A recent article (‘Global Warming: On Hold?’, Michael Reilly, Discovery News) focuses on the recent plateau of global air temperatures. After air temperatures rose dramatically since the late 1970s, culminating in a peak in 1998 caused largely by a strong El Niño event, air temperatures have stopped rising for a decade. The article centers on research findings by Kyle Swanson and Anastasios Tsonis from the University of Wisconsin-Milwaukee.
Their paper, which has been accepted for publication in the journal Geophysical Research Letters, argues that
“When the major modes of Northern Hemisphere climate variability are synchronized, or resonate, and the coupling between those modes simultaneously increases, the climate system appears to be thrown into a new state, marked by a break in the global mean temperature trend and in the character of El Niño/Southern Oscillation variability.”
Thus, as they conclude, another coupling occurred in 2001/02 which ended the warming trend that pervaded for the previous 25 years. But Swanson warns that although the trend could continue for up to 30 years, “explosive” warming will return “and be very aggressive”. Isaac Held of NOAA’s Geophysical Fluid Dynamics lab in Princeton NJ also weighs in, suggesting that some of the warming since the 1970s was due “to a free variation in climate” (read ‘natural variability’) and that warming might go on a hiatus “before rapid warming commences again.”
What strikes me as being odd is the argument that CO2-induced global warming could go into ‘hiding’ for up to 30 years and then come back at us with a vengeance. Such an argument requires (1) an admission that something at least as strong as greenhouse gases are affecting our climate and will be affecting it for some time to come and (2) that greenhouse gas forcing will ‘magically’ disappear only to return and pounce with the ferociousness of a leaping tiger. The former is a strong condemnation of both the IPCC report and the infamous ‘Hockey Stick’, both of which argue that human-induced warming is the primary, if not sole, driver of climate change. But the latter seems to violate the laws of physics where the radiative effect of greenhouse gases is expected to ‘go away’ only to return at us with an anthropomorphic vengeance. How the supposed effect of greenhouse gases could be ‘saved up’ only to be return all at once is a mystery. But the biggest mystery is that proponents now seem to admit that we may not see warming at all for up to 30 years, which will be a convenient cover to continue the ‘climate crisis’ rhetoric during an extended period of non-warming.
Swanson further states in the article that the lack of warming is unprecedented since 1950 in that cooling events were caused by volcanic activity or strong La Niñas. “This current cooling doesn’t have [a cause],” Swanson argues. Oh really? Although the Swanson and Tsonis article is still in press, let’s examine an article that was just recently published in the same journal, Geophysical Research Letters (doi:10.1029/2008GL036307, discussed at http://wattsupwiththat.com/2009/03/13/scafetta-paper-increasing-tsi-between-1980-and-2000-could-have-contributed-significantly-to-global-warming-during-the-last-three-decades/). It is by Nicola Scafetta of Duke University and Richard C. Willson of ACRIM of Coronado CA. The title of their paper is one only a solar physicist would love – “ACRIM-gap and TSI trend issue resolved using a surface magnetic flux TSI proxy model” – but the conclusion has important ramifications for the climate change debate:
“[The finding of this paper] has evident repercussions for climate change and solar physics. Increasing TSI [Total Solar Irradiance] between 1980 and 2000 could have contributed significantly to global warming during the last three decades. Current climate models [such as those used by the IPCC] have assumed that the TSI did not vary significantly during the last 30 years and have therefore underestimated the solar contribution and overestimated the anthropogenic contribution to global warming.”
Thus the warming from 1980 to 2000 may have been largely solar-driven and the subsequent pause in solar intensity of this decade may be responsible for the current cooling. Indeed, that pesky Sun keeps confounding its critics.
