Observational Estimate of Transient Climate Response

Prof. Jonathan Gregory, NCAS-Climate reading, Met Office Hadley Centre

We have shown that the transient climate sensitivity (TCR) of the real world can be estimated from the rate of global warming in the last few decades. The TCR is a standard benchmark used to compare model simulations of the rate of warming in response to increasing carbon dioxide concentration. Similar estimates for this quantity are obtained using our method based on observation of climate change as is predicted by the climate models assessed by IPCC (2007). As the methods are independent, this is a useful corroboration, and increases confidence in IPCC projections of climate change. Our result suggests a global warming of between 1.3 and 2.3 degrees C at the time when CO2 reaches double its pre-industrial concentration.