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The missing piece at the Wegman hearing

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It’s not often that blogs come up in congressional hearings, but RealClimate was mentioned yesterday in the Energy and Commerce hearings on the ‘Hockey Stick’ affair. Of course, it was only to accuse us of being part of tight-knit social network of climate scientists, but still, the public recognition is nice.

There is much that could be said about the hearings (and no doubt will be) and many of the participants (Tom Karl, Tom Crowley, Hans von Storch, Gerry North) did a good job in articulating the big picture on climate change independently of the ‘hockey stick’ study as we’ve highlighted before. But it seems to us that there was a missing element in the discussions. That element was the direct implication of the critique that was the principal focus of Wegman’s testimony and that was mentioned periodically throughout the day. [Read more…] about The missing piece at the Wegman hearing

It’s different in Europe

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Paul Thacker has an interesting interview with a European and a US journalist on the media coverage of climate science in Europe. The standard contrarian line does not get as much attention there as it does in the US (which is good), but whether that means that the journalism there is actually better is a tricky point. So what makes for good climate science journalism and do they do it better over there?

Introducing RC forum

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It’s clear that there is a need to have some posts and discussions that specifically deal with up-to-the-minute articles and issues that we don’t necessarily want to cover in our usual detail. This might be related to a recent op-ed which just repeats the same talking-points as usual, or pointers to good discussions on other sites. To that end, we are introducing a separate category of post, called “RC forum”, where we will post these more minor items. Hopefully, this will help make interesting comment threads, which now sometimes occur under completely unrelated posts, easier to find and reference. The big pieces will still appear on the front page and in the RSS and Google feeds but the RC forum pieces will not. Right now, a notification email is sent out for every post, but we could restrict this to main page items if needed. There is now a link on the top bar to the RC Forum page and recent comments on Forum pieces will appear on the sidebar. Please let us know if you think this is a good idea or if you have ideas to improve it.

‘The Discovery of Global Warming’ update

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If you haven’t already seen the American Institute of Physics website by Spencer Weart on the ‘The Discovery of Global Warming’, we heartily recommend it. It provides both a summary of science, and more importantly, a history of how an obscure speculation from over one hundred years ago has become the scientific consensus of today. It has recently been updated with many more references from 1873 to the present, and so is even more worth reading. Spencer is very keen on getting feedback on the project, so don’t hesitate to let him know what you think.

Ice Sheets and Sea Level Rise: Model Failure is the Key Issue

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Guest post by Michael Oppenheimer, Princeton University

A plethora of research articles has appeared over the past year reporting new observations of the Greenland and West Antarctic ice sheets along with associated modeling results. RealClimate has reviewed the issues raised by these articles and attempted to clarify the sometimes conflicting inferences about the current mass balance of the ice sheets, as well as their future contributions to global mean sea level rise (see here and here).

Nevertheless, the issue still seems to perplex many journalists and others because there are two entirely distinct aspects of the sea level rise problem that are emphasized, depending on which scientists are speaking. On the one hand, these ices sheets are large enough to ultimately raise sea level by 7m and about 5m, for Greenland and West Antarctica, respectively. On the other, the recent observations that caused such a stir report a current contribution to the rate of sea level rise not exceeding ~1mm/yr from both ice sheets taken together. If this rate were maintained, the ice sheets would make a measurable but minor contribution to the global sea level rise from other sources, which has been 1-2mm/yr averaged over the past century and 3mm/yr for 1993-2003, and is projected to average 1-9mm/yr for the coming century (see IPCC Third Assessment Report).

The key question is whether the ice sheet contribution could accelerate substantially (e.g., by an order of magnitude) either in this century or subsequently. Sea levels were indeed much higher in the distant, warmer past but the timing of earlier sea level rise is very uncertain. From the point of view of societal and ecosystem adaptation, the timescale over which ice sheets might disintegrate, which may be on the order of centuries or millennia according to the two extremes posited in the literature, is crucial. [Read more…] about Ice Sheets and Sea Level Rise: Model Failure is the Key Issue

National Academies Synthesis Report

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The long-awaited NAS synthesis report on surface temperature reconstructions over the last few millennia is being released today. It’s a long (155 page) report and will take a while to digest, but we applaud the committee for having tried to master a dense thicket of publications and materials on the subject over a relatively short time.

