Saturday, December 22, 2007

"Global Warming," Close to Home

Arnold Kling writes:
My view of climate change is that we have about three data points--an increase in temperatures from 1900-1940, and slight decrease from 1940-1970, and a recent increase. There are a lot of variables that could affect climate, and I wonder how we can be confident about our understanding of the process, given that we have only those three data points to work with.
The weather station nearest my home has been recording temperatures since 1854. The average annual data reported for that station are consistent with Kling's statement: a warming trend from 1854 through 1933, a cooling trend from 1934 through 1979, and a warming trend from 1980 through 2007. Like Kling, I wonder how that pattern supports the theory that "global warming" is caused mainly by the rise in atmospheric CO2, a rise that could not have been reversed for 30-40 years if caused by human activity.

There are, in any event, many more relevant observations than those gleaned by weather stations. And those observations (from geological deposits and ice cores) cover much longer spans than 150 years. (See this post, for example.) What it all adds up to is this:
  • The current warm period is neither exceptionally warm nor caused by human activity.
  • We are in a phase of a climatic cycle that is determined mainly by solar activity and the position of our solar system within the Milky Way.
  • That phase probably will end relatively soon (a matter of years or decades, not centuries or millenia).
  • All we see when we look at (flawed and inconsistently recorded) temperature data from the past 100-150 years is the tail end of the phase through which we are passing.
By the way, the highest average monthly temperatures recorded by my local weather station are as follows (in degrees Fahrenheit):
January, 59.6 (1923)
February, 62.3 (1999)
March, 68.4 (1907)
April, 75.9 (1967)
May, 80.6 (1996)
June, 86.4 (1998)
July, 89.1 (1860)
August, 88.3 (1999)
September, 84.2 (1911)
October, 77.0 (1931)
November, 68.2 (1927)
December, 65.5 (1889)
Note the lack of record highs after 1999.

Also, half of the eighteen warmest years on record (years with an average temperature more than one standard deviation above the mean for 1854-2007) occurred before 1980.

Related reading, from around the web:
"The Courage to Do Nothing" (14 Dec 2007)
"Has Global Warming Stopped?" (19 Dec 2007)
"U.S. Senate Report: Over 400 Prominent Scientists Disputed Man-Made Global-Warming Claims in 2007" (20 Dec 2007)
"Good News! Earth Not Flat" (21 Dec 2007)

Posts at Liberty Corner:
"'Warmism': The Myth of Anthropogenic Global Warming" (23 Aug 2007)
"Re: Climate 'Science'" (19 Sep 2007)
"More Evidence against Anthropogenic Global Warming" (25 Sep 2007)
"Yet More Evidence against Anthropogenic Global Warming" (04 Oct 2007)

Plus, many more in this category.