This post is not about the recent trend in global temperature or what the Berkeley data actually reveal about it. I already did that. This post is about the real problem with the public debate over global warming.



Judith Curry said “Our data show the pause” (her words, said to a reporter for the Daily Mail), refering to the Berkeley data of global average surface temperature over land areas. The phrase “pause” refers to a halting of global warming. She used that claim to accuse Richard Muller (leader of the Berkeley Earth Surface Temperature project) of “hiding the decline” (also her words, said to a reporter for the Daily Mail). She insisted that “There is no scientific basis for saying that warming hasn’t stopped” (also her words, said to a reporter for the Daily Mail).

As soon as I asked her (on her blog) what was the scientific basis for her claims, she started running away from her own words. But she wouldn’t retract them. Instead she replaced claims of “pause” and “stopped” with “There has been a lag/slowdown/whatever you want to call it in the rate of temperature increase since 1998” (her words on her own blog).

Here’s the Berkeley data from January 1975 through March 2010 (the final two data points, for April and May 2010, have such large uncertainty that they’re meaningless and should be omitted from analysis):

Click the graph for a larger, clearer view. Let’s estimate the trend before 1998 by least-squares regression using only pre-1998 data, call that the “model” trend, and plot it as a blue line:

Let’s extend that line to the future, call that the “predicted” trend, and plot it as a green line:

Finally, let’s compute the trend using only the data after 1998, call that the “observed” trend, and plot it as a red line:

The problem with the “debate” about global warming is that Judith Curry gets to call that a “pause.” She didn’t say “maybe.” She gets to use that claim to accuse another scientist of hiding something. She insists on a “scientific basis” for his claims but won’t apply the same standard to herself. When she’s asked point-blank for the scientific basis of her claims she changes the subject. When she’s shown the error of her ways she refuses to admit it. Her claims are publicized worldwide.

It’s not a crime. It’s a sin.