disaster refers to impacts
By themselves, eg, an earthquake or hurricane is not a disaster
For humans we typically measure impacts in lives lost or economic losses (obviously there are other metrics)
This is the definition of the IPCC

— Roger Pielke Jr. (@RogerPielkeJr) July 4, 2020

This is a very specific definition of “disaster” which Roger defends vigourously. One suspects that he does so precisely because the signal is buried in the noise in his definition. It’s a definition that could hardly have been better designed to avoid statistical significance!

I wrote more about that here. Take note: Pielke only claims “there is no statistical evidence that disasters are getting worse” while Shellenberger states “disasters are not getting worse”. A classic conflation of “absence of evidence” with “evidence of absence”. In addition, Pielke’s claim only stands because the rising costs of disasters have been normalized by the rise in GDP. It is entirely unclear why this is the relevant metric. Shellenberger’s claim, despite Pielke’s defense of it, is not defensible by reference to Pielke.

  • VALIDITY: Shellenberger’s claim goes too far even based on Pielke’s significance-averse approach.
  • RELEVANCE: relevant to climate change impact
  • SALIENCE: Yes, people do worry about it a lot. Perhaps a bit too soon, but it’s not an unrealistic concern.
  • IMPLICATION: “No sign of a problem!”
  • REALITY: There are many signs that several types of severe events (notably heatwaves, drought impacts, and intense precipitation) are becoming more common and more severe.

4) Fires have declined 25 percent around the world since 2003

After the nitpicking of points 1 and 3, it’s very interesting to see the fuzziness here. It is true that total annual area burned worldwide has declined. But this is because grass fires have declined, because of increasing human appropriation of grasslands for agriculture. Forest fires, which are more ecologically damaging than grass fires, have increased.

While NASA’s new video does show regional upticks in certain parts of the world, scientists made clear that the total number of square kilometers burned globally each year has dropped roughly 25 percent since 2003. This has largely been due to population growth and development in grasslands and savannas, as well as to an increase in the use of machines to clear farmland. “There are really two separate trends,” said James Randerson, a scientist at the University of California, Irvine who worked on the new wildfire video. “Even as the global burned area number has declined because of what is happening in savannas, we are seeing a significant increase in the intensity and reach of fires in the western United States because of climate change.”

So, areas and intensity of forest fires have increased, and this claim is simply misdirection by mixing two phenomena, increasing forest fires and increasing human footprint on grasslands. The concern about increases in forest fires is valid.

  • VALIDITY: Misleading. Conflates two anthropogenic phenomena into one.
  • RELEVANCE: relevant to climate change impact
  • SALIENCE: Yes, people do worry about it a lot. Justifiably.
  • IMPLICATION: “See? Climate activists are deluded about wildfires.”
  • REALITY: Forest fires do appear to be increasing in frequency and severity. This is unsurprising as forests are exposed to warmer conditions that the ones for which they evolved, so are more prone to drying out.

5) The amount of land we use for meat—humankind’s biggest use of land—has declined by an area nearly as large as Alaska

This turns out to be a defensible claim. But it’s not such a happy result. “this contraction is mostly in arid regions where scrubland was used for extensive low impact grazing. Some of the declines in these regions have been offset by expansions of grazing in tropical regions where the environmental destruction is immense e.g. in the Amazon. This “livestock revolution” has come with consequences associated with the spreading of fertilizers, and the draining of ecologically sensitive wetlands.” Regardless, as a careful examination of the vertical axis on the graph shows, on a percentage basis it’s small.

Finally, from personal experience I would point out that. at least in central Texas, much pasture land has been abandoned because it was ruined by overgrazing. I expect it’s similar elsewhere. Returning denuded limestone to “nature” is not that great of a gift.

  • VALIDITY: Marginal. Made out as an important trend when it’s really not.
  • RELEVANCE: No obvious relevance to climate.
  • SALIENCE: I don’t think this is a prominent concern among environmentalists at large.
  • IMPLICATION: ??? (It’s unclear what purported “alarmist idea” this counters.)
  • REALITY: The impacts of meat production are elsewhere.

