The BBC’s Roger Harrabin has interviewed Phil “CRU” Jones and put to him a number of questions, many from a decidedly sceptical viewpoint. The questions, labelled A – W, provide many revealing answers. Here are some of the most interesting:
A – Do you agree that according to the global temperature record used by the IPCC, the rates of global warming from 1860-1880, 1910-1940 and 1975-1998 were identical?
An initial point to make is that in the responses to these questions I’ve assumed that when you talk about the global temperature record, you mean the record that combines the estimates from land regions with those from the marine regions of the world. CRU produces the land component, with the Met Office Hadley Centre producing the marine component.
Temperature data for the period 1860-1880 are more uncertain, because of sparser coverage, than for later periods in the 20th Century. The 1860-1880 period is also only 21 years in length. As for the two periods 1910-40 and 1975-1998 the warming rates are not statistically significantly different (see numbers below).
I have also included the trend over the period 1975 to 2009, which has a very similar trend to the period 1975-1998.
So, in answer to the question, the warming rates for all 4 periods are similar and not statistically significantly different from each other.
Translation: There is nothing unusual about the late 20th century warming.
B – Do you agree that from 1995 to the present there has been no statistically-significant global warming?
Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods.
Translation: There has been no statistically significant warming since 1995.
D – Do you agree that natural influences could have contributed significantly to the global warming observed from 1975-1998, and, if so, please could you specify each natural influence and express its radiative forcing over the period in Watts per square metre.
This area is slightly outside my area of expertise. When considering changes over this period we need to consider all possible factors (so human and natural influences as well as natural internal variability of the climate system). Natural influences (from volcanoes and the Sun) over this period could have contributed to the change over this period. Volcanic influences from the two large eruptions (El Chichon in 1982 and Pinatubo in 1991) would exert a negative influence. Solar influence was about flat over this period. Combining only these two natural influences, therefore, we might have expected some cooling over this period.
Translation: We don’t know what caused the warming, so it must be us.
E – How confident are you that warming has taken place and that humans are mainly responsible?
I’m 100% confident that the climate has warmed. As to the second question, I would go along with IPCC Chapter 9 – there’s evidence that most of the warming since the 1950s is due to human activity.
Translation: Despite my answer to “D”, I know which side my bread is buttered.
Read it here.






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