I'll let Hoerling tell you why hansen is up to his old climate tricks
Martin Hoerling on James Hansen’s ‘game over’ thinking
This is a word document prepared by Dr. Martin Hoerling of NOAA and provided to the New York Times is response to Dr. James Hansen’s “Game Over for The Climate” essay. Since much of the full response has not seen daylight, I asked Dr. Hoerling if I could republish it here and he graciously agreed. – Anthony
Guest post by Dr. Martin HoerlingToo much to post here, you will need to follow the link, but I will give his summaries.
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Summary
The claim in the Hansen NYT piece that the Midwest would be a dustbowl in coming decades thus runs contrary to peer reviewed literature and recent assessments by the U.S. Global Research Program that emerged from the synthesis of current understanding by an expert team of scientists.
Figure 1. The relative change in runoff in the twenty-first century expressed as the ensemble (arithmetic) mean of relative change (percentage) in runoff for the period 2041–60, computed as 100 times the difference between 2041–60 runoff in the SRESA1B experiments and 1900–70 runoff in the 20C3M experiments, divided by 1900–70 runoff. Based on Fig. 4 from Milly et al. (2005). [Milly, P, K. Dunne, A. Vecchia, Nature, 438, 2005, doi:10.1038/nature04312]. Left-side illustrates runoff change for drainage basin scale, and right side for geopolitical state scales.
Regarding observed changes in climate of the Great Plains, I stated:
“Indeed, that region (Great Plains) has seen a general increase in rainfall over the long term, during most seasons (certainly no material decline). Also, for the warm season when evaporative loss is especially effective, the climate of the central Great Plains has not become materially warmer (perhaps even cooled) since 1900. In other words, climate conditions in the growing season of the Central Great Plains are today not materially different from those existing 100 years ago. This observational fact belies the expectations, from climate simulations, and in truth, our science lacks a good explanation for this discrepancy. “
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Summary
The certainty language expressed in the Hansen NYT piece about the coming dustbowl fate for the Great Plains region and Midwest is contrary to the low confidence of regional climate change projections for coming decades as documented in USGCRP and IPCC reports. Not only are various regional patterns of trends that have been observed over the last century poorly understood, but the projections of regional changes in coming decades are highly uncertain.
Figure 2. The 1901-2010 trends in summertime (June-August) daily averaged surface temperature (°C/110 yrs; top) and rainfall (% of change over 110 yrs, bottom). Trends are plotted at available station sites, using the GHCNv3 data. Cooling (warming) trends shown in blue (red), and increased (decreased) rainfall shown in blue (red).
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Summary
The global warming signal is much smaller than the typical daily variability of surface air temperature over the United States. Most of the magnitude of daily weather extremes owes its causes to natural internal fluctuations and not to global warming. A possible exception could be imagined if global warming were also to increase the variability of daily temperatures (and not just increase the mean temperatures), but no compelling evidence to such effects has been shown. While globally averaged temperatures have risen during the past century, the cause for which is very likely human-induce climate change, the signal of this change is still barely audible among the loud noise of daily, backyard weather fluctuations.
Weather, of course, is more than temperature variability. While this discussion has involved temperature, weather involves rain, storms, winds, severe convection, clouds among others. In this regard, it is important to reiterate the statement in IPCC SREX (2012) in their Executive Summary which states that “many weather and climate extremes are the result of natural climate variability”, and that “even if there were no anthropogenic changes in climate, a wide variety of natural and weather extremes would still occur”.
Figure 3. The daily surface temperature variability during 1901-2010 averaged for all months during January-December (°C, top), and the ratio of that daily variability to the magnitude of the observed global warming signal (nondimensional). The variability is the standard deviation of daily temperature fluctuations calculated for each calendar month, and averaged across all months. The global mean warming signal of +0.51°C is derived from the NCDC analysis of the 2011 annual mean global averaged surface temperature departure relative to a 20th Century climatology (see http://www.ncdc.noaa.gov/sotc/global/2011/13)
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Summary
Analysis of various forced model simulations indicates that human influences did not contribute substantially to the magnitude of the Russian heat wave. Even accounting for a possible stronger warming signal, as suggested by Rahmsdorf and Coumou, these were still appreciably smaller than the peak magnitude of the event (which reached 10°C over Moscow during July). Barriapedro et al. (2011) conclude that the magnitude of the 2010 event was so extreme that despite an increase in temperatures due to human climate change, the likelihood of an analog over the same region remains fairly low until the second half of the 21st century. These results are thus consistent also with the Hawkins and Sutton (2012) results regarding the time of emergence of a climate change signal at local scales.
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http://wattsupwiththat.com/2012/08/13/martin-hoerling-on-james-hansens-game-over...