2
Why is detection and attribution work important?
l
lIt is another form of model evaluation
lSuccessful simulation of historical changes in climate enhances confidence in projections of future climate change
lIn an environment where there is still political debate regarding the reality of a human effect on global climate, it is imperative to have Òsound scienceÓ on the nature and causes of climate change
 I havenÕt shown you this, but the Earth is warming. We know this from detailed analyses of thermometric temperature records.
 The best information we have indicates that the EarthÕs mean near-surface temperature has increased by around 0.5oC over the last 100 years.
 Analyses of ÒreconstructedÓ temperature data from tree rings, ice cores, corals and boreholes indicate that the Earth is now warmer than at any time since at least 1400 A.D.
 I have shown you one example of a ÒfingerprintÓ study, in which model-predicted and observed patterns of temperature change have significant similarities.
 These similarities generally increase with time, and they canÕt be fully explained by the ÒnoiseÓ of natural climate fluctuations (assuming that model estimates of this noise are realistic).
 Here, IÕve shown you results for vertical cross-sections of temperature change. We and others have obtained rather similar results from analyses of geographical patterns of temperature change at the EarthÕs surface.