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FAQ on climate models

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Translations: (Svenska)

We discuss climate models a lot, and from the comments here and in other forums it’s clear that there remains a great deal of confusion about what climate models do and how their results should be interpreted. This post is designed to be a FAQ for climate model questions – of which a few are already given. If you have comments or other questions, ask them as concisely as possible in the comment section and if they are of enough interest, we’ll add them to the post so that we can have a resource for future discussions. (We would ask that you please focus on real questions that have real answers and, as always, avoid rhetorical excesses).

Part II is here.

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What links the retreat of Jakobshavn Isbrae, Wilkins Ice Shelf and the Petermann Glacier?

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Guest commentary from Mauri Pelto

Changes occurring in marine terminating outlet glaciers of the Greenland Ice Sheet and ice shelves fringing the Antarctic Peninsula have altered our sense of the possible rate of response of large ice sheet-ice shelf systems. There is a shared mechanism at work that has emerged from the detailed observations of a number of researchers, that is the key to the onset and progression of the ice retreat. This mechanism is shared despite the vastly different nature of the environments of Jakobshavns Isbrae, Wilkins Ice Shelf and the Petermann Glacier.
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Palin on Global Warming

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Translations: (Italian)

Here at RealClimate we understandably have an intense interest in the positions of the Presidential and Vice-Presidential candidates regarding global warming and carbon emissions. What the stance bodes for future action on climate change is consequential in itself, but beyond that the ability to use sound science in this case serves as a bellweather for the candidates’ whole approach to science. Whatever else you can say about the candidates, it has been encouraging that both John McCain and Barack Obama favor mandatory action to reduce US carbon emissions.

But, enter Gov. Sarah Palin, McCain’s pick for VP. Palin’s position on global warming has been stated quite clearly in this recent interview with the publication Newsmax , where she says “A changing environment will affect Alaska more than any other state, because of our location. I’m not one though who would attribute it to being man-made.” How is this to be reconciled with McCain’s position? Do they just agree to differ? What does this bode for future actions if McCain were to win the election, especially in view of the fact that, in a Cheney-esque way, Palin is likely to be put in charge of energy policy? The recent vice-presidential debate sheds some light on the issue. A full transcript of the debate is here.

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Simple Question, Simple Answer… Not

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Translations: (Français) (Japanese) (Finnish) (Czech)

Guest commentary by Spencer R. Weart, American Institute of Physics

I often get emails from scientifically trained people who are looking for a straightforward calculation of the global warming that greenhouse gas emissions will bring. What are the physics equations and data on gases that predict just how far the temperature will rise? A natural question, when public expositions of the greenhouse effect usually present it as a matter of elementary physics. These people, typically senior engineers, get suspicious when experts seem to evade their question. Some try to work out the answer themselves (Lord Monckton for example) and complain that the experts dismiss their beautiful logic.

The engineers’ demand that the case for dangerous global warming be proved with a page or so of equations does sound reasonable, and it has a long history. The history reveals how the nature of the climate system inevitably betrays a lover of simple answers.

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How much will sea level rise?

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Translations: (Español) (Italian)

… is the question people have been putting a lot of thought into since the IPCC AR4 report came out. We analysed what was in the report quite carefully at the time and pointed out that the allowance for dynamic ice sheet processes was very uncertain, and actually precluded setting a upper limit on what might be expected. The numbers that appeared in some headlines (up to 59 cm by 2100) did not take that uncertainty into account.

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Weekend round-up

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A few interesting pieces from around the web relevant to some previous postings:

  • The latest satellite imagery from the Wilkins Ice Sheet (discussed recently) is not looking good. And most curiously the collapse is happening in winter.
  • The Weather Channel “Forecast Earth” team make a valiant attempt to explain the problems and promise for regional climate change projections by 2050. See our post on the general subject from last year).
  • And for those of you following the various sagas of political interference in the communication of climate science, a nice interactive graphic summary, courtesy of UCS.

Next week will be a little quiet – it is mid-summer after all – so apologies in advance if the moderation is a somewhat slow. You may also note that we have instituted a “captcha” step to the commenting process. This uses reCAPTCHA which as well as providing protection against spam, helps with the digitization of old books.

All-paper salutes to the environment

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The Onion last week had a great (recycled) spoof on the various ‘green’ special issues being published but, not to be outdone, the contributors to RealClimate have also been busy producing paper products about the environment.

Surprisingly perhaps, as well as having day jobs and writing for this blog, collectively we have written a number of popular science books about climate change. Some of these have already been published, but there are a few more “in the pipeline”. We try not to overdo self-promotion on this website (for instance, we don’t blog about most of our own technical publications) but since these projects are synergistic with our aims here, it makes sense to let people know what we’ve been up to. We have therefore set up a page listing “Our Books” that we will keep up-to-date as more titles become available. It’s also linked from the new animated gif image on the side bar.

Ice Shelf Instability

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Guest contribution from Mauri S. Pelto

Ice shelves are floating platforms of ice fed by mountain glaciers and ice sheets flowing from the land onto the ocean. The ice flows from the grounding line where it becomes floating to the seaward front, where icebergs calve. For a typical glacier when the climate warms the glacier merely retreats, reducing its low elevation, high melting area by increasing its mean elevation. An ice shelf is nearly flat and cannot retreat in this fashion. Ice shelves cannot persist unless the entire ice shelf is an accumulation zone, where snowpack does not completely melt even in the summer.


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Butterflies, tornadoes and climate modelling

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Ed Lorenz hiking Many of you will have seen the obituaries (MIT, NYT) for Ed Lorenz, who died a short time ago. Lorenz is most famous scientifically for discovering the exquisite sensitivity to initial conditions (i.e. chaos) in a simple model of fluid convection, which serves as an archetype for the weather prediction problem. He is most famous outside science for the ‘The Butterfly Effect’ described in his 1972 paper “Predictability: Does the Flap of a Butterfly’s Wings in Brazil Set Off a Tornado in Texas?”. Lorenz’s contributions to both atmospheric science and the mathematics of dynamical systems were wide ranging and seminal. He also directly touched the lives of many of us here at RealClimate, and both his wisdom, and quiet personal charm will be sorely missed.

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