In 1999, NASA’s James Hansen wrote that the US was cooling, even as greenhouse gases rapidly increased.
Whither U.S. Climate?
By James Hansen
Empirical evidence does not lend much support to the notion that climate is headed precipitately toward more extreme heat and drought
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).
The US has (by far) the most credible temperature record in the world, so this cooling was devastating to their global warming theory. NASA responded to this challenge as they always do, by tampering with the data and making the cooling disappear.