Climate scientist Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies (GISS), has used a blog post to launch a blistering attack on fellow climate scientist John Christy from the University of Alabama in Huntsville (UAH).
Schmidt’s posting on the realclimate.org blog yesterday (7 May 2016) describes Christy’s use of graphs presented to the US Congress earlier this year as “misleading”.
The graphs were presented by Christy to US House Committee on Science, Space and Technology on 16 February 2016. They compare climate model predictions for global warming with satellite data on global temperatures.
Christy argued in his testimony that the graphs show that models, on average, predict a warming of the atmosphere that is about 2.5 times faster than that observed from satellites measurements – the implication being that climate models exaggerate the risks of future climate change. Schmidt states in his blog that Christy’s graphs are misleading because of the choice of baseline, the use inconsistent data smoothing and the treatment of data and model uncertainties.
Christy’s use of this comparison between satellite measurements and model forecasts has attracted criticism over the use of satellite data for global temperature analysis. In his House testimony in February, Christy explained in some detail why satellite-derived temperatures are more reliable indicators of global warming than surface thermometers.
Schmidt, a forceful advocate of the case for human driven climate change and a supporter of surface temperature measurements, and Christy, an acknowledged sceptic and a pioneer of satellite temperature monitoring, have crossed swords before. The debate has been sharpened by changes last year to the way NASA analyses surface temperature data which had the effect of increasing the rate of global warming shown by surface temperature measurements – a faster rate than indicated by satellites.
The row over the use of these graphs erupted in public in April when Schmidt criticised another climate scientist, Judith Curry from the Georgia Institute Of Technology, for planning to use Christy’s graphs in a presentation questioning whether models are “too sensitive” to greenhouse warming. Schmidt tweeted then that “use of Christy’s misleading graph instead is the sign of partisan not a scientist”.
Gavin Schmidt’s blog on realclimate.org
John Christy’s presentation to the US House Committee on Science, Space and Technology.