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The weirdest millennium

Filed under: — stefan @ 29 May 2007

Much research effort over the past years has gone into reconstructing the temperature history of the last millennium and beyond. The new IPCC report compiles a dozen reconstructions for the temperature of the Northern Hemisphere (including of course the original “hockey stick” reconstruction, despite opposite claims by the Wall Street Journal). Lack of data does not permit robust reconstructions for the Southern Hemisphere. Without exception, the reconstructions show that Northern Hemisphere temperatures are now higher than at any time during the past 1,000 years (Figure 1), confirming and strengthening the conclusions drawn in the previous IPCC report of 2001.

Fig. 1: Figure 6.10 (panel b) from the paleoclimate chapter of the current IPCC report (see there for details).

“Climate sceptics” do not like this and keep coming up with their own temperature histories. One of the weirdest has been circulated for years by German high-school teacher E.G. Beck (notorious for his equally weird CO2 curve). This history shows a medieval warm phase that is warmer than current climate by more than 1 ºC (see Figure 2). So how did Beck get this curve?

Fig. 2, modified from E.G. Beck (we added the green parts).

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Why global climate models do not give a realistic description of the local climate

Filed under: — rasmus @ 27 May 2007 - (Português)

Global climate
glasses Global climate statistics, such as the global mean temperature, provide good indicators as to how our global climate varies (e.g. see here). However, most people are not directly affected by global climate statistics. They care about the local climate; the temperature, rainfall and wind where they are. When you look at the impacts of a climate change or specific adaptations to a climate change, you often need to know how a global warming will affect the local climate.

Yet, whereas the global climate models (GCMs) tend to describe the global climate statistics reasonably well, they do not provide a representative description of the local climate. Regional climate models (RCMs) do a better job at representing climate on a smaller scale, but their spatial resolution is still fairly coarse compared to how the local climate may vary spatially in regions with complex terrain. This fact is not a general flaw of climate models, but just the climate models’ limitation. I will try to explain why this is below.

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Glacier Mass Balance: equilibrium or disequilibrium response?

Filed under: — group @ 24 May 2007

Guest Commentary from Mauri S. Pelto

I get asked at least once a day about the future prognosis for alpine glaciers and whether they have a future. I will focus here on North American glaciers whose mass balance measurements in the West from 1984-2005 indicate a declining trend. The trend suggests that all of the glaciers are out of balance and that some will disappear. The question is determining which glaciers are merely out of equilibrium and can retreat to a position of equilibrium, and which are in complete disequilibrium and will melt away? Let me explain.
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Start here

Filed under: — group @ 22 May 2007 - (Slovenčina) (Polski) (Български)

We’re often asked to provide a one stop link for resources that people can use to get up to speed on the issue of climate change, and so here is a selection. Unlike our other postings, we’ll amend this as we discover or are pointed to new resources. Different people have different needs and so we will group resources according to the level people start at.

For complete beginners:

NCAR: Weather and climate basics
Center for Climate and Energy Solutions: Global Warming basics
Wikipedia: Global Warming
NASA: Global Warming update
National Academy of Science: America’s Climate Choices (2011)
Encyclopedia of Earth: Climate Change Collection
Global Warming FAQ (Tom Rees)
Global Warming: Man or Myth? (Scott Mandia, SUNY Suffolk)
Oxford Begbrooke: Climate Basics

There is a booklet on Climate Literacy from multiple agencies (NOAA, NSF, AAAS) available here (pdf).

The UK Govt. has a good site on The Science of Climate Change (added Sep 2010).

The portal for climate and climate change of the ZAMG (Zentralaanstalt für Meteorologie und Geodynamik, Vienna, Austria). (In German) (added Jan 2011).

Those with some knowledge:

The IPCC AR4 Frequently Asked Questions (here are an excellent start. These cover:

Updates to these questions were provided in the 5th Assessment report (pdf).

The UK Royal Society and US National Academies of Science produced a joint Q&A on climate change in 2014, and an update in 2017.

RealClimate: Start with our index

Informed, but in need of more detail:

Science: You can’t do better than the IPCC reports themselves (AR5 2013, AR4 2007, TAR 2001).

History: Spencer Weart’s “Discovery of Global Warming” (AIP)

Art: Robert Rohde’s “Global Warming Art

Informed, but seeking serious discussion of common contrarian talking points:

All of the below links have indexed debunks of most of the common points of confusion:

Please feel free to suggest other suitable resources, particularly in different languages, and we’ll try to keep this list up to date.

A bit of philosophy

Filed under: — eric @ 16 May 2007

Eric Steig and Gavin Schmidt

The two of us participated last week in an interesting meeting at the University of Washington on Ethics and Climate Change. Other scientists in attendance included Dennis Hartmann, who gave an overview of the current state of the science, and sometime RealClimate contributor Cecilia Bitz. Organized by Associate Professor of Philosophy Stephen Gardiner, the conference was dedicated to the particular ethical and moral issues raised by the spectre of anthropogenic climate change. Since we aren’t philosophers by training, and since it would probably stray too far from RealClimate’s focus on science, we won’t comment in great detail. However, we thought it worth making our readers aware that there is a very interesting and growing literature on the subject. Based on their remarks at the conference, we heartily recommend checking out the papers and commentaries written by the various philosphers, scientists, and political theorists who attended. You can get abstracts of their talks on the conference web page. Below, we simply wish to note several issues raised at the conference that we found particularly interesting.
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