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Is Pine Island Glacier the Weak Underbelly of the West Antarctic Ice Sheet?

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Guest post by Mauri Pelto

AntarcMapPeltoIt is popularly understood that glaciologists consider West Antarctica the biggest source of uncertainty in sea level projections. The base of the 3000-m thick West Antarctic Ice Sheet (WAIS) – unlike the much larger East Antarctic Ice Sheet – lies below sea level, and it has been recognized for a long time that this means it has the potential to change very rapidly. Most of the grounded West Antarctic ice sheet drains into the floating Ross and Ronne-Filchner ice shelves, but a significant fraction also drains into the much smaller Pine Island Glacier. Glaciologists are paying very close attention to Pine Island Glacier (“PIG” on map, right) and nearby Thwaites Glacier. In the following guest post, Mauri Pelto explains why.
[Read more…] about Is Pine Island Glacier the Weak Underbelly of the West Antarctic Ice Sheet?

Putting the recent Antarctic snowmelt minimum into context

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Guest Commentary by Andrew Monaghan and Marco Tedesco

Our study published in mid October in Geophysical Research Letters (Tedesco and Monaghan, 2009) documents record minimum snowmelt for Antarctica during austral summer 2008-2009 and lower-than-normal melt for several recent years, based on a 30-year satellite microwave record. Numerous blogs have cited the results as a challenge to previous studies reporting Antarctic warming, while also steadfastly ignoring other studies with similar results (e.g. Barrett et al., 2009). They have overlooked that these studies show that Antarctic warming has occurred mostly in winter and spring, whereas melting of course occurs in summer. And they oversimplify the causality and hence confuse our prediction for the future. We found that the same mechanism that has primarily caused low snowmelt in recent years will likely change in a manner that will enhance snowmelt in forthcoming decades. A brief summary follows. [Read more…] about Putting the recent Antarctic snowmelt minimum into context

On overfitting

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I don’t tend to read other blogs much, despite contributing to RealClimate. And I’m especially uninterested in spending time reading blogs full of ad hominem attacks. But a handful of colleagues apparently do read this stuff, and have encouraged me to take a look at the latest commentaries on our Antarctic temperature story. Since I happen to be teaching about principal component analysis to my graduate students this week, I thought it would be worthwhile to put up a pedagogical post on the subject. (If you don’t know what principal component analysis (PCA) is, take a look at our earlier post, Dummy’s Guide to the Hockey Stick Controversy).
[Read more…] about On overfitting

Breaking the silence about Spring

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Did you know that in 1965 the U.S. Department of Agriculture planted a particular variety of lilac in more than seventy locations around the U.S. Northeast, to detect the onset of spring — in turn to be used to determine the appropriate timing of corn planting and the like? The records the USDA have kept show that those same lilacs are blooming as much as two weeks earlier than they did in 1965. April has, in a very real sense, become May. This is one of the interesting facts that you’ll read about in Amy Seidl’s book, Early Spring, a hot-off-the-press essay about the impacts of climate change on the world immediately around us – the forest, the birds, the butterflies in our backyards.
[Read more…] about Breaking the silence about Spring

State of Antarctica: red or blue?

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Translations: (Italian)

A couple of us (Eric and Mike) are co-authors on a paper coming out in Nature this week (Jan. 22, 09). We have already seen misleading interpretations of our results in the popular press and the blogosphere, and so we thought we would nip such speculation in the bud.

The paper shows that Antarctica has been warming for the last 50 years, and that it has been warming especially in West Antarctica (see the figure). The results are based on a statistical blending of satellite data and temperature data from weather stations. The results don’t depend on the statistics alone. They are backed up by independent data from automatic weather stations, as shown in our paper as well as in updated work by Bromwich, Monaghan and others (see their AGU abstract, here), whose earlier work in JGR was taken as contradicting ours. There is also a paper in press in Climate Dynamics (Goosse et al.) that uses a GCM with data assimilation (and without the satellite data we use) and gets the same result. Furthermore, speculation that our results somehow simply reflect changes in the near-surface inversion is ruled out by completely independent results showing that significant warming in West Antarctica extends well into the troposphere. And finally, our results have already been validated by borehole thermometery — a completely independent method — at at least one site in West Antarctica (Barrett et al. report the same rate of warming as we do, but going back to 1930 rather than 1957; see the paper in press in GRL).

