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A phenomenological sequel

Filed under: — rasmus @ 27 November 2007


Does climate sensitivity depend on the cause of the change?
Can a response to a forcing wait and then bounce up after a period of inertness?
Does the existence of an 11-year time-scale prove the existence of solar forcing?
Why does the amplitude of the secular response drop when a long-term trend is added?
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Six Degrees

Filed under: — eric @ 25 November 2007

“Alarmism” is a term that gets bandied about a lot. It is often said that one should not call out “fire” in a crowded building. But it really depends, one might say, on whether the “calling out” is done in such a way as to simultaneously prevent a stampede and prevent anyone getting burned.

This riddle was very much on my mind as I sat down to write my thoughts on Mark Lynas’s book, Six Degrees: Our Future on a Hotter Planet (London: Fourth Estate, 2007). I don’t read much popular science literature, and I doubt I would have read this book if I hadn’t made the mistake of referring to it (in a negative manner) in the comments section of a RealClimate post. I don’t think my error was very grave. What I actually said was that if what I had heard about the book from the press materials were true, then the book was probably alarmist and not worth reading. But I don’t blame the author for asking me to read the book and see for myself. He said that the press (in this case Sunday Times (London)) had misconstrued what he says in the book, and he assured me that is was all based on very careful review of the scientific literature. I was thus both curious and obligated to read the book.

Mark Lynas will no doubt be pleased that I very much like the book. To be sure, it is alarming, but the question of whether it is alarmist is a more difficult one, and I don’t think the answer lies in debating the book. Rather, it lies in looking closely at the underlying science the book builds on. I don’t intend to do that here, but I do think that all climate scientists (particularly those that talk to the public) ought to read this book, and ask themselves a question. I’ll get to that question at the end, after saying a bit more about the book.

Six Degrees, as the title suggests, is comprised of six main chapters (plus an introduction and a conclusion). Each of the main chapters examine what the earth might look like as we raise the planet’s temperature by 1o, 2o, etc. degrees Celsius, based on what the scientific literature has to say about it. Laying out the book this way makes for a good logical progression of ideas, and a fair bit of suspense. Very few people, Lynas says, have got “the slightest idea what two, four or six degrees of average warming actually means in reality, and I’m sure he is right.

In Chapter 1, at 1o, we have predictions of, for example, an annually ice free Arctic ocean. Yes, quite plausible and supported by the literature, and perhaps occurring a little sooner than expected. At 2o, we have, “so whilst southern China can expect more flooding as the two-degree line is approached, the oceanic time lag means that it may take much longer for the rain-bearing summer monsoon to reach the drought-stricken north.” Yes, certainly plausible based on the studies Lynas cites. At 4o, we have “with global sea levels half a meter or more above current levels, [the Egyptian city of] Alexandria’s long lifespan will be drawing to a close. Even in today’s climate, a substantial part of the city lies below sea level, and by the latter part of this century a terminal inundation will have begun. … a rise in sea levels of 50 cm would displace 1.5 million people and cause $35 billion of damage.” Alarmist? Hardly. A 50 cm rise in sea level, is well within the conservative IPCC projections, even for temperature rises less than four degrees.

At 5o and 6o, the book really does start to sound alarmist, with the analogy to Dante’s Inferno – used to good literary effect throughout the book – coming very much to the fore. At five degrees, we have “an entirely new planet is coming into being – one largely unrecognizable from the Earth we know today. At six degrees, “… the pump is primed … not for flourishing palm trees in Alaska, but for the worst of all earthly outcomes: mass extinction.”

Aha, say the skeptics! It is alarmist after all. But is it? Lynas’s reference to the “entirely different planet” actually refers to the fact that at five degrees, the “remaining ice sheets are eventually eliminated from both poles.” That’s entirely true. And unlike in Gore’s discussion of sea level in Inconvenient Truth Lynas does emphasize the long timescales (thousands of years) in this case. Furthermore, there is published research that raises the likelihood of the significant loss of ice sheets at lower temperatures, and Lynas could have claimed certainty of a disappearing Greenland ice sheet in an earlier chapter. That he doesn’t do that is characteristic of the book: it doesn’t tend to go beyond the published literature. This is what Lynas claims at the outset — “all of the material in the book comes from the peer-reviewed scientific literature” – and I think he does an admirable job.

And that brings us back to the question I promised to raise at the beginning, which is this:

If a reading of the published scientific literature paints such a frightening picture of the future as Six Degrees suggests – even while it honestly represents that literature – then are we being too provocative in the way we write our scientific papers? Or are we being too cautious in the way we talk about the implications of the results?

Les Chevaliers de l’Ordre de la Terre Plate, Part I: Allègre and Courtillot

Filed under: — raypierre @ 18 November 2007 - (Français)

France has a per capita carbon emission of 1.64 tonnes, compared to 2.67 tonnes for the U.K and 5.61 tonnes for the US. So, if anybody has earned the right to rest on their laurels and pontificate to the rest of the developed world about what they should be doing, you’d think it would be France. Far from it, under the leadership of Nicolas Sarkozy, France has embarked on an ambitious program of deeper carbon reductions. In introducing the measures, Sarkozy said "The guiding principle is that the cost to the climate — the carbon cost — will be integrated into planning of all major public projects, and into all deliberations affecting the public." These measures include: a commitment that all new buildings would be net energy producers by 2020, incandescent lighting would be banned by 2010, buyers of efficient vehicles would be subsidized, drivers of inefficient vehicles would be penalized, and road construction would be severely curtailed in favor of expanded rail travel using state-of-the-art French TGV technology. A carbon tax is also being seriously contemplated. These proposals are the result of an intensive months-long series of discussions with scientists and stakeholders such as environmental nongovernmental organizations, industry representatives, and labor union representatives. The process, known as Le Grenelle de l’Environnement, was described here by Nature (subscription required) and a summary of some of Sarkozy’s proposed actions was reported in the press here.

All the same, there has been some pushback from a vocal pair of highly decorated French academicians, Claude Allègre being the most prominent and noisiest of the two. In recent years, Vincent Courtillot has emerged as a reliable sidekick to Allègre — a Dupont to his Dupond — helping to propagate Allègre’s claims and adding a few of his own. Both are members of the Académie des Sciences, and Allègre has been awarded both the Crafoord Prize and Bowie Medal. Allègre has an impressive list of publications relating to the Earth’s interior, and besides that was Minister for Education, Research and Technology in the Jospin government. Courtillot — currently director of the Institut de Physique du Globe de Paris (IPGP) — has had a distinguished record of research on fundamental aspects of geomagnetism and is currently President of the Geomagnetism and Paleomagnetism Section of the American Geophysical Union. Their views were amply (some would say more than amply) represented at a symposium on the IPCC report, held last Spring at the Academie (See the issue "Evolution des Climats" of La Lettre de l’Académie des sciences, and press reports in Le Figaro, Le Monde, and Liberation). What does all this mean? Are the opinions of Allègre and Courtillot founded on some special profound insight that has escaped the notice of the community of scientists who have devoted entire careers to studying climate? Let’s take a look.

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Global dimming and global warming

Filed under: — gavin @ 14 November 2007

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….

BBC contrarian top 10

Filed under: — gavin @ 13 November 2007

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.

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