There are two very important concepts here:
- Colder weather is more extreme
- The well documented US cooling trend from 1930 to the present, is not compatible with the hockey stick.
Hansen wrote this in 1999
Yet in the U.S. there has been little temperature change in the past 50 years, the time of rapidly increasing greenhouse gases — in fact, there was a slight cooling throughout much of the country (Figure 2). We caution that linear trends, as in Figure 2, can mask temporal detail. Indeed, Figure 1(b) indicates that the last 20 years have seen a slight warming in the U.S. Nevertheless, our analysis (Hansen et al., 1999a), summarized in Figures 1 and 2, makes clear that climate trends have been fundamentally different in the U.S. than in the world as a whole.