Thursday, March 7, 2013

Analysis finds droughts not related to man-made CO2

New Report from SPPI:

Climate alarmists contend that rising global temperatures lead to more severe and longer-lasting droughts on the basis of projections of global climate change produced by mathematical models that are primarily driven by increases in the atmosphere's CO2 concentration; and with respect to the western United States, there has been growing interest in understanding drought in that part of the country in light of the pronounced impact it has had there in recent decades. Therefore, many scientists have conducted research to attempt to better understand the characteristics of historic hydrologic variability in this important region, so that a more proper evaluation can be made of how unusual, unnatural or unprecedented droughts of the recent past have been, which droughts climate alarmists typically claim have been made worse - or even been entirely caused - by CO2-induced global warming. In the following pages, this claim is evaluated by reviewing what scientists have learned in this regard from various studies that have examined historic droughts across the western United States, organizing our review into several sub-domains within the overall region of study.

From the conclusions:

Real clarity, however, comes when the turn-of-the-century drought is compared to droughts of the prior millennium. Cook et al. (2009) write that "perhaps the most famous example is the 'Great Drouth' (sic) of AD 1276-1299 described by A.E. Douglass (1929, 1935)." Yet this 24-year drought was eclipsed by the 38-year drought that was found by Weakley (1965) to have occurred in Nebraska from AD 1276 to 1313, which the authors say "may have been a more prolonged northerly extension of the 'Great Drouth'." But even these multi-decade droughts truly pale in comparison to the "two extraordinary droughts discovered by Stine (1994) in California that lasted more than two centuries before AD 1112 and more than 140 years before AD 1350." And each of these megadroughts, as Cook et al. (2009) describe them, occurred, in their words, "in the so-called Medieval Warm Period." And they add that "all of this happened prior to the strong greenhouse gas warming that began with the Industrial Revolution [authors' italics]."

Given that the above-referenced medieval megadroughts "occurred without any need for enhanced radiative forcing due to anthropogenic greenhouse gas forcing" -- because, of course, there was none at that time - Cook et al. (2009) rightfully conclude that "there is no guarantee that the response of the climate system to greenhouse gas forcing will result in megadroughts of the kind experienced by North America in the past." And if the world's climate alarmists refuse to acknowledge this possibility and continue to claim that global warming will most assuredly trigger the occurrence of medieval-like Real clarity, however, comes when the turn-ofthe-century drought is compared to droughts of the prior millennium.14 megadroughts, they will also have to acknowledge that the Medieval Warm Period of a thousand years ago had to have been much warmer than the Current Warm Period has been to date. But this acknowledgement destroys yet another of their claims, i.e., that the Earth is currently warmer than it has been for one (Mann et al., 1999) to two (Mann and Jones, 2003) millennia.

So when consulting the real world on the matter, climate alarmists find themselves positioned squarely between the proverbial rock and a hard place, with nowhere to run, no place to hide, because their contentions of present and future drought in the western United States are simply untenable.





  4. mega droughts more common during Little Ice Age