[Read more…] about State of Antarctica: red or blue?

The Younger Dryas comet-impact hypothesis: gem of an idea or fool’s gold?

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There was a paper in Science last week that has gotten quite a bit of press. It reports further evidence in support of the idea that the Younger Dryas — a distinct period towards the end of the last ice age when the deglaciation in the Northern Hemisphere was interrupted for a period of about 1300 years — was caused by a barrage of comets hitting North America.

When the first papers on this came out last year, we expressed skepticism. We remain skeptical and our reasons remain unchanged. But we think it is worth saying a bit more on this, because the reporting on this issue has largely ignored just how big an idea this is, and therefore how much more work would need to be done before it could be taken very seriously.
[Read more…] about The Younger Dryas comet-impact hypothesis: gem of an idea or fool’s gold?

Environmental reporters ought to be more responsible too

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At RealClimate, we have more than once been accused of being imbalanced — criticizing those who would deny the basic science of climate change, while leaving inflammatory statements by what might be called the “environmentalist side” without comment. It’s not an entirely a fair criticism, because there is a world of difference between the willful obfuscation of science and the naive exaggeration of it. There are however plenty of silly, and sometimes outrageous, claims made – see e.g. the Telegraph on Jan. 3rd — and we probably ought to do a better job of calling these out, particularly when they show up in prominent places. So to inaugurate the New Year, I humbly offer a rant about a minor but illustrative example that I happened to notice because there was a link to it on Nature Reports Climate Change.

The subject of the linked article, in the British online newspaper The Independent, is the decline of various bird and butterfly species in England. The article, entitled Changing climate devastates UK species, reports that “insects in particular, and creatures that feed on insects…were sharply reduced in numbers” due to a “cold late spring, a wet summer, with few sunny days, and the long dry autumn….” Now I have no reason to doubt the accuracy of the claim that 2008 was a hard year for UK insects and insectivores. But this is weather we’re talking about, not climate. And while it is true that at least one prominent study shows that there has been an overall increase in rainfall in the latitude band that includes the UK, and that climate models reproduce this trend (see e.g. the Zhang et al. article in Nature, in 2007), one cannot, as we are fond of pointing out, attribute a single, or even several individual extreme weather events to “climate change”.

Indeed, Peter Stott, a co-author on the Zhang et al. study noted, in reference to 2007 (the wettest summer on record in the UK) that “This latest study cannot make the link between climate change and what we have experienced so far this summer.” Moreover, most projections actually suggest drier summers in the UK in the future, though with increased convection (so less total precipitation, but bigger rainstorms).

Another thing that bugs me about the Independent article is the suggestion that climate is becoming “more unpredictable”. I suspect what is meant here is that we used to know what a mean season and normal variations were, and now we don’t. That’s valid, since the baseline climate is changing. But saying it this way — that “climate is becoming more unpredictable” is misleading. In fact, climate may, if anything, become more predictable as anthropogenic forcing becomes even more dominant (as greenhouse gas concentrations increase), relative to natural forcing and variability. And what is definitely not the case — but might be inferred from the article — is that weather is becoming more unpredictable. Weather prediction is based on observations just a few days in advance — climate and climate trends have nothing to do with it.

The point here is not that we shouldn’t be concerned about the fate of insects and birds in the UK (that would be the kind of conclusion that only the most willfully ignorant would draw.) They have been in decline for a long time (mostly due to land use change and pesticides) and there is little doubt that climate change will continue to add insult to injury. But it is simply wrong to confuse a year or even two years of unfavorable weather with a change in climate, and it is irresponsible to headline an article that is really about weather with the provocative juxtaposition of “climate” and “devastates”. Doing so gives the average reader the sense that their personal observations about “weird weather patterns” or fewer sightings of Parus caeruleus represent definitive manifestations of climate change. The fact is, climate changes are — so far — small enough in most places, relative to the natural variability, that one’s personal experience is a very poor guide to what is happening over the long term (observations of sea ice changes by those that live in the high Arctic notwithstanding).

