The hottest topic in climate research is the observation that global average surface temperature, as well as satellite observations of temperatures in the atmosphere, has shown little or no warming during the 21st century. 

Now the political climate is heating up over the same issue. Heated words began circulating last summer, when a team of government scientists from the National Oceanic and Atmospheric Administration (NOAA), led by Thomas Karl, published a paper in Science titled “Possible Artifacts Of Data Biases In The Recent Global Surface Warming Hiatus.”   

The press release from NOAA included this statement from Karl, who is head of the National Centers for Environmental Information:   “Adding in the last two years of global surface temperature data and other improvements in the quality of the observed record provide evidence that contradict the notion of a hiatus in recent global warming trends.”

Media headlines quickly touted the Karl conclusion that science now shows the hiatus in warming never existed.

The significance of the hiatus is that it contradicted the 2007 assessment report from the Intergovernmental Panel on Climate Change (IPCC), which projected a rate of warming of 0.2oC per decade in the early part of the 21st century.  The discrepancy between the climate models and the observations raised serious questions about the climate models.

Scientists on both sides of the debate have been critical of Karl’s paper and temperature adjustments made in the new data set, particularly the ocean data analysis.

Some said that adjusting reliable ocean surface buoy data upwards to match much less reliable data from engine intake channels in ships causes an artificial upward trend in the readings.

Another recent paper used a different NOAA ocean surface temperature data set to find that since 2003 the global average ocean surface temperature has been rising at a rate that is an order of magnitude smaller than the rate of increase reported in Karl’s paper.

Clearly, scientists have much work to do to better understand the problems with historical ocean temperature data, adjust the biases among different types of measurements, and understand the differences among different data sets.

But the hiatus fuss is also telling us about the politicization of climate science.

The surface temperature data set plays a central role in the political debate over climate change. In his 2015  State of the Union address, President Obama declared: “2014 was the planet’s warmest year on record.”

This statement followed a joint press release from NOAA’s Karl and Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies, that said the same thing. The release was widely criticized for failing to point out that 2014 was in a statistical tie with several other recent years.

NOAA’s press release in June for Karl’s paper on the hiatus also appeared just before a big event: EPA was getting ready to issue its very controversial Clean Power Plan. And the politics are heating up even more with the approach of the United Nations Conference on Climate Change in Paris at the end of this month.

Last month, the House Science Committee, chaired by Lamar Smith (R-Texas), subpoenaed NOAA for data and communications relating to Karl’s article.  NOAA is refusing to give up the documents, citing confidentiality concerns and the integrity of the scientific process.

Rep. Eddie Bernice Johnson (D-Tex) called the request “a serious misuse of Congressional oversight powers.”

Is the subpoena harassment or appropriate constitutional oversight?

There are two legitimate concerns here.

The first is data quality, an issue that needs to be resolved owing to the central role that this data set is playing in U.S. climate policy.

The second issue is arguably more worrisome and difficult to uncover: a potential alliance between NOAA scientists and Obama administration officials that might be biasing and spinning climate science to support a political agenda.

Rep. Smith stated: “The American people have every right to be suspicious when NOAA alters data to get the politically correct results they want and then refuses to reveal how those decisions were made.”

The House Committee’s investigation should provide insight into the following questions that deserve answers.

To what extent did internal discussions occur about the more questionable choices made in adjusting the ocean temperature data?

Was any concern raised about the discrepancies of the new ocean temperature data set and NOAA’s other ocean temperature data set (OISST) that shows no warming since 2003?

Were any Obama administration officials communicating with NOAA about these statements prior to issuing press releases?

Was the release of the land and ocean temperature data sets, which were documented in papers previously published, delayed to follow Karl’s June press release?

Earlier this year, Rep. Raul Grijalva, D-Ariz., initiated an investigation into possible industry funding of scientists (including myself) who had recently provided Congressional testimony for the Republicans.

While potentially undisclosed industrial funding of research is a legitimate concern, climate science research funding from government is many orders of magnitude larger than industrial funding of such work.

If the House Science Committee can work to minimize the political influence on government-funded research, and also help to resolve legitimate scientific issues, it will have done both science and the policies that depend on science a big favor.

Judith Curry is professor and former chairwoman of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology. She is president of the Climate Forecast Applications Network. Follow Judith Curry on Twitter @curryja.