Dr. James Hansen and Reto Ruedy of NASA GISS have written a paper (non peer reviewed) with a remarkable admission in it. It is titled Global Temperature Update Through 2012.
Here is the money quote, which pretty much ends the caterwauling from naysayers about global temperature being stalled for the last decade.
The five-year mean global temperature has been flat for the last decade, which we interpret as a combination of natural variability and a slow down in the growth rate of net climate forcing.
Gosh, I thought Hansen had claimed that “climate forcings” had overwhelmed natural variability?
In 2003 Hansen wrote a widely distributed (but not peer reviewed) paper called Can We Defuse the Global Warming Time Bomb? in which he argues that human-caused forcings on the climate are now greater than the natural ones, and that this, over a long time period, can cause large climate changes.
As we shall see, the small forces that drove millennial climate changes are now overwhelmed by human forcings.
According to Hansen’s latest essay, apparently not. So much for “da bomb”.
Here are some other interesting excerpts from his recent essay, Bob Tisdale take note:
An update through 2012 of our global analysis reveals 2012 as having practically the same temperature as 2011, significantly lower than the maximum reached in 2010. These short-term global fluctuations are associated principally with natural oscillations of tropical Pacific sea surface temperatures summarized in the Nino index in the lower part of the figure. 2012 is nominally the 9th warmest year, but it is indistinguishable in rank with several other years, as shown by the error estimate for comparing nearby years. Note that the 10 warmest years in the record all occurred since 1998.
The current stand-still of the 5-year running mean global temperature may be largely a consequence of the facr [sic] that the first half of the past 10 years had predominantly El Nino conditions, and the second half had predominantly La Nina conditions.
The approximate stand-still of global temperature during 1940-1975 is generally attributed to an approximate balance of aerosol cooling and greenhouse gas warming during a period of rapid growth of fossil fuel use with little control on particulate air pollution, but quantitative interpretation has been impossible because of the absence of adequate aerosol measurements.
That last part about 1940-1975 is telling, given that we now have a cleaner atmosphere, and less aerosols to reflect sunlight, it goes without saying that more sunlight now reaches the surface. Since GISS is all about the surface temperature, that suggests (to rational thinkers at least) that some portion of the surface temperature rise post 1975 is due to pollution controls being enacted.
But, he’s still arguing for an imbalance, even though flatness abounds. Seems like equilibrium to me…
Climate change expectations.
The continuing planetary imbalance and the rapid increase of CO2 emissions from fossil fuel assure that global warming will continue on decadal time scales. Moreover, our interpretation of the larger role of unforced variability in temperature change of the past decade suggests that global temperature will rise significantly in the next few years as the tropics moves inevitably to the next El Nino phase.
Except when natural forcings overwhelm the human component of course.