6) The build-up of wood fuel and more houses near forests, not climate change, explain why there are more, and more dangerous, fires in Australia and California

It’s undisputed that fire suppression has built up fuel in many places, and that people have built housing in dangerously fire-prone locations. It’s also undisputed that the recent fires in Australia, as well as spectacular events in Russia in 2010 and Texas in 2011, occurred in conditions of literally unprecedented heat and drought. Of course, fires happen in hot dry years. But we’re seeing an obvious trend in such outliers. Things can have more than one cause.

  • VALIDITY: As stated, literally false. Things can have more than one contributing factor.
  • RELEVANCE: climate impact relevant
  • SALIENCE: People worry about this, and they should
  • IMPLICATION: “Hot weather doesn’t make forests burn because fire suppression makes forest burn, so don’t worry about climate change!”
  • REALITY: Unsurprisingly, forests are more likely to dry out and burn when it’s hotter.

7) Carbon emissions are declining in most rich nations and have been declining in Britain, Germany, and France since the mid-1970s

This is true. In some countries it is quite substantial. It has two primary causes: 1) Recent declines in coal consumption, mostly replaced by natural gas. Since climate stability is only achieved at net zero emissions, investment in gas infrastructure is a mixed blessing. 2) Much industrial activity moving to Asia, especially China. This is just moving the problem, not solving it. It’s “global warming”, not “national warming”. If you look at the global trajectory rather than that of individual countries, emissions continue to burgeon. Even the recent pandemic related events appear so far to have been very temporary. If you compare what is happening now to the path required to limit warming to any particular target, especially 2ºC or better, it’s very hard to take this little bit of good news with too much jubilation.

Annual CO2 emissions by region

Sam Bliss points out that no rich country is reducing emissions fast enough to keep global warming under 2ºC — or even planning to.

No rich country is reducing emissions fast enough to keep global warming under 2C — or even planning to. The UK and Sweden have committed to reduction pathways that entail twice their fair share of carbon emissions, according to @KevinClimate et al.

— Sam Bliss (@ii_sambliss) July 2, 2020

  • VALIDITY: True, but something of a cherry pick
  • RELEVANCE: climate relevant, but the narrow claim is nowhere near as important as is implied
  • SALIENCE: I don’t know that people are worried about small declines in emissions records of particular countries. People are certainly worried about global totals, though.
  • IMPLICATION: “We’re already fixing the problem! Relax!”
  • REALITY: We are still very far from fixing the problem, and the hard-won but modest progress in a few wealthy countries is not reassuring.

8) “The Netherlands became rich, not poor while adapting to life below sea level”

First, we should probably neglect point 8 altogether, since it is commonly known that the Dutch have done well over the centuries, and that they have won back a fair piece of land from their continental shelf. So it doesn’t qualify as something “few people know”. It’s sloppy to include it on the list.

Clearly the implication that “alarmists say the Dutch are not wealthy!” is just nonsense. What about “alarmists say the Dutch are drowning”? I’ve not heard that one either. So logically speaking we can ignore this point. Is this merely silly? Can Shellenberger be claiming that bad news is good news? That we should embrace climate change because it will build character? Is this the quality of argument that we’re facing?

Homeowners in Ocean County, NJ are early recipients of the stimulus to creativity and economic activity of sea level rise, in the aftermath of Hurricane Sandy. USGS

Let’s bend over backwards to consider the matter. It appears that the point is that at least one society has adapted to life below sea level; so we all can do that. But does that really mean that the Dutch are prepared to adapt to sea level rise of meters? There are two approaches to thinking about the Dutch situation in the future. Some are bravely advocating a “make lemonade” approach, inclining toward the insouciant “disasters are business opportunities” framing that Shellenberger implies. But others which look in deeper detail are more sobering:

Of course, dikes are being raised, and rivers given some room to overflow occasionally, but will that be enough? And more importantly: how long will it last? Sea levels have only just started to rise, and it may be going faster than we had initially thought. The big question is: will the Netherlands as we know it survive what’s coming?

In order to keep the seawater at bay, the dikes will need to be raised. As a result, the polders behind them will become relatively deeper, making them more vulnerable and more expensive to maintain. These higher dikes are also a problem in themselves: they prevent natural silting, which means our delta is unable to grow along with the advancing sea.

The experts share one concern: the Netherlands has no Plan B for a scenario in which sea levels rise faster than are accounted for in the Delta Programme. At the same time, there is no proper public debate about this issue, despite the urgent need for one. Not sometime in the future, but right now – because we need to make some important choices today. Especially if you consider how long it takes to develop and implement plans.

