Tuesday, January 12, 2010

6. The Failure of the Forecasts

The lower blue curve and left scale in the figure show the atmospheric CO2 concentration since 1979, in parts per million by volume (ppmv), as measured by the Carbon Dioxide Research Group of Scripps Institute of Oceanography at the summit of Mauna Loa on the Big Island of Hawaii. The upper red curve and the right scale show the global temperature record since 1980, as now corrected, from instruments aboard satellites of the Earth Observing System. The data are from NOAA's National Climatic Data Center. The oscillating heavy curve is a 24-month running average of the data, and the smooth curve gives a better impression of the temperature trends. (For those interested, the curve was obtained by least-squares fitting a sixth-order polynomial to the data.)

The sharp peak in temperature in 1998 was probably due to the unusual strength of El Niño (a periodic circulation phenomenon in the Pacific), and the low temperatures in 1982 and 1993 may have been results of the volcanic eruptions of El Chichon in Mexico and Mt Pinatubo in the Philippines. The reasons for the other multi-year periods of high or low temperature are not well understood.

If we discount El Niño, the figure still shows that we have experienced a global cooling trend since 2002, despite the continued rise in CO2. In the last month or two, there has been some indication that the cooling has slowed, but it is too soon to tell whether the recent frigid weather will intensify, or whether warming will resume.

Other indicators confirm the cooling: for example, satellite measurements have shown that the area covered by Arctic sea-ice in summer has been shrinking for many years,but now demonstrate that it is growing. At its annual minimum in mid-September, 2009, the area was 11% greater than in 2008 and 23% greater than in 2007. As the area grows, the ice reflects more sunlight back into space, and the resulting cooling reduces melting. This positive feedback is too small to have much effect at the moment -- but it is probably responsible for the astonishing fact that the ice sheet will be a mile thick over most of Europe and North America within 20 years after the onset of the inevitable next ice age.

The projections by the Intergovernmental Panel on Climate Change (IPCC) during the 'Nineties totally failed to predict this cooling trend, which raises a legitimate question: if the computer models cannot forecast climate a decade ahead, why should we believe what they say about conditions a century from now?

While some of those committed to anthropogenic global warming (AGW) simply refuse to accept the plain evidence that we are now in a cooling phase, a more common response is to point out that "X of the last Y years were the warmest on record." This is another typical example of a true but deliberately misleading statement, a device often used by the AGW Lobby when it is necessary to obscure inconvenient facts. In this case, all the statement says is that years in which temperatures were near the peak were warmer than others. It is like pointing out, as if it were an important discovery, that the water comes farther up the beach shortly after high tide than it did at low tide. The obvious, shameful purpose of this inane claptrap is to mislead the public into thinking that the warming has not stopped.

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