Watts Up With That?
Wednesday, Oct 21st, 2009


Craig Loehle
National Council for Air and Stream Improvement, Inc.
Reprint available from NCASI (PDF)


Global satellite data is analyzed for temperature trends for the period January 1979 through June 2009.* Beginning and ending segments show a cooling trend, while the middle segment evinces a warming trend.* The past 12*to 13*years show cooling using both satellite* data sets, with lower confidence limits that do not exclude a negative trend until 16*to 22*years.* It is shown that several published studies have predicted cooling in this time frame.* One of these models is extrapolated from its 2000 calibration end date and shows a good match to the satellite data, with a projection of continued cooling for several more decades.

Figure 6.**** Linear plus period model from Klyashtorin and Lyubushin (2003) overlaid on satellite data after intercept shift.* Dotted line is model extrapolation post-2000 calibration period end. a) UAH.* b) RSS.

Figure 6a – UAH data plus model*

Figure 6b – RSS data plus model*

Analysis of the satellite data shows a statistically significant cooling trend for the past 12 to 13 years, with it not being possible to reject a flat trend (0 slope) for between 16 and 23 years. This is a length of time at which disagreement with climate models can no longer be attributed to simple LTP. On the other hand, studies cited herein have documented a 50–70 year cycle of climate oscillations overlaid on a simple linear warming trend since the mid-1800s and have used this model to forecast cooling beginning between 2001 and 2010, a prediction that seems to be upheld by the satellite and ocean heat content data. Other studies made this same prediction of transition to cooling based on solar activity indices or from ocean circulation regime changes. In contrast, the climate models predict the recent flat to cooling trend only as a rare stochastic event. The linear warming trend in these models that is obtained by subtracting the 60–70 yr cycle, while unexplained at present, is clearly inconsistent with climate model predictions because it begins too soon (before greenhouse gases were elevated) and does not accelerate as greenhouse gases continue to accumulate. This model and the empirical evidence for recent cooling thus provide a challenge to
climate model accuracy.