I suppose I should say it again: 1. We are not certain whether the Earth is warming or cooling; it requires sophisticated computer models to determine how to combine the data in order to fabricate (I think of no better word) a single figure of merit to be called the Earth's temperature for any given year. Given what you do with those models, you can obtain a fairly wide spread of figures. 2. We do know that in historical times the Earth has been much colder and much warmer than now. It was considerably warmer during the Medieval Warm period (roughly 800 - 1325) and considerably colder during the Little Ice Age (roughly 1400 - 1800). We have a great deal of historical data, including freezing of the brackish water canals of Holland, the freezing over of the Hudson River and Great Lakes during the French and Indian and Revolutionary Wars, crop data and growing seasons, Almanacs, etc. We have less detailed but equally convincing data for the Medieval Warm period, the most dramatic being the Greenland dairy farms started by Lief "The Lucky" Ericson and his father Eric the Red. Note that the Gulf Stream doesn't have much influence over western Greenland. 3. The current warming trend began about 1800 and peaked about 1900, and by 1970 the "consensus" was that the warming trend over and a cooling trend had begun; and we might be heading for a new Little Ice Age. 4. Arrhenius back about 1900 calculated that increased CO2 could cause a greenhouse effect that might have the effect of warming the Earth by about 1 degree Centigrade. Since then we have had much more sophisticated computer models. Most of them give about the same answer and range of effects as Arrhenius got on the back of an old envelope. 5. If I had to choose between 2 degree warmer and 2 degrees cooler I'd take warmer. If I had to choose between higher sea levels and 5 degrees warmer and forty feet of ice over much of Canada and the northern US, I'd take warmer. It's easier to prepare for warmer than warmer than colder. 6. Longer growing seasons are better (more food available) than shorter. The longer growing seasons certainly had an effect in ending the Dark Ages. 7. I don't know what the climate changes were between the high times of the Roman Empire and the long fall and collapse, but I'd wager reasonable sums that it was getting colder, the growing seasons were getting shorter, food was getting scarcer, people had to work harder, etc., and this trend continued until the Medieval Warm began. This paragraphs is pure speculation and is not integral to any of my conclusions (although if it were shown to be true it would be an indicator). 8. If the US signed the Kyoto Treaty the effect on Global Warming would be lost in the noise of the economic consequences and political backlash. 9. If we are really concerned with CO2, we have technical means (such as seeding the oceans with nutrients) to cause increased absorption of CO2. These are much more effective than limiting energy consumption in the United States, particularly when China and India and "developing" countries are allowed to burn all the carbon they want. 10. There are good reasons for developing more nuclear power without regard to reducing CO2 production; interestingly the advocates of CO2 reduction from Global Warming are not fervent supporters of nuclear power. http://www.jerrypournelle.com/mail/mail452.html#Friday =================================================================== 420,000 years of Temperature Data Graphed... Dear Jerry, This fellow graphed out 420,000 years of Antarctic ice core data (By way of Kate MacMillan at www.smalldeadanimals.com ): http://captaincapitalism.blogspot.com/2007/01/one-more-time-for-stupid-people.html : Here's the full-sized graph: http://photos1.blogger.com/photoInclude/x/blogger/7944/562/1600/533125/Graph1.jpg Apparently the y-axis label has the wrong units; it is the temperature difference from the present, rather than temperature change per year. The raw data are here: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/deutnat.txt From the readme file for the data: "...Deuterium - data : file « deutnat.txt » Column 1 -Depth (m) Column 2 -Ice Age (GT4) Column 3 –Deuterium content in ‰ SMOW (Standard Mean Ocean Sea Water). Deuterium measurements have been performed on three adjacent cores 3G, 4G and 5G (see Figure 1 of Jouzel et al., 1996). It combines results successively published in Jouzel et al. (1987, 1993 and 1996). Column 4 -Temperature difference wrt the mean recent time value (i.e. corresponding departure from –438 ‰ mean deuterium value) Deuterium data is from core 3G between 138 and 2083 meters below surface (mbs) (with one long missing section between 312 and 320 mbs), from core 4G between 8 and 138 mbs and between 1920 and 2546 mbs and from core 5G between 2504 and 2757 mbs. Ash layers help to make link between cores. No correction was applied for 3G and 4G core taken as reference depth. For 5G samples, a value of 3.41 m have been added to the depth measured in the field below depth of 2500 m. Deuterium values (column 3) have been measured on ice samples of length comprised between 0.5 and 2 m (down to 2080 m) then every 1 m. Data was re-interpolated on 1m intervals afterwards. The ice recovery is 85% or higher. Measurement accuracy is of ± 0.5‰ SMOW (1 s). From the surface down to 7 m a constant value (derived from surface and pits samples) of -438.0 ‰ is reported. The temperature change indicated in column 4 (temperature above the inversion). This temperature is calculated using a deuterium/temperature gradient of 9‰/°C after accounting for the isotopic change of sea-water. No correction for the influence of the geographical position of the ice was applied..." ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/readme_petit1999.txt Nice cyclical behavior. Based on past trends, it looks like we might be due for some cooling. Cheers, Rod Schaffter