Today, Science published an important comment pointing out that there were serious errors in a climate research article that it published in October 2004. The article concerned (Von Storch et al. 2004) was no ordinary paper: it has gone through a most unusual career. Not only did it make many newspaper headlines [New Research Questions Uniqueness of Recent Warming, Past Climate Change Questioned etc.] when it first appeared, it also was raised in the US Senate as a reason for the US not to join the global climate protection efforts. It furthermore formed a part of the basis for the highly controversial enquiry by a Congressional committee into the work of scientists, which elicited sharp protests last year by the AAAS, the National Academy, the EGU and other organisations. It now turns out that the main results of the paper were simply wrong.
[Read more…] about A Mistake with Repercussions
Climate modelling
How not to write a press release
A recent BBC radio documentary on the possible over-selling of climate change, focussed on the link between high profile papers appearing in Nature or Science, the press releases and the subsequent press coverage. One of the examples chosen was the Stainforth et al climateprediction.net paper that reported the ranges of climate sensitivity within their super-ensemble of perturbed physics runs. While there was a lot of interesting science in this paper (the new methodology, the range of results etc.) which fully justified its appearance in Nature, we were quite critical of their basic conclusion – that climate sensitivities significantly higher than the standard range (1.5 – 4.5ºC) were plausible – because there is significant other data, predominantly from paleo-climate, that pretty much rule those high numbers out (as we discussed again recently). The press coverage of the paper mostly picked up on the very high end sensitivities (up to 11ºC) and often confused the notion of an equilibirum sensitivity with an actual prediction for 2100 and this lead to some pretty way-out headlines. I think all involved would agree that this was not a big step forward in the public understanding of science.
Why did this happen? Is it because the scientists were being ‘alarmist’, or was it more related to a certain naivety in how public relations and the media work? And more importantly, what can scientists do to help ensure that media coverage is a fair reflection of their work? [Read more…] about How not to write a press release
How much future sea level rise? More evidence from models and ice sheet observations.
Lots of press has been devoted to four papers in this week’s Science, on the topic of ice sheets and sea level.
We’ve already discussed the new evidence that Greenland’s glaciers are speeding up. What is new this week is an effort to evaluate the impact of future warming on Greenland by looking at what happened to it last time it got very warm — namely during the Last InterGlacial (LIG) period, about 125,000 years ago. The same group of authors looked at this in two ways, using NCAR’s Community Climate System model (CCSM) coupled to a state-of-the-art 3-D ice sheet model.
[Read more…] about How much future sea level rise? More evidence from models and ice sheet observations.
Climate sensitivity: Plus ça change…
Almost 30 years ago, Jule Charney made the first modern estimate of the range of climate sensitivity to a doubling of CO2. He took the average from two climate models (2ºC from Suki Manabe at GFDL, 4ºC from Jim Hansen at GISS) to get a mean of 3ºC, added half a degree on either side for the error and produced the canonical 1.5-4.5ºC range which survived unscathed even up to the IPCC TAR (2001) report. Admittedly, this was not the most sophisticated calculation ever, but individual analyses based on various approaches have not generally been able to improve substantially on this rough estimate, and indeed, have often suggested that quite high numbers (>6ºC) were difficult to completely rule out. However, a new paper in GRL this week by Annan and Hargreaves combines a number of these independent estimates to come up with the strong statement that the most likely value is about 2.9ºC with a 95% probability that the value is less than 4.5ºC. [Read more…] about Climate sensitivity: Plus ça change…
Richard Lindzen’s HoL testimony
Prof. Richard Lindzen (MIT) is often described as the most respectable of the climate ‘sceptics’ and is frequently cited in discussions here and elsewhere. Lindzen clearly has many fundamentally important papers under his belt (work on the QBO and basic atmospheric dynamics), and a number of papers that have been much less well received by the community (the ‘Iris’ effect etc.). Last year, he gave evidence to and answered questions from, a UK House of Lords Committee investigating the economics of climate change, in which he discoursed freely on the science. I’ll try here to sort out what he said. [Read more…] about Richard Lindzen’s HoL testimony
Polar Amplification
Guest commentary by Cecilia Bitz, University of Washington
“Polar amplification” usually refers to greater climate change near the pole compared to the rest of the hemisphere or globe in response to a change in global climate forcing, such as the concentration of greenhouse gases (GHGs) or solar output (see e.g. Moritz et al 2002). Polar amplification is thought to result primarily from positive feedbacks from the retreat of ice and snow. There are a host of other lesser reasons that are associated with the atmospheric temperature profile at the poles, temperature dependence of global feedbacks, moisture transport, etc. Observations and models indicate that the equilibrium temperature change poleward of 70N or 70S can be a factor of two or more greater than the global average. [Read more…] about Polar Amplification
Naturally trendy?
From time to time, there is discussion about whether the recent warming trend is due just to chance. We have heard arguments that so-called ‘random walk‘ can produce similar hikes in temperature (any reason why the global mean temperature should behave like the displacement of a molecule in Brownian motion?). The latest in this category of discussions was provided by Cohn and Lins (2005), who in essence pitch statistics against physics. They observe that tests for trends are sensitive to the expectations, or the choice of the null-hypothesis .
Busy Week for Water Vapor
It’s been a busy week for water vapor, and I have two recent papers to discuss. The first is the paper "Anthropogenic greenhouse forcing and strong water vapor feedback increase temperature in Europe" by Rolf Philipona et al. (GRL, 2005, subscription required for full text), which has attracted a certain amount of media attention. The overall goal of the paper is to understand, from a physical standpoint, why European temperatures have been increasing three times faster than the Northern Hemisphere average. It focuses on the changes between 1995 and 2002, over which time good surface radiation budget observations are available. The paper reports some results on the role of large scale circulation changes (which they conclude are minor) but I’ll concentrate on the results relating to water vapor.
Chaos and Climate
By James Annan and William Connolley
In this post, we will try to explain a little about chaos theory, and its relevance to our attempts to understand and forecast the climate system. The chaotic nature of atmospheric solutions of the Navier-Stokes equations for fluid flow has great impact on weather forecasting (which we discuss first), but the evidence suggests that it has much less importance for climate prediction.
Modeller vs. modeller
We recently got a request from Tom Cole, a water quality researcher, to explain some of the issues in climate modelling seen from his perspective as a fellow numerical modeller. His (slightly paraphrased) questions are the basis for this post, and hopefully the answers may provide some enlightment for modellers and non-modellers alike! [Read more…] about Modeller vs. modeller