Debra Saunders is a conservative columnist for the San Francisco Chronicle who has a history of writing misleading contrarian pieces on climate change. She contacted NASA Public Affairs recently for a comment on the initial glitch on the October GHCN numbers (see this earlier post for discussions of that). They forwarded the query to me and since her questions were straightforward, I answered them as best I could. Indeed in her subsequent column, she quotes me accurately and in context. However, the rest of her column shows none of the same appreciation for basic journalistic standards.
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Search Results for: consensus
Global dimming and global warming
Readers might remember a minor kerfuffle in EOS (the AGU house journal) in February this year in which Gerald Stanhill claimed to find a paradox in the contemporaneous effects of global warming and global dimming (a long term reduction of surface solar radiation, mainly due to aerosols and clouds). The article attracted attention mainly because the paradox was claimed to “pose [a challenge] to the consensus explanation of climate change”.
Rather than point out the subtle confusions (between surface and tropospheric forcing, and local and global signals) here, I and two co-authors wrote a comment to the journal. After a number of avoidable and unavoidable delays, this comment (along with another one and a reply) have all now appeared in EOS (Nov 6 edition). By now of course, the original piece has been long forgotten and so the point in having the correspondence printed is unclear, but still…
For those that care, I’ll link our comment once it’s been posted on the GISS website (now available here), but the bottom line is clearly seen in the following figure:
That is, if you take all of the IPCC AR4 models (now called the CMIP3 ensemble), then over the twentieth century all of them show varying degrees of global warming, while at the same time they show significant global dimming. An earlier paper of ours had pointed to the aerosols (unsurprisingly) being the dominant cause for long term changes in dimming, but that changes in clouds on a decadal basis were responsible for much of the shorter term variability. Thus there doesn’t appear to be much ‘paradox’ left to worry about – both dimming and warming are seen in models and in observations.
Apologies for appearing to push my own papers here (not something we like to do particularly), but the published comment would have been better done as a blog post in February. There may be a lesson there….
Climate Oscillations and the Global Warming Faux Pause
No, climate change is not experiencing a hiatus. No, there is not currently a “pause” in global warming.
Despite widespread such claims in contrarian circles, human-caused warming of the globe proceeds unabated. Indeed, the most recent year (2014) was likely the warmest year on record.
It is true that Earth’s surface warmed a bit less than models predicted it to over the past decade-and-a-half or so. This doesn’t mean that the models are flawed. Instead, it points to a discrepancy that likely arose from a combination of three main factors (see the discussion my piece last year in Scientific American). These factors include the likely underestimation of the actual warming that has occurred, due to gaps in the observational data. Secondly, scientists have failed to include in model simulations some natural factors (low-level but persistent volcanic eruptions and a small dip in solar output) that had a slight cooling influence on Earth’s climate. Finally, there is the possibility that internal, natural oscillations in temperature may have masked some surface warming in recent decades, much as an outbreak of Arctic air can mask the seasonal warming of spring during a late season cold snap. One could call it a global warming “speed bump”. In fact, I have.
Some have argued that these oscillations contributed substantially to the warming of the globe in recent decades. In an article my colleagues Byron Steinman, Sonya Miller and I have in the latest issue of Science magazine, we show that internal climate variability instead partially offset global warming.
We focused on the Northern Hemisphere and the role played by two climate oscillations known as the Atlantic Multidecadal Oscillation or “AMO” (a term I coined back in 2000, as recounted in my book The Hockey Stick and the Climate Wars) and the so-called Pacific Decadal Oscillation or “PDO” (we a use a slightly different term–Pacific Multidecadal Oscillation or “PMO” to refer to the longer-term features of this apparent oscillation). The oscillation in Northern Hemisphere average temperatures (which we term the Northern Hemisphere Multidecadal Oscillation or “NMO”) is found to result from a combination of the AMO and PMO.
In numerous previous studies, these oscillations have been linked to everything from global warming, to drought in the Sahel region of Africa, to increased Atlantic hurricane activity. In our article, we show that the methods used in most if not all of these previous studies have been flawed. They fail to give the correct answer when applied to a situation (a climate model simulation) where the true answer is known.
We propose and test an alternative method for identifying these oscillations, which makes use of the climate simulations used in the most recent IPCC report (the so-called “CMIP5” simulations). These simulations are used to estimate the component of temperature changes due to increasing greenhouse gas concentrations and other human impacts plus the effects of volcanic eruptions and observed changes in solar output. When all those influences are removed, the only thing remaining should be internal oscillations. We show that our method gives the correct answer when tested with climate model simulations.
Estimated history of the “AMO” (blue), the “PMO (green) and the “NMO” (black). Uncertainties are indicated by shading. Note how the AMO (blue) has reached a shallow peak recently, while the PMO is plummeting quite dramatically. The latter accounts for the precipitous recent drop in the NMO.
