Please direct inquiries to Professor Bothun.
Global Temperature Is Continuing to Rise: A Primer on Climate Baseline Instability
G. Bothun and S. Ostrander, Dept of Physics, University of Oregon
... When represented this way, it seems clear that the El Nino/La Nina cycles are superposed on a steadily increasing slope that commences somewhere in the 1980-1985 period. The claim that global warm[ing] stopped in 1998, as applied to this diagram, shows that it also stopped in 1982, then again in 1985, and then in 1991, 1998, 2001, 2003, and 2008. In other words, we see continuous evidence of “mini-peaks” (or local maxima in the parlance of time series language) in the anomaly data which are simply smoothed over and missed when one plots annual data.
The current period is most likely a local minimum with respect to the last peak and one just need wait another 12 months or so, when we will return to increasing global monthly anomalies which then will be about +1 degree C in amplitude. Note finally that this data is using a 100 year baseline which is serving to somewhat suppress the actual amplitude of the positive residuals. The main point of this article, however, is not to determine the statistically best way to define the maximum amplitude of global rises in average land temperature, but rather to point out the significant fluctuations in the baseline due to the 4 phase AMO/PDO system and the El Nino/La Nina cycle will cause local maxima and minima in any time series data involving average temperatures.
On the basis of this data it would seem that we oscillate between a local maximum and a local minimum (on timescales of a couple of years) while the underlying trend is upwards and certainly not downwards. Consistent with that conclusion is the recent data from NOAA and NASA that March 2010 was the warmest March every within the time period shown above. When other factors are considered [which affect] the future amplitude of temperature increases, such as the water vapor feedback loop and the methane release of the Arctic permafrost, the argument that global warming peaked in 1998 will prove to be both erroneous and silly.