Monday, September 9, 2013

Well Worth Reading: A Paper Just Published in Climate

Abstract:The rise in global average temperature over the last century has halted since roughly the year 2000, despite the fact that the release of CO2 into the atmosphere is still increasing. It is suggested here that this interruption has been caused by the suspension of the near linear (+ 0.5 °C/100 years or 0.05 °C/10 years) temperature increase over the last two centuries, due to recovery from the Little Ice Age, by a superposed multi-decadal oscillation of a 0.2 °C amplitude and a 50~60 year period, which reached its positive peak in about the year 2000—a halting similar to those that occurred around 1880 and 1940. Because both the near linear change and the multi-decadal oscillation are likely to be natural changes (the recovery from the Little Ice Age (LIA) and an oscillation related to the Pacific Decadal Oscillation (PDO), respectively), they must be carefully subtracted from temperature data before estimating the effects of CO2
You can read the full paper here. The paper does not claim that there is no anthropogenic global warming, but it does make a case that failure to subtract the PDO creates an inaccurate contribution of carbon dioxide to the process, and this explains why there has been no warming since 2000, and perhaps even some cooling, in spite of carbon dioxide levels continuing to rise.  Ditto for the global temperature declines after 1910 and 1970, in spite of continuing carbon dioxide level rises.

One again, another reason to see what Watts Up With That? is posting each day.

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