Greenspan, Einstein and Reich

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Translations: (Italian) (Français)

shrekI often receive letters that range from amusing claims that we are overlooking changes in the magnetic field, to tales about how the “weight” of carbon dioxide keeps it “near the ground”. If the writer sounds serious, then I treat them seriously, and do my best to provide a helpful reply. Often, though, I find myself in a pointless debate of the most basic, well-established physical principles. I generally cut off the discussion at this point, because I simply don’t have the time. This can result in a hostile response accusing me of “having an agenda”. Most would call me naïve for bothering to respond in the first place.

But it is possible, after all, that somewhere in that barrage of letters lies a brilliant idea that ought to be heard, and could change the course of scientific history. How to tell the difference? Well, there is a story that we tell in our family that might provide some perspective on this.

[Read more…] about Greenspan, Einstein and Reich

Field notes from a Nature Conservancy meeting

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I had the opportunity to attend a three-day meeting of the Nature Conservancy last week in Vancouver. I was there with my RealClimate hat on, to offer ideas and insight on blogging in particular, and public communication of science in general.

While at the conference, I had a rare chance to see some of the inner workings of one of the world’s largest and most successful environmental organizations (this was an invite-only conference, and only a handful of us were other than Nature Conservancy staff and trustees). The Nature Conservancy has a reputation of being very non-partisan, and this was abundantly evident at the conference: There were representatives present from the Shell Oil Company, from the Christian Coalition, from Environmental Defense. This broad level of buy-in of Nature Conservancy goals is perhaps not surprising, given that the main thing this organization is known for is its method of protecting land: buying it. Neither free-market boosters (if there are there any remaining) nor lefty environmentalists have any trouble with this.

What was news to me, though, was the extent to which the Nature Conservancy is also working towards influencing policy on climate change. Getting serious about climate policy is no longer a partisan issue in the U.S.: both John McCain and Barak Obama are on record for supporting cap and trade carbon markets. But one might well ask what climate policy has to do with the buy-the-land-to-protect it method of the Nature Conservancy. As I learned at the conference, there are two rationales.

First, the Nature Conservancy has a strongly science-based policy for making land-purchasing decisions. They take into account things like the minimum viable ecosystem size in determining which acquisitions will actually have lasting impact. Trouble is, for many areas, the conditions those decisions are based on may change. Areas near sea level are an obvious example. But so are the more than 10,000 acres of native tallgrass prairie that they have protected in Kansas. How much will that ecosystem change with the projected changes in precipitation in this region? Obviously, the Nature Conservancy is taking into account such projections, as best they can. But they have also decided that the risks of climate change to the world’s ecosystems are too large to simply adapt to: hence their interest in helping to push governments to enact policies that will help mitigate it.

Second, it turns out that the Nature Conservancy’s mission is — and has always been — much broader than is widely recognized. As they note on their mission statement page they can’t possibly buy all the places they want to protect. To achieve their mission — “to preserve the plants, animals and natural communities that represent the diversity of life on Earth by protecting the lands and waters they need to survive” — they will clearly have to do something much bigger. The buzzword here is sustainability, and the nature Conservancy is now launching what they call their Campaign for a Sustainable Planet. This means a serious focus not just on direct ecosystem protection but also on sustainable development. International sustainable development goals, of course, are impossible to separate from international energy policy. And one cannot today talk about energy policy without talking about climate policy. It is therefore quite logical for the Nature Conservancy to be drawn into weighing-in on climate policy.