Reducing CO<sub>2</sub> emissions and reinforcing dikes is only half the story. The other stark reality is that even these measures combined may prove insufficient in the long term to preserve the lower-lying parts of our country. The polder model – in its literal rather than political sense – has its limits, some physical and some more subjective. The physical limits are based on hard science: how quickly will sea levels rise – and how much can we actually handle? The subjective limits are a question of taste: what kind of country do we want to live in (while we still have time to decide)?

Can we adapt to sea level rise? The implication of this point is that we can adapt like the Dutch. But can the Dutch, who are the world’s experts on managing land below sea level adapt? Only, it appears, within limits.

  • VALIDITY: Undisputed. Indeed, hard to imagine why this qualifies as a “fact few people know”!
  • RELEVANCE: relates indirectly to climate impacts
  • SALIENCE: People do worry about sea level rise, and they should
  • IMPLICATION: “Sea level rise is harmless since humans can rise to the occasion of great challenges.”
  • REALITY: Even the Dutch, wealthy and experienced in managing coastal flooding, are very worried.

9) We produce 25 percent more food than we need and food surpluses will continue to rise as the world gets hotter

This is a bit controversial, but I think Shelleberger is correct. Large scale agriculture can adapt to changing conditions. Crop failures in one place or another may become more frequent as climate becomes less predictable and in some ways more severe, but global production will probably remain adequate for a long time, provided the current economic and trade regime remains healthy. A survey article is here. The impacts of climate change on food supply, except on the poorest, is expected to be relatively modest, compared to other scenario variables:

Finally, all quantitative assessments we reviewed show that the first decades of the 21st century are expected to see low impacts of climate change, but also lower overall incomes and still a higher dependence on agriculture. During these first decades, the biophysical changes as such will be less pronounced but climate change will affect those particularly adversely that are still more dependent on agriculture and have lower overall incomes to cope with the impacts of climate change. By contrast, the second half of the century is expected to bring more severe biophysical impacts but also a greater ability to cope with them. The underlying assumption is that the general transition in the income formation away from agriculture toward nonagriculture will be successful.

How strong the impacts of climate change will be felt over all decades will crucially depend on the future policy environment for the poor. Freer trade can help to improve access to international supplies; investments in transportation and communication infrastructure will help provide secure and timely local deliveries; irrigation, a promotion of sustainable agricultural practices, and continued technological progress can play a crucial role in providing steady local and international supplies under climate change.

This said, climate change will have an enormous impact on traditional food-gathering and subsistence agriculture. Traditional methods will fail. Greenland is a harbinger. If traditional cultures and folkways are valuable, their food gathering and subsistence methods are central. These are being lost.

  • VALIDITY: Plausible
  • RELEVANCE: relevant to climate change
  • SALIENCE: I think there is a strong case that there’s too much public alarm on the climate- food security axis.
  • IMPLICATION: “Food is not a big climate issue!”
  • REALITY: If the international economic order holds together, enough nutrients to feed everyone will be produced in the foreseeable future. But climate change impacts on traditional cultures are already severe and will likely eventually be overwhelming. Distributional issues may leave people hungry even as enough food is produced in aggregate.

10) Habitat loss and the direct killing of wild animals are bigger threats to species than climate change

It’s not clear how to formally evaluate this claim. It is surely true of some species and not of others. Coral reef species, for example, are under direct threat from ocean acidification and local warming events. Habitat loss can certainly be exacerbated by climate change. Here, the recent example of Australian fires is instructive. These phenomena can’t be directly separated. Climate change causes habitat loss.

The main way in which climate stress affects natural species is through habitat loss via climate niche moves and disappearance. It isn’t at all clear that the comparison between habitat loss and climate stress, even if it were possible, would be very informative. You can’t really protect wildlife without protecting or creating stable habitat. Under rapid climate change that becomes impossible.

  • VALIDITY: The assertion is overly broad and probably untestable.
  • RELEVANCE: climate relevant
  • SALIENCE: People do worry about habitat and people do worry about climate; sometimes they get them confused, and sometimes they are related. It’s not clear concerns are excessive
  • IMPLICATION: “Climate change is not a problem for wildlife!”
  • REALITY: Climate change is a major driver of habitat loss, so if you care about habitat, you should care about climate policy.

