Last December the Trump transition team asked the Department of Energy for a list of employees who had worked on or attended meetings about how to calculate the hidden costs of carbon pollution. The doe refused, but coming from a new administration whose leader has tweeted that global warming is a Chinese hoax, this sounded like the beginning of a political witch hunt.
If so, it wouldn't be the first. In 2009, during the so-called Climategate affair, climate “skeptics” released e-mails purporting to show that scientists were manipulating data and suppressing critics (several investigations proved that these charges were groundless). In 2010 Virginia's Republican attorney general tried to get hold of records related to the work of Michael Mann of Pennsylvania State University on the groundless assumption that he, too, had manipulated data.
And in 2015 Representative Lamar Smith of Texas claimed that scientists at the National Oceanic and Atmospheric Administration had manipulated global temperature data and instigated an investigation of them. The scientists, led by Tom Karl, had published a paper that asserted that global warming since 1998 had been underestimated. The idea of a “hiatus” in warming was therefore wrong.
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Smith demanded access to the scientists' e-mail discussions and notes, hoping to find evidence of fraud. They provided the data and methods to verify their conclusions but refused to provide e-mails. Experts often argue against their own positions—this is a key part of skepticism—so e-mails offer lots of material that can be taken out of context to give a misleading impression.
The real test of a claim is to compare it with observations—to replicate it by experiment. We often have to explore many blind alleys to get to the right answer, and it frequently takes someone else to spot the errors in a study. As a result, the community generally does not fully accept a result until it has been independently verified by another group.
In a paper published in January in Science Advances, we set out to replicate the work of Karl and his colleagues. We evaluated their results by producing three different ocean temperature records of recent years, using data from buoys, satellites and Argo floats. Our results suggest that the new NOAA record most likely is the most accurate of the various sea-surface temperature reconstructions covering the past two decades and should help resolve some of the criticism that accompanied the original NOAA study.
These checks took a few weeks, and we did them in our spare time (although writing them up for publication took much longer). Compare this with the months of effort by Smith and his lawyers, whose hourly rates are many times those of paid scientists and funded by the taxpayer—a far less efficient process even if it had produced scientifically meaningful results, which it could not. Smith's actions send a disturbing message that experts should produce results that are convenient to political narratives rather than those that accurately reflect reality.
The balance of evidence supports the new NOAA temperature record. Does this mean that there never was a hiatus? That is a different question and one that is still being hotly debated in the scientific community. But the way to find out how fast the earth has been warming over the past two decades is through experimental replication—not a political investigation. And the best evidence we have says that NOAA got it right.