Now, what does this have to do with RealClimate? Well, the Nature Conservancy is interested in expanding their web-based communication toolbox. They already have a great deal of information on their web page: see for example their article on climate change adaptation, here; but they’d like to do more. And in particular, they are interested in getting more information out there from their scientists. As I already pointed out, The Nature Conservancy — which has over 700 full time scientists working for it — prides itself on being strongly science-based. So do we here at RealClimate (read our welcome page). Unlike us, whose day jobs are to produce and broadly disseminate scientific results (through teaching and publication), Nature Conservancy scientists don’t necessarily publish their work. There is no doubt a lot of really interesting and important work being done that doesn’t get out to many other scientists, let alone the general public. A blog, or something like it, could provide those scientists with a place to talk about their work. Hence my attendance at the meeting, to offer a bit of advice and perspective.*

Here at RealClimate, we look forward to seeing where Nature Conservancy goes with this, and wish them best success in their efforts. [Watch this space for an announcement, if and when they launch something.] For my part, I’ll be especially enthusiastic if the Nature Conservancy doesn’t limit itself to talking about its various projects around the world (interesting as those may be). What I’d really like to see is a site that provides their perspective on some of the more difficult — but really important — questions in the area of climate change impacts. How much danger are polar bears in, really? How will agriculture in Asian monsoon regions be affected? What are the broader effects of ocean acidification (beyond the immediate impact on coral reefs)? The Nature Conservancy won’t be the last word on this — any more than RealClimate is. But their perspective, from field scientists “on the ground”, could prove extremely valuable.

One additional thought. In several of the sessions I attended at the Nature Conservancy meeting, reference was made to the need to stabilize global temperature rise at no more than 2°C, and correspondingly to stabilize CO2 levels at no greater than 450 ppm (strictly speaking, this should be 450 ppm CO2-radiative-equivalent; there is a big difference, and it is often neglected). In each case, reference was made to the IPCC reports as the source of these numbers. Yet these numbers really don’t derive from the IPCC, which (rightly) shied away from being policy prescriptive. Rather, they have their origin in a small number of documents, notably the 1995 report of the German Advisory Council on Global Change, papers related to the Exeter conference on “avoiding dangerous climate change” and in European Union Council decisions (see the 1996 and 2006 Presidency Conclusions here). Clearly, the 2°C/450 ppm numbers have completely permeated the policy-advocacy realm. Yet while they are arguably derivable from the IPCC reports, it is actually not clear to what extent the larger scientific community really believes these are the right numbers. There simply has not been a process to evaluate this that compares in depth and breadth with the IPCC. A new and much more comprehensive analysis, by a much greater group of scientists, would be valuable at this juncture. Scientists are fond of saying that they cannot summarize their projections with a small handful of simple numbers, but simple numbers are what are being discussed in policy circles. If the “right” numbers are really so low as Jim Hansen believes (see our post on this, here), then the Nature Conservancy has an even more difficult task ahead.

*[For those interested in slogging through it, there’s a video of our session, here. It’s not just about me. There is also some really interesting stuff from Nature Conservancy staffer Jonathon Colman and from the folks who started the conservation clearinghouse and collaboration websites www.conservationyellowpages.org and wiserearth.org, as well as a demonstration (not altogether successful) of the emerging virtual reality conferencing technology which (when it works) might help all of us travel to conferences less often. A word of advice: skip all this and instead take a look at the Keynote lectures, by far better orators than me: Mark Tercek, Nature Conservancy CEO, Jerome Ringo, Apollo Alliance President, and CARE C.O.O. Steve Hollingworth

On straw men and Greenland: Tad Pfeffer Responds

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In a recent post about sea level rise, we highlighted a paper by the University of Colorado’s Tad Pfeffer and others in which they show that one can rule out more than 2 meters of sea level rise in the next century. While we liked the paper very much, we also complained that Pfeffer and colleagues had created a bit of a straw man, by implying that it had been seriously proposed that Greenland’s near term contribution to sea level rise could be much larger than that. In fact (we said), none of us in the climate science community ever took such ideas seriously, even if the popular press thought we did. Tad responds by pointing out that in fact there is published work attributing considerable likelihood to such extreme scenarios, and that there are numerous studies that at the very least strong imply it. He also reminded me that their paper actually rules out a contribution of more than about 50 cm from Greenland, significantly below some other recent published estimates. That makes their work even more important, since there are several publications that definitely consider upwards of one meter (from Greenland alone) by 2100 to be plausible. Pfeffer et al. conclude that that is simply not the case (at least in their informed view). Still, we remind readers that our chief complaint was that Pfeffer et al.’s work was taken by many in the media as a downward revision to sea level rise estimates, whereas in fact most informed estimates had put an upper limit well below that. See our earlier post on the IPCC Sea Level numbers.