11) Wood fuel is far worse for people and wildlife than fossil fuels

This conflates several issues.

  1. Wood-burning ovens and grills in wealthy countries are a carbon neutral luxury of no great biogeochemical importance. There is no controversy on this matter that I know of.
  2. Biofuels are carbon neutral. Although it is a relatively minor source of energy, extracting energy from burning wood waste is better than simply letting the waste decay, producing the same CO2 without capturing the energy. However, mis-designed carbon credit systems in Europe have been encouraging growing trees specifically for the purpose of burning them. While carbon-neutral in the long run, this use produces carbon in the short run and consumes it on a longer time scale, front-loading emissions. It is a carbon-overshoot strategy, and there’s a strong case to be made that given our present trajectory toward exceeding global warming targets, it’s a bad idea. However, on this matter, one would tend to see the most “climate alarmed” as aligned with Shellenberger, not opposed, so it doesn’t support his case.
  3. Wood-burning for home cooking in less developed countries is a real health issue. This is certainly true, but no important group is advocating household wood fuel as a mainstay for large populations that I know about. It’s possible to imagine an innumerate anti-technology Luddite advocating returning to wood-burning stoves, but it’s difficult to imagine that gaining much purchase, insofar as forests are greatly valued, if not even overvalued, by climate activists. So on these points, Shellenberger is probably better aligned with “climate activists” than against them.
  • VALIDITY: The claim is true, especially insofar as low-technology wood-burning is concerned.
  • RELEVANCE: Not first order climate relevant. Nobody is proposing replacing fossil fuels with wood burning on a global scale.
  • SALIENCE: The biofuel issue is a real controversy and second order relevant to the climate problem, but modern biofuel plants not a major health concern, certainly compared to coal plants. The use of wood-burning in households is a real health issue, but not climate relevant. Shellenberger is probably better aligned here with “climate activists” than against them.
  • IMPLICATION: Hard to know. Maybe “the environmental crazies want to take away your furnace and put a nasty sooty wood-burning hearth in your kitchen.”
  • REALITY: Poor wood burning practice in households is indeed unhealthy, but carbon neutral. The issue of biomass burning is complex; some uses are better than others. Growing wood specifically for fuel has deleterious impacts on the carbon trajectory, and is probably not a great idea, even though the strategy is basically long-term carbon neutral.

12) Preventing future pandemics requires more not less “industrial” agriculture

There seems to be a case being made that CAFOs (Confined Animal Feeding Operations) are less dangerous than pastures on this account. My initial investigations on the subject turned up a lot of evidence against Shellenberger’s claim.

I finally turned up what must be Shellenberger’s source. This piece is attributed to the young Alex Smith – Alex joined Breakthrough as a research analyst in the food and agriculture program in 2019 after completing a dual MA/MSc in International and World History from Columbia University and the London School of Economics and Political Science. In his masters, Alex studied and wrote about American foreign policy, French colonialism, and environmental history.  In short, Mr Smith doesn’t seem to have much formal knowledge about pandemics or agriculture. He concludes:

With our global population set to increase by close to 3 billion by 2050, we must strive to construct a world that can provide food, shelter, and livelihoods to all 10 billion people, while reducing risk of pandemics akin to what we see today. Simply, the only way forward is forward. We must continue to develop agricultural innovations that can allow for increased intensification, and we must give these innovations global reach. It does not work to just intensify agricultural production in developed countries, given the dual role of land-use change and food insecurity. To combat the main drivers of zoonotic diseases, we must sustainably intensify our food system, not pine for a romanticized and inefficient production system that brings people and wild animals in closer contact.

Frankly, this reminds me of the Monty Python sketch that teaches you how to play the flute. Smith dismisses the obvious solution in his second paragraph:

But these claims offer no explicit argument for how a different form of agriculture — outside of calls to completely eliminate meat consumption — would reduce risk, and they often conflate intensive animal agriculture with intensive agriculture writ large.

I myself have indeed given up on animal products almost altogether (I do have a weakness for butter-based desserts at cafés that I occasionally indulge) so I can’t resist noting this dodge. I don’t see any reason meat can’t go back to being an occasional luxury as it was through most of human history. But this is hardly the place for that discussion. To the point, Shellenberger seems to be putting up basically a blog post by a young man with a history degree against the entire field of epidemiology, and declaring “a fact” on that basis. I’d call that a stretch.