Applying our method to the actual climate observations (see figure above) we find that the NMO is currently trending downward. In other words, the internal oscillatory component is currently offsetting some of the Northern Hemisphere warming that we would otherwise be experiencing. This finding expands upon our previous work coming to a similar conclusion, but in the current study we better pinpoint the source of the downturn. The much-vaunted AMO appears to have made relatively little contribution to large-scale temperature changes over the past couple decades. Its amplitude has been small, and it is currently relatively flat, approaching the crest of a very shallow upward peak. That contrasts with the PMO, which is trending sharply downward. It is that decline in the PMO (which is tied to the predominance of cold La Niña-like conditions in the tropical Pacific over the past decade) that appears responsible for the declining NMO, i.e. the slowdown in warming or “faux pause” as some have termed it.
Our conclusion that natural cooling in the Pacific is a principal contributor to the recent slowdown in large-scale warming is consistent with some other recent studies, including a study I commented on previously showing that stronger-than-normal winds in the tropical Pacific during the past decade have lead to increased upwelling of cold deep water in the eastern equatorial Pacific. Other work by Kevin Trenberth and John Fasullo of the National Center for Atmospheric Research (NCAR) shows that the there has been increased sub-surface heat burial in the Pacific ocean over this time frame, while yet another study by James Risbey and colleagues demonstrates that model simulations that most closely follow the observed sequence of El Niño and La Niña events over the past decade tend to reproduce the warming slowdown.
It is possible that the downturn in the PMO itself reflects a “dynamical response” of the climate to global warming. Indeed, I have suggested this possibility before. But the state-of-the-art climate model simulations analyzed in our current study suggest that this phenomenon is a manifestation of purely random, internal oscillations in the climate system.
This finding has potential ramifications for the climate changes we will see in the decades ahead. As we note in the last line of our article,
Given the pattern of past historical variation, this trend will likely reverse with internal variability, instead adding to anthropogenic warming in the coming decades.
That is perhaps the most worrying implication of our study, for it implies that the “false pause” may simply have been a cause for false complacency, when it comes to averting dangerous climate change.
How to be a real sceptic
Scepticism is often discussed in connection with climate change, although the concept is often abused. I therefore thought it might be interesting to go back and see what the epitome of 20th Century sceptics, Bertrand Russell, had to say on the subject. This is extracted from the Introduction to his ‘Sceptical Essays’ (1928):
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BBC contrarian top 10
There is an interesting, if predictable, piece up on the BBC website devoted to investigating whether there is any ‘consensus’ among the various contrarians on why climate change isn’t happening (or if it is, it isn’t caused by human activity or if it is why it won’t be important, or if it is important, why nothing can be done etc.). Bottom line? The only thing they appear to agree about is that nothing should be done, but they have a multitude of conflicting reasons why. Hmm…
The journalist, Richard Black, put together a top 10 list of sceptic arguments he gathered from emailing the 61 signers of a Canadian letter. While these aren’t any different in substance to the ones routinely debunked here (and here and here), this list comes with the imprimatur of Fred Singer – the godfather to the sceptic movement, and recent convert from the view that it’s been cooling since 1940 to the idea that global warming is now unstoppable. Thus these are the arguments (supposedly) that are the best that the contrarians have to put forward.
Alongside each of these talking points, is a counter-point from the mainstream (full disclosure, I helped Richard edit some of those). In truth though, I was a little disappointed at how lame their ‘top 10’ arguments were. In order, they are: false, a cherry pick, a red herring, false, false, false, a red herring, a red herring, false and a strawman. They even used the ‘grapes grew in medieval England’ meme that you’d think they’d have abandoned already given that more grapes are grown in England now than ever before (see here). Another commonplace untruth is the claim that water vapour is ‘98% of the greenhouse effect’ – it’s just not.
So why do the contrarians still use arguments that are blatantly false? I think the most obvious reason is that they are simply not interested (as a whole) in providing a coherent counter story. If science has one overriding principle, it is that you should adjust your thinking in the light of new information and discoveries – the contrarians continued use of old, tired and discredited arguments demonstrates their divorce from the scientific process more clearly than any densely argued rebuttal.
If You See Something, Say Something
Gavin provided a thoughtful commentary about the role of scientists as advocates in his RealClimate piece a few weeks ago.
I have weighed in with my own views on the matter in my op-ed today in this Sunday’s New York Times. And, as with Gavin, my own views have been greatly influenced and shaped by our sadly departed friend and colleague, Stephen Schneider. Those who were familiar with Steve will recognize his spirit and legacy in my commentary. A few excerpts are provided below:
The Sheep Albedo Feedback
) 
The already-reeling "consensus" supposedly linking climate change to CO2 is about to receive its final coup-de-grace from a remarkable new result announced in a press conference today by Dr. Ewe Noh-Watt of the New Zealand Institute of Veterinary Climatology [1]. Noh-Watt and his co-workers, describing work funded by a generous grant from the Veterinary Climate Science Coalition, declared "We have seen the future of climate — and it is Sheep." Prof. Jean-Belliere Poisson d’Avril, star student of Claude Allegro Molto-Troppo (discoverer of the Tropposphere) reacted with the words, "Parbleu! C’est la meilleure chose depuis les baguettes tranchées!"