It is probably expecting too much for one report might to put to rest all the outstanding issues in a still-developing field. And given the considerable length of the report, we have little doubt that keen contrarians will be able to mine the report for skeptical-sounding sentences and cherry-pick the findings. However, it is the big picture conclusions that have the most relevance for the lay public and policymakers, and it is re-assuring (and unsurprising) to see that the panel has found reason to support the key mainstream findings of past research, including points that we have highlighted previously:
[Read more…] about National Academies Synthesis Report

NOAA: Hurricane forecasts

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Guest commentary from Thomas Crowley

NOAA has issued its annual forecast for the hurricane season, along with its now-standard explanation that there is a natural cycle of multidecadal (40-60 year) length in the North Atlantic circulation (often referred to as the “Atlantic Multidecadal Oscillation”–see Figure), that is varying the frequency of Atlantic tropical cyclones, and that the present high level of activity is due to a concurrent positive peak in this oscillation. [Read more…] about NOAA: Hurricane forecasts

On a Weakening of the Walker Circulation

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by Ray Pierrehumbert and Rasmus Benestad

Second article of our 3-part series on atmospheric circulation and global warming

In Part I we outlined some general features of the tropical circulation, and discussed ways in which increases in anthropogenic greenhouse gases might affect El Niño. Now we take up the question of how global warming might affect the quasi-steady east-west overturning circulation known as the Walker Circulation. The Walker circulation affects convection and precipitation patterns, the easterly Trade Winds, oceanic upwelling and ocean biological productivity; hence, changes in this circulation can have far-reaching consequences. It also provides the background state against which El Niño events take place, and so changes in the Walker circulation should form an intrinsic part of thinking about how global warming will affect El Niño. In a paper that recently appeared in Nature, Vecchi, Soden, Wittenberg, Held, Leetmaa and Harrison present intriguing new results which suggest that there has already been a weakening of the Walker circulation in the past century, and that the observed changes are consistent with those expected as a response to increases in anthropogenic greenhouse gases. The discussion in Vecchi et al. also raises some very interesting issues regarding the way the hydrological cycle might change in a warming world.

[Read more…] about On a Weakening of the Walker Circulation

How Red are my Proxies?

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Guest commentary by David Ritson

Realclimate recently gave a detailed review of the issues surrounding the Von Storch et al. (2004) Science article that purported to show that the paleo-reconstructions of Mann et al. were invalid. Part of the review centered on a comment of Wahl, Amman and myself and the response to it by Von Storch et al that appeared on April 27 in Science. The response admitted that our critique of their original results was correct but then opened up a new area of debate. As in their original 2004 article von Storch et al had used a coupled climate model (AOGCM) to simulate the temperatures of the last two thousand years. They had then generated pseudo-proxies by adding noise at selected spatial locations to the AOGCM generated temperature histories. The added noise was purportedly designed to represent non-climatic effects such as disease or insect infestation. This simulated ‘noisy’ world then can be used as a test-bed for the reconstruction methodology. A given analysis procedure is validated if it successfully recovers the original AOGCM noise free results and could be rejected if it fails to recover the original results. Of course such testing only makes sense if the simulated test world has characteristics similar to the real-world. [Read more…] about How Red are my Proxies?

Thank you for emitting

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A recent movie, ‘Thank You for Smoking‘, amusingly highlighted the lengths that PR reps for the tobacco companies would go to distort the public discourse on the health effects of smoking. Lest you thought that was of merely historical relevance, we would like to draw your attention to two of the funniest videos around. Lifting a page straight out of the Nick Naylor playbook, the CEI (an industry-funded lobby group) has launched a new ad campaign that is supposed to counteract all those pesky scientific facts about global warming.

The first ad (both available here) deserves to become a classic of the genre. It contains the immortal lines ‘CO2: they call it pollution, we call it Life!’ – it is beyond parody and without content – and so you should definitely see it. The second ad has a little more substance – but is as misleading as you might expect.
[Read more…] about Thank you for emitting