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Archives for January 2012

The AR4 attribution statement

29 Jan 2012 by Gavin

Back in 2007, the IPCC AR4 SPM stated that:

“Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.”

This is a clear statement that I think is very well supported and correctly reflects the opinion of most climate scientists on the subject (and was re-affirmed in two recent papers (Jones and Stott, 2011;, Huber and Knutti, 2011)). It isn’t an isolated conclusion from a single study, but comes from an assessment of the changing patterns of surface and tropospheric warming, stratospheric cooling, ocean heat content changes, land-ocean contrasts, etc. that collectively demonstrate that there are detectable changes occurring which we can attempt to attribute to one or more physical causes.

Yet, in a paper just out in BAMS (Curry and Webster, 2011) this statement is apparently evidence that IPCC is unable to deal with uncertainty. Furthermore, Judith Curry has reiterated on her blog that the term ‘most’ is imprecise and undefined. For instance:

Apart from the undefined meaning of “most” in AR4 (which was subsequently clarified by the IPCC), the range 50.1-95% is rather imprecise in the context of attribution.

However, Curry’s argument is far from convincing, nor is it well formed (why is there a cap at 95%?). Nor was it convincing when I discussed the issue with her in the comments at Collide-a-Scape last year where she made similar points. Since the C&W paper basically repeats that argument (as has also been noticed by Gabi Hegerl et al who have a comment on the paper (Hegerl et al.)), it is perhaps worth addressing these specific issues again.
[Read more…] about The AR4 attribution statement

References

  1. G.S. Jones, and P.A. Stott, "Sensitivity of the attribution of near surface temperature warming to the choice of observational dataset", Geophysical Research Letters, vol. 38, pp. n/a-n/a, 2011. http://dx.doi.org/10.1029/2011GL049324
  2. M. Huber, and R. Knutti, "Anthropogenic and natural warming inferred from changes in Earth’s energy balance", Nature Geoscience, vol. 5, pp. 31-36, 2011. http://dx.doi.org/10.1038/ngeo1327
  3. J.A. Curry, and P.J. Webster, "Climate Science and the Uncertainty Monster", Bulletin of the American Meteorological Society, vol. 92, pp. 1667-1682, 2011. http://dx.doi.org/10.1175/2011BAMS3139.1
  4. G. Hegerl, P. Stott, S. Solomon, and F. Zwiers, "Comment on “Climate Science and the Uncertainty Monster” J. A. Curry and P. J. Webster", Bulletin of the American Meteorological Society, vol. 92, pp. 1683-1685, 2011. http://dx.doi.org/10.1175/BAMS-D-11-00191.1

Filed Under: Climate modelling, Climate Science, Instrumental Record, IPCC

“Vision Prize”, an online poll of scientists about climate risk

22 Jan 2012 by group

A group of researchers at Carnegie Mellon University is trying to get a better understanding of the views of earth scientists regarding various climate change topics. They have set up an ongoing poll to do this, called Vision Prize. It’s a short (10 question) poll, covering topics like the rate of CO2 increase, predicted future temperatures, sea ice and sea level states, and hurricane frequencies. Early participants can designate a $20 donation from the group to a charity of their choice, upon completion. Please take a few minutes to help them out if qualified.

Filed Under: Climate Science

The dog is the weather

17 Jan 2012 by rasmus

Update January 27: There is also another recent dog-based animations from Victoria (southeast Australia) explaining some of the key drivers of our climate and how some are changing.

A TV series that ran on Norwegian TV (NRK) last year included a simple and fun cartoon that demonstrates some important concepts relative to weather and climate:

In the animation, the man’s path can be considered as analogous to a directional climatic change, while the path traced by his dog’s whimsical movements represent weather fluctuations, as constrained by the man’s path, the leash, and the dog’s moment-by-moment decisions of what seems important to investigate in his small world. What might the leash length represent? The man’s momentary pause? The dog’s exact route relative to concepts of random variation? The messages in this animation are similar to the recent results of Grant Foster and Stefan Rahmstorf in ERL (see post here).

We’d also like to praise the TV-series ‘Siffer‘, hosted by an enthusiastic statistician explaining how most things in our world relate to mathematics. The series covers a range of subjects, for instance gambling theory, the Tragedy of the Commons, anecdotes about mathematical riddles, medical statistics, and construction design; it even answers why champagne from a large bottle tastes better than that from a smaller one. There is also an episode devoted to weather forecasting and climate.

Success in understanding our universe often depends on how the ‘story’ about it is told, and a big part of that often involves how mental images are presented. Mathematics and statistics can describe nature in great detail and “elegance”, but they are often difficult and inaccessible to the average person. Conversely, the man-and-dog animation is intuitive and easy to comprehend. Similarly, Hans Rosling’s Fun with Stats provides some very nice demonstrations of how to convey meaning via the creative display of numbers.

Filed Under: Climate impacts, Communicating Climate, El Nino, Greenhouse gases, Tutorials

Open Climate 101 Online

16 Jan 2012 by david

Almost 3000 non-science major undergraduates at the University of Chicago have taken PHSC13400, Global Warming: Understanding the Forecast, since Ray Pierrehumbert and I (David Archer) first developed it back in 1995. Since the publication of the textbook for the class in 2005 (and a much-cleaned-up 2nd edition now shipping), enrollment has gone through the roof, it’s all I’ve been able to teach the last few years, trying to keep up with demand. I hear it is the largest class on campus, with 4-500 students a year out of an annual class of only around 1400. Now the content of this class is being served to the internet world at large: Open Climate 101.

[Read more…] about Open Climate 101 Online

Filed Under: Climate Science

An online model of methane in the atmosphere

11 Jan 2012 by david

I’ve put together an easy-to-play-with online model of methane in the atmosphere. I’m going to use it for teaching along with the rest of the Understanding the Forecast webmodels, but it was designed to be relevant to the issue of abrupt new methane burps as we’ve been ruminating about lately on Realclimate. [Read more…] about An online model of methane in the atmosphere

Filed Under: Climate Science

An Arctic methane worst-case scenario

7 Jan 2012 by david

Let’s suppose that the Arctic started to degas methane 100 times faster than it is today. I just made that number up trying to come up with a blow-the-doors-off surprise, something like the ozone hole. We ran the numbers to get an idea of how the climate impact of an Arctic Methane Nasty Surprise would stack up to that from Business-as-Usual rising CO2

[Read more…] about An Arctic methane worst-case scenario

Filed Under: Arctic and Antarctic, Carbon cycle, Climate Science, Greenhouse gases

Much ado about methane

4 Jan 2012 by david

Methane is a powerful greenhouse gas, but it also has an awesome power to really get people worked up, compared to other equally frightening pieces of the climate story. [Read more…] about Much ado about methane

Filed Under: Climate Science

Unforced variations: Jan 2012

2 Jan 2012 by group

First open thread of 2012, so perhaps some discussion of the highlights and lowlights of 2011 are in order? Top 5 lists welcome…

Filed Under: Climate Science, Open thread

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