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Michael Crichton’s State of Confusion

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Translations: (Français)

In a departure from normal practice on this site, this post is a commentary on a piece of out-and-out fiction (unlike most of the other posts which deal with a more subtle kind). Michael Crichton’s new novel “State of Fear” is about a self-important NGO hyping the science of the global warming to further the ends of evil eco-terrorists. The inevitable conclusion of the book is that global warming is a non-problem. A lesson for our times maybe? Unfortunately, I think not.

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Climate Change Disinformation

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by Michael Mann and Gavin Schmidt
As highlighted in the introduction to the site, we seek to clarify the findings of scientists who study the earth’s climate, and have an informed view on the science of climate change. Additionally we will speak out where we feel that the public discourse surrounding the science is being detrimentally impacted by the shrill voices and disinformation campaigns of the “partisan think-tanks or other interested parties”.

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Welcome to RealClimate

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Translations: (Français)

Climate science is one of those fields where anyone, regardless of their lack of expertise or understanding, feels qualified to comment on new papers and ongoing controversies. This can be frustrating for scientists like ourselves who see agenda-driven ‘commentary’ on the Internet and in the opinion columns of newspapers crowding out careful analysis.

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Comment policy

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  1. Comments are moderated. Comments are periodically reviewed, but especially at weekends, evenings and holidays, there may be some delay in approving otherwise non-contentious posts. Please be patient.
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revised 01/06/11

Weren’t temperatures warmer than today during the “Medieval Warm Period”?

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Translations: (Français)

This is one of a number of popular myths regarding temperature variations in past centuries. At hemispheric or global scales, surface temperatures are believed to have followed the “Hockey Stick” pattern, characterized by a long-term cooling trend from the so-called “Medieval Warm Period” (broadly speaking, the 10th-mid 14th centuries) through the “Little Ice Age” (broadly speaking, the mid 15th-19th centuries), followed by a rapid warming during the 20th century that culminates in anomalous late 20th century warmth. The late 20th century warmth, at hemispheric or global scales, appears, from a number of recent peer-reviewed studies, to exceed the peak warmth of the “Medieval Warm Period”. Claims that global average temperatures during Medieval times were warmer than present-day are based on a number of false premises that a) confuse past evidence of drought/precipitation with temperature evidence, b) fail to disinguish regional from global-scale temperature variations, and c) use the entire “20th century” to describe “modern” conditions , fail to differentiate between relatively cool early 20th century conditions and the anomalously warm late 20th century conditions.

OK, But we do know it was warmer than present 6000 years ago, don’t we?

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Translations: (Français)

This is yet another oft-repeated but problematic assertion based in this case on the mis-characterization of the so-called Mid-Holocene Climatic Optimum” or “Mid-Holocene Warm Period”. Paleoclimate experts now know that the mid-Holocene warmth centered roughly 8000 to 6000 years ago was probably restricted to high latitudes and certain seasons (summer in the Northern Hemisphere and winter in the southern hemisphere). Because much of the early paleoclimate evidence that was available (for example, fossil pollen assemblages) came from the Northern Hemisphere extratropics, and is largely reflective of summer conditions, decades ago some scientists believed that this was a time of globally warmer conditions. More abundant evidence now demonstrates, for example, that the tropical regions were cooler over much of the year.

[Read more…] about OK, But we do know it was warmer than present 6000 years ago, don’t we?

Are Temperature Trends affected by Economic Activity?

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In a recent paper, McKitrick and Michaels (2004, or “MM04”) argue that non-climatic factors such as economic activity may contaminate climate station data, and thus, may render invalid any estimates of surface tem­perature trends derived from these data. They propose that surface temperature trends may be linked to various local economic factors, such as national coal consumption, income per capita, GPD growth rate, literacy rates, and whether or not temperature stations were located within the former Soviet Union. If their conclusions were correct, this would hold implications for the reliability of the modern surface temperature record, an important piece of evidence indicating 20th century surface warming. However, numerous flaws with their analysis, some of them absolutely fundamental, render their conclusions invalid.

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Why does the stratosphere cool when the troposphere warms?

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Translations: (Français)

This post is obsolete and wrong in many respects. Please see this more recent post for links to the answer.

14/Jan/05: This post was updated in the light of my further education in radiation physics.
25/Feb/05: Groan…and again.

Recent discussions of climate change (MSU Temperature Record, ACIA) have highlighted the fact that the stratosphere is cooling while the lower atmosphere (troposphere) and surface appear to be warming. The stratosphere lies roughly 12 to 50 km above the surface and is marked by a temperature profile that increases with height. This is due to the absorbtion by ozone of the sun’s UV radiation and is in sharp contrast to the lower atmosphere. There it generally gets colder as you go higher due to the expansion of gases as the pressure decreases. Technically, the stratosphere has a negative ‘lapse rate’ (temperature increases with height), while the lower atmosphere’s lapse rate is positive.

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The Surface Temperature Record and the Urban Heat Island

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There are quite a few reasons to believe that the surface temperature record – which shows a warming of approximately 0.6°-0.8°C over the last century (depending on precisely how the warming trend is defined) – is essentially uncontaminated by the effects of urban growth and the Urban Heat Island (UHI) effect. These include that the land, borehole and marine records substantially agree; and the fact that there is little difference between the long-term (1880 to 1998) rural (0.70°C/century) and full set of station temperature trends (actually less at 0.65°C/century). This and other information lead the IPCC to conclude that the UHI effect makes at most a contribution of 0.05°C to the warming observed over the past century.

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