Establishment climate scientists have been correcting raw temperature data input to the Global Average Surface Temperature (GAST) models, which has had the effect of restoring the rate of increase and eliminating the near 20-year "pause" in warming. A new study (On the Validity of NOAA, NASA, and Hadley GRU Global Average Surface Temperature Data & The Validity of EPA's CO2 Endangerment Finding) strongly suggests that all or almost all the warming for the last 20 years, and a significant amount for the last 50 years, is accounted for by instrument biases and corrections. As a result, the study calls into question the EPA's "Endangerment Finding" for CO2, which justified the Obama administration's restrictive rules on carbon emissions issued just before the end of their term.
Okay, so that's a bit of a bruising lede paragraph; let's break it down.
The essential measurement on which the climate change debate is based is the Global Average Surface Temperature (GAST). Conceptually, this is really pretty simple: you just put a thermometer on every point on the surface of the earth, take continuous readings for an entire year and then divide the sum of all those readings by the number of readings.
Practically, that presents problems: that's a lot of thermometers and people use the surface of the Earth for doing other things than taking temperature readings. The reality is that the thermometers are anywhere from miles apart to thousands of miles, and they're not at all uniform. So to estimate the GAST, the temperature measurements are fed into a model, which includes corrections. When I was writing about this in 2013, the difference between GAST and the predictions of GAST was becoming too big to ignore. Climate scientists then looked for reasons and added new corrections -- but some of them were controversial.
The study presents this conclusion:
The conclusive findings of this research are that the three GAST data sets are not a valid representation of reality. In fact, the magnitude of their historical data adjustments, that removed their cyclical temperature patterns, are totally inconsistent with published and credible U.S. and other temperature data. Thus, it is impossible to conclude from the three published GAST data sets that recent years have been the warmest ever –despite current claims of record setting warming.
As with most climate research, this should be taken with a grain of salt, but the data does seem to show something I've suspected for a long time: that the corrections account for nearly all the recent warming. When your corrections to the input data appear to provide all the evidence for a phenomenon, it's time to be suspicious.