  • VALIDITY: The claim is very weakly supported and probably wrong.
  • RELEVANCE: No obvious climate relevance
  • SALIENCE: I think people do, sensibly, worry about the way meat is produced
  • IMPLICATION: “Coop up animals in meat factories! It’s good for you and they don’t mind much.”
  • REALITY: Er, no.


It’s very hard to imagine a significant community of people adamantly holding to the contrary of Shellenberger’s points. They really aren’t core to any particular group.So what is he up to, if it’s more than just selling a book?

Is this the problem, then? Half-truths, incoherent cases, sound-good arguments that in total don't add up to a coherent case against environmentalism except seemingly on 4-minute between-commercial segments on conservative talk radio but not in thought-out rational discourse?

— David Appell (@davidappell) July 2, 2020

I think David hits the nail on the head. It’s a pitch to denialism, not to moderation. But why is is so strangely constructed, so uncompelling to some of us, and yet apparently convincing to others? There’s a provocatively titled article at The Forward that has an answer:

The fuel for this fire comes from something that anthropologists call the myth of outgroup homogeneity. We tend to believe everyone in our tribe is nuanced and diverse, while all the members of that tribe over there are uniform and zombie-like. This is how New York thinks of New Jersey, Lakers fans think of Clippers fans, Mac users think of PC users, and MSNBC viewers think of Fox News viewers. The outgroup homogeneity effect makes it easier to blame a whole side for their crazy fringe while barely acknowledging your own. You can march under a big dumb banner, saying you’re from the smart, nuanced part of your coalition, while believing everyone on the other side has no more profound beliefs than their big, dumb banner.

Shellenberger’s weird list makes no sense at all. It certainly doesn’t bear up well under close inspection. But it makes some sense to his readers, only because they perceive the world of the climate concerned as “uniform and zombie-like”. Every single point of contention he raises is viewed through that lens first.

Is Shellenberger really even a “former environmentalist”? Has he ever actually advocated a “climate scare”? Does he have anything to apologise for? The evidence for his (oddly un-contrite) apostasy is thin. His list, baffling to those of us it is meant to accuse, holds together as an example of “outgroup homogeneity”. Shellenberger’s capacity to frame a list this way depends on a capacity to grossly oversimplify his “climate scare” opposition. His baffling caricature of his opposition would indicate that he never really was part of a “climate scare” in the first place!
The article, remember, is entitled “On Behalf Of Environmentalists, I Apologize For The Climate Scare”. I suggest Shellenberger in innocent on that score. He may however owe us a different apology.

Categories: Blogtastic

Unforced Variations: July 2020

Thu, 07/02/2020 - 02:01

This month’s open thread for climate science topics.

Categories: Blogtastic

Sensitive but unclassified: Part II

Sat, 06/13/2020 - 12:34

The discussion and analysis of the latest round of climate models continues – but not always sensibly.

In a previous post, I discussed the preliminary results from the ongoing CMIP6 exercise – an international, multi-institutional, coordinated and massive suite of climate model simulations – and noted that they exhibited a wider range of equilibrium climate sensitivities (ECS) than in previous phases (CMIP5 and earlier) and wider than the assessed range based on observational constraints (of many kinds).

Since then, more model results have been added to the archive, and thanks to Mark Zelinka, we can see some of the analysis as it updates in real time.

By eye, it looks like there are two (or three) groups of models, one within the range of the assessed values (roughly 2 to 4.5ºC), one group with significantly higher values, and one institution/two models with a notably lower ECS. The question everyone has is whether this extended range is credible.

Mark and colleagues recent paper (Zelinka et al., 2020) demonstrated that a big part of the reason for the high sensitivities was in the Southern Ocean cloud feedback:

This is the key result from the Zelinka et al paper that just appeared. It shows that the big difference in sensitivities in some of the CMIP6 models is tied to the short wave low cloud feedbacks in the Southern Oceans (orange line).

— Gavin Schmidt (@ClimateOfGavin) January 4, 2020

Since my first post, there have been a number of papers have looked at the skill of these models to see whether there are some key observational data that might help in constraining the sensitivity (and by extension, the projections into the future). One set of papers has focused on the global mean trends from 1990 or so onward which is a period of stable or declining aerosol trends and which might therefore be a closer test of the models’ transient sensitivity to CO2 than earlier periods. Notably Tokarska et al. (2020) and Njisse et al. (2020) suggest that many of the high ECS group warm substantially faster than observed over this period and therefore should be downweighted in the constrained projections of the future.