The hypothesis begins with the simple observation that most sheep are white, and therefore have a higher albedo than the land on which they typically graze (see figure below). This effect is confirmed by the recent Sheep Radiation Budget Experiment. The next step in the chain of logic is to note that the sheep population of New Zealand has plummeted in recent years. The resulting decrease in albedo leads to an increase in absorbed Solar radiation, thus warming the planet. The Sheep Albedo hypothesis draws some inspiration from the earlier work of Squeak and Diddlesworth [2] on the effect of the ptarmigan population on the energy balance of the Laurentide ice sheet. Noh-Watt hastens to emphasize that the two hypotheses are quite distinct, since the species of ptarmigan involved in the Squeak-Diddlesworth effect is now extinct.
Friday round-up
Blogging has been a little light recently (apologies!), but here are a few pieces that have caught our eye this week.
First up, the Columbia Journalism Review has a two–parter on journalistic coverage of climate change inspired by comments from Jeff Huggins on the Andy Revkin’s Dot Earth blog. The key issues CJR addresses are familiar ones to readers here: how to communicate mainstream science in a way that doesn’t distort the reality of the consensus on many issues in favour of controversy on more cutting-edge topics. Definitely worth a read, and proof (if such were needed) that commenting on blogs can make a difference to coverage.
Next, the role of CO2 as a long-term climate forcing. The old CO2 lead/lag issue keeps making the rounds as a contrarian talking point (and made a brief resurgence here in comments this week) despite the fact that the existence of impact of climate on the carbon cycle in no way invalidates the impact of CO2 (as a greenhouse gas) on climate. However, there is a nice paper in Nature this week (Lunt et al, 2008) which looks at the various proposed triggers for the onset of the quaternary glaciations at the end of the Pliocene (~3 million years ago). These triggers involve, permanent El Nino events, the closing of the Isthmus of Panama, changes in orbital forcing, tectonic uplift of the Rocky mountains – and long-term decreases in CO2 as a function of very slow variations in sea floor spreading and chemical weathering. Lunt et al find that only the change in CO2 (400 ppm to 280 ppm) can explain the changes in the ice sheet. None of the other ideas come even close.
Thus, it looks very much like the climate changed radically due to this externally forced drift in CO2 (and tectonic is external for climate purposes on this timescale). As a corollary, this is an expansion of the idea we discussed a few months back, that the long term changes in the Earth system due to external forcings might be well be larger than the classical (Charney) sensitivity we often talk about.
Third. There has been a lot of discussion on energy futures in the comments – Nature had a good rundown of the scientific constraints on the different prospects. But this video is a quite entertaining discussion of why we just can’t get our heads around the issue from Dan Gilbert (h/t GH).
Finally, a commentary on the prospects for continued employment as an Arctic ice expert (h/t Climate Feedback).
Copernicus and Arrhenius: Physics Then and Physics Today
There was a really interesting article in Physics Today this past October on the parallels between the slow acceptance of the idea of anthropogenic climate change and of the idea that the earth circles the sun.
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WSJ Editorial Board: Head Still Buried in the Sand
) While the rest of the world has basically accepted the conclusion of the latest IPCC report, one small village still holds out against the tide – the Wall Street Journal editorial board. This contrasts sharply with the news section of the paper which is actually pretty good. They had a front-page piece on business responses to global warming issues which not only pointed out that business was taking an interest in carbon reduction, but the article more or less took as a given that the problem was real. However, as we have pointed out before, the editorial pages operate in a universe all their own.
This would not be of much concern if the WSJ wasn’t such an influential paper in the US. However, the extent of its isolation on this issue is evident from the amusing reliance on the error-prone Christopher Monckton. They quote him saying that the sea level rise predictions were much smaller than in IPCC TAR (no they weren’t), that the human contribution to recent changes has been ‘cut by a third’ (no it hasn’t), and that the Summary for Policy Makers (SPM) was written by politicians (no it wasn’t – the clue is in the name).
Even more wrong is the claim that “the upcoming report is also missing any reference to the infamous ‘hockey stick’ “. Not only are the three original “hockey stick” reconstructions from the IPCC (2001) report shown in the (draft) paleoclimate chapter of the new report, but they are now joined by 9 others. Which is why the SPM comes to the even stronger conclusion that recent large-scale warmth is likely to be anomalous in the context of at least the past 1300 years, and not just the past 1000 years.
Thus on any index of wrongness, this WSJ editorial scores pretty high. What puzzles us is why their readership, who presumably want to know about issues that might affect their bottom line, tolerate this rather feeble denialism. While we enjoy pointing out their obvious absurdities, their readers would probably be better off if the WSJ accepted Jeffery Sachs’ challenge. For if they can’t be trusted to get even the basic checkable facts right on this issue, why should any of their opinions be taken seriously?