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Archives for June 2007

A Saturated Gassy Argument

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Translations: (Português)

A guest post by Spencer Weart, in collaboration with Raymond T. Pierrehumbert

The simple physics explanations for the greenhouse effect that you find on the internet are often quite wrong. These well-meaning errors can promote confusion about whether humanity is truly causing global warming by adding carbon dioxide to the atmosphere. Some people have been arguing that simple physics shows there is already so much CO2 in the air that its effect on infrared radiation is "saturated"— meaning that adding more gas can make scarcely any difference in how much radiation gets through the atmosphere, since all the radiation is already blocked. And besides, isn’t water vapor already blocking all the infrared rays that CO2 ever would?

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Part II: What Ångström didn’t know

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By raypierre , with the gratefully acknowledged assistance of Spencer Weart

In Part I the long struggle to get beyond the fallacious saturation argument was recounted in historical terms. In Part II, I will provide a more detailed analysis for the reader interested in the technical nitty-gritty of how the absorption of infrared really depends on CO2 concentration. At the end, I will discuss Herr Koch’s experiment in the light of modern observations.
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Storm World: A Review

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If you are a RealClimate regular, you are undoubtedly aware of our ongoing interest in the developments in the scientific understanding of potential hurricane-climate change linkages. This is an area of the science where a substantial body of significant new research has emerged even since RealClimate’s inception in late 2004. The scientific research in this area, and the media frenzy and political theatrics that have inescapably followed it, are thoughtfully placed in a broader historical context in a fascinating new book by Chris Mooney entitled Storm World: Hurricanes, Politics, and the Battle over Global Warming. Anyone who is at all interested in the scientific history that has led to our current understanding of Hurricanes and their potential linkages with climate change, will find this book a page turner. The book is a nice complement to Kerry Emanuel’s recent book Divine Wind: The History and Science of Hurricanes (which too is so readable that it lies on our coffee table). Mooney in a sense picks up where Emanuel’s left off. Like Emanuel, he explores the history of the science. But he uses this historical context, and his studies of the personalities of key actors, to explore how the current scientific debate can be traced back to a rift that has emerged over many decades between distinct communities of atmospheric scientists.
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Curve manipulation: lesson 2

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Two weeks ago, we published the first lesson in curve manipulation taught by German school teacher and would-be scientist E.G. Beck: How to make it appear as if the Medieval times were warmer than today, even if all scientific studies come to the opposite conclusion. Today we publish curve manipulation, lesson 2: How to make it appear as if 20th Century warming fits into a 1500-year cycle. This gem is again brought to us by E.G. Beck. In a recent article (in German), he published the following graph:

Notice how temperature goes up and down in beautifully regular cycles since 800 B.C.? At the bottom, they are labelled “Dansgaard-Oeschger cycles” – this refers to the Dansgaard-Oeschger events found in Greenland ice cores during the last Ice Age (but not during the last 10,000 years), about which there is a serious scientific discussion whether they are paced by a 1500-year cycle (see my paper in GRL). Beck’s curve shows a warm phase 400 BC and the next one 1200 AD – that’s 1600 years difference, so it just about fits. (I’m not endorsing his curve, by the way, I have no idea where it comes from – I’m just playing along with it for the sake of the argument). So the next warm phase should be in the year – oooops… 2700 or 2800? Hang on, how come it looks like the current warmth fits so nicely into the cycle? Shouldn’t we be right in the coldest phase? Now I see it… two little lines across the x-axis indicate that the axis has been broken there – tick-marks after the break are in 200-year intervals and before the break in 400-year intervals, and there’s also a gap of 200 missing years there. So that’s how we make the current global warming fit past climate cycles – it’s so easy!

p.s. Beck appeared on German TV last Monday, after the “Swindle” film was shown, and he is announced to appear on the program “Report München” in the first channel of public German TV next Monday (18 June), to educate the viewers about another of his fantasy graphs, namely his CO2 curve. It promises to be a must-see for friends of the unintentionally farcical.

G8 summit declaration

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We assume that many of our readers will be interested in the declaration of the G8 summit in Heiligendamm (Germany), which was agreed yesterday by the leaders of the G8 countries. We therefore document the key passages on climate change below. As usual we refrain from a political analysis, but as scientists we note that it is rewarding to see that the results of climate science are fully acknowledged by the heads of state.

The declaration states:

CLIMATE CHANGE

48. We take note of and are concerned about the recent UN Intergovernmental Panel on Climate Change (IPCC) reports. The most recent report concluded both, that global temperatures are rising, that this is caused largely by human activities and, in addition,that for increases in global average temperature, there are projected to be major changes in ecosystem structure and function with predominantly negative consequences for biodiversity and ecosystems, e.g. water and food supply.

Fighting Climate Change

49. We are therefore committed to taking strong and early action to tackle climate change in order to stabilize greenhouse gas concentrations at a level that would prevent dangerous anthropogenic interference with the climate system. Taking into account the scientific knowledge as represented in the recent IPCC reports, global greenhouse gas emissions must stop rising, followed by substantial global emission reductions. In setting a global goal for emissions reductions in the process we have agreed today involving all major emitters, we will consider seriously the decisions made by the European Union, Canada and Japan which include at least a halving of global emissions by 2050. We commit to achieving these goals and invite the major emerging economies to join us in this endeavour.

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Cockburn’s form

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Alexander Cockburn (writing in the Nation) has become the latest contrarian-de-jour, sallying forth with some rather novel arithmetic to show that human-caused global warming is nothing to be concerned about. This would be unworthy of comment in most cases, but Cockburn stands out as one of only a few left-wing contrarians, as opposed to the more usual right-wing variety. Casual readers may have thought this is a relatively recent obsession of his (3 articles and responses over the last month), however, Cockburn has significant form* and has a fairly long history of ill-informed commentary on the subject of global warming.
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