From Nijsse et al (2020).

Recently however, writing in Guardian, Jonathan Watts uses results from the UK’s new model (Williams et al., 2020) and a commentary from Tim Palmer to argue that that we nonetheless need to take these high sensitivities more seriously, and indeed that they may indicate that the assessed ECS range has been underestimating potential changes in the future. This is however flawed.

The Williams et al paper demonstrates that updates to the HadGEM3‐GC3.1 model developed by the UK’s Hadley Centre that affect the clouds and aerosols, increase the skill of that model in short-term initialized weather forecasts. This is fine, and indeed, consistent with increases in skill in the newer models across the board when they are compared to a very broad range of observations.

But it is a logical leap to go from an observation of increased skill in one metric to assuming that therefore the overall ECS in this particular model is more likely. To demonstrate that, one would need to show that this particular measure of skill was specifically related to ECS which has not been done (a point Palmer acknowledges). To put in another way, it may be that all models that do well on this task have a range of ECS values, and that the coincidence of this one model doing well and having a high ECS, was just that, a coincidence.

The Williams et al paper and Palmer commentary point to one particular feature of this model which is that the newer (higher ECS) versions have greater amounts of cloud liquid water at cold temperatures. For background, clouds can consist of either ice crystals, or liquid water droplets which have quite different radiative behaviours (liquid water clouds are generally more reflective), and knowing whether clouds are ice or water has been historically difficult to determine globally. In recent years however, satellite data from CloudSAT/CALIPSO has shown that more clouds have liquid water and at colder temperatures than was assumed before, and hence newer models have reflected that updated information.

This has an impact on ECS because in a warming world, one expects more cloud water to turn from ice to liquid, and since liquid clouds are more reflective, this is a damping feedback on overall climate warming. But if there is less cloud ice around, then there will be less of that ice to turn to water, and thus the magnitude of this damping effect will be smaller, and thus the overall sensitivity will be higher.

In discussions with colleagues over the last few months, this effect has been frequently brought up as a potential reason to think that the higher ECS values are therefore justified. But closer analysis does not necessarily support this. Some models for instance, have increased their cloud liquid water but have only had modest increases in climate sensitivity. Thus the relationship between higher CLW and ECS may be less strong than assumed above. It may be that other features in the clouds (such as the transition of different cloud types) might be playing a bigger role.

This assessment is obviously an important task for the authors of the IPCC AR6 report which is currently in it’s second-order draft. One (very modest) positive impact of the pandemic is that the deadline for papers to be accepted in order for them to be included in the final version of AR6 has been delayed to January 31st 2021, which will allow much of this new science to be published in time.

In the meantime, claims that climate sensitivity is much higher, or that worst cases scenarios need to be revised upwards, are premature.

  1. M.D. Zelinka, T.A. Myers, D.T. McCoy, S. Po‐Chedley, P.M. Caldwell, P. Ceppi, S.A. Klein, and K.E. Taylor, "Causes of Higher Climate Sensitivity in CMIP6 Models", Geophysical Research Letters, vol. 47, 2020.
  2. K.B. Tokarska, M.B. Stolpe, S. Sippel, E.M. Fischer, C.J. Smith, F. Lehner, and R. Knutti, "Past warming trend constrains future warming in CMIP6 models", Science Advances, vol. 6, pp. eaaz9549, 2020.
  3. F.J.M.M. Nijsse, P.M. Cox, and M.S. Williamson, "An emergent constraint on Transient Climate Response from simulated historical warming in CMIP6 models", 2020.
  4. K.D. Williams, A.J. Hewitt, and A. Bodas‐Salcedo, "Use of Short‐Range Forecasts to Evaluate Fast Physics Processes Relevant for Climate Sensitivity", Journal of Advances in Modeling Earth Systems, vol. 12, 2020.
Categories: Blogtastic

Forced responses: Jun 2020

Fri, 06/12/2020 - 04:08

Open thread on climate solutions. Please try and stay within a mile or two of the overall topic.

Categories: Blogtastic
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