In any case. Pfeffer et al’.s response to our post follows below. Fair enough.

A response to RealClimate’s post on our paper about sea level rise

W.T. Pfeffer, J.T. Harper, and S. O’Neel
15 September 2008

We have read with interest – and, we admit, surprise – the RealClimate post concerning our 5 September publication in Science entitled “Kinematic Constraints on 21st Century Sea Level Rise.” The source of our surprise, however, is probably not what the RealClimate authors imagine – we had fully expected a vigorous defense of very high rates of sea level rise (greater than 2 m/century), but not a denial that such rates had ever been hypothesized.

We do not state anywhere in our paper that 2m or more of SLR by 2100 has been published as a peer reviewed and “informed estimate”. We do state that this has been ‘inferred’ and ‘argued’ as a “viable 21st century scenario”. We believe there is value in constraining the upper limits to the role of ice dynamics in future SLR. And, from what we know about historical rates of SLR in conjunction with what ‘we know we don’t know’ about ice dynamics, we believe it is reasonable to ponder very high rates of SLR in the next century. However, we also believe that it is problematic to project such a ‘hypothesis’ as a supported theory without proper testing by the scientific method. The question raised by RC is whether or not this hypothesis has circulated within the scientific community.

In his 2007 paper (Environ. Res. Lett. 2(2007)) Hansen proposes a rate of sea level rise of “5 m this century.” This is hypothetical, but he is confident that it is a “far better estimate than a linear response”. This is accompanied by his statement that he finds it “almost inconceivable that BAU climate change would not yield a sea level change of the order of meters on the century timescale.” The provisional nature of his discussion is irrelevant; it is an explicit statement that 5 m of sea level rise in this century is a possibility he regards as viable, published in the scientific literature by the person who is arguably (and deservedly) the most visible and authoritative climate scientist in the world. No reader of this paper would assume that Hansen didn’t actually mean what he said. Hansen reinforced this idea in other publications and statements, including in his briefing to Congress on 23 June 2008 (“sea level rise of at least two meters is likely this century”). Our analysis specifically tested the likelihood of next-century sea level rise of more than 2 m, and Hansen explicitly hypothesized 5 m of sea level rise in this century.

Hansen has gone on record with specific numbers, but other published studies including the 2006 Overpeck and Otto-Bliesner Science papers left the upper limit open ended, and certainly implied it could be quite high. The fact that this idea was present in the scientific community was confirmed for us by 8 scientific presentations we gave on this topic in the past year (5 in the US, including the Fall 2007 AGU and 3 in Europe). At none of those talks did anyone in the audience question what high forecasts we were referring to. The comments we got back on our work were overwhelmingly positive, and were along the lines that what we had presented was a good next step – both to move past the IPCC’s low sea level forecasts, and as a response to the persistent hypotheses of very high rates of sea level rise that were circulating. Criticisms, where they were voiced, were largely that we were underestimating the power of dynamics and that rates of sea level rise well in excess of 2 m/century might occur in spite of our conclusions.

We agree that the media coverage of our paper (as well as others before it) has undesirable side effects. Wherever we had the opportunity we pressed media writers not to use terms like “exaggerated” or “high sea level forecasts debunked,” and we have consistently stressed that our results indicate a very significant sea level rise and are no justification for any kind of complacency. We have stressed that even our low end scenario of 0.8 m of SLR would have tremendous consequences. However, we stand by our statements that sea level rise at rates of substantially more than 2 m this century were in fact put forward as a likely possibility.

Earlier this summer Andy Revkin published a piece in the New York Times about what he has termed the “Whiplash Effect”: confusion created in the public mind by media coverage of rapidly evolving scientific ideas. There has certainly been some whiplash in this case. However it is others who cracked the whip. We have simply refused to let go of the other end.