Rep. Lamar Smith, chairman of the House Committee on Science, Space, and Technology, has made several inaccurate or misleading claims about climate science in an ongoing battle with the National Oceanic and Atmospheric Administration.

Smith, who has long rejected mainstream climate science, is using the committee’s subpoena power in an attempt to obtain internal communications at NOAA regarding a June study published in the journal Science. In his statements on this issue, Smith has claimed that “climate data has clearly showed [sic] no warming for the past two decades,” and that NOAA has “altered the data to get the results they needed to advance this administration’s extreme climate change agenda.”

In fact, there has been substantial warming over the past two decades, and NOAA’s adjustments to its data are well-studied, publicly available, peer-reviewed methods for obtaining the best possible temperature readings.

Has Warming Slowed?

At issue is a study led by NOAA scientist Thomas Karl. It is one of several recent peer-reviewed studies showing the so-called global warming “hiatus” (also known as the “pause” or “slowdown”) did not actually occur. Karl and his colleagues updated the global temperature data sets using the most up-to-date readings and analysis; this included more data from ocean buoys and from ship engine intake thermometers, and from an increasing number of land-based weather stations. They concluded: “Newly corrected and updated global surface temperature data … do not support the notion of a global warming ‘hiatus.'”

The other studies have come to similar conclusions.

Publishing in Climatic Change, a group of Stanford researchers led by Bala Rajaratnam wrote: “We find compelling evidence that recent claims of a ‘hiatus’ in global warming lack sound scientific basis.” Another group from universities in the U.K and Australia, as well has from Harvard, writing in the Bulletin of the American Meteorological Society, concluded: “We show that there are frequent fluctuations in the rate of warming around a longer-term warming trend, and that there is no evidence that identifies the recent period as unique or particularly unusual.”

According to a letter sent to Smith by Rep. Eddie Bernice Johnson of Texas, the ranking Democrat on the committee, Smith had previously requested information about Karl and NOAA’s research three separate times (on July 14, Sept. 10, and Sept. 25), before issuing the subpoena for internal communications on Oct. 13.

NOAA, which according to reporting by Nature has provided the publicly available data and has briefed the committee on the study, has refused the subpoena for internal communications. NOAA said that “confidentiality of these communications … is essential to frank discourse among scientists,” and noted that it is “a long-standing practice” to keep such communication confidential.

In a statement provided to Nature and Ars Technica, Smith accused NOAA of altering temperature data for political purposes:

Smith, Oct. 28: It was inconvenient for this administration that climate data has clearly showed no warming for the past two decades. 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. NOAA needs to come clean about why they altered the data to get the results they needed to advance this administration’s extreme climate change agenda. The agency has yet to identify any legal basis for withholding these documents. The Committee intends to use all tools at its disposal to undertake its Constitutionally-mandated oversight responsibilities.

He made similar claims in an email to us on Nov. 3. Smith is incorrect about the lack of warming, even before Karl’s and other studies debunked the notion of a hiatus — the global warming hiatus referred to a reduction in the rate of warming, rather than a lack of any warming whatsoever, according to the Intergovernmental Panel on Climate Change. In other words, the world was warming, only more slowly than in years prior. And again, the recent studies have shown that no such reduction in the rate of warming occurred; the planet has, in fact, continued to warm at about the same pace as previous decades.

Those who reject mainstream climate science often claim that there has been no warming specifically for 17 years, a claim that relies on cherry-picked data, as we have written about before. By starting with 1998, a particularly warm year, the amount of warming over that period appears smaller than starting with 1997 or 1999. The far more relevant long-term trend, however, is unequivocal; 14 of the 15 hottest years ever recorded have occurred this century, 2014 was likely the warmest year on record, and NOAA says 2015 is “extremely likely” to supplant it.

Satellites vs. Surface Data

In an email, Smith told us that satellite data in particular “has clearly showed [sic] no warming for the past two decades.” This is another common misrepresentation of the facts.

There are multiple satellite data sets of the temperature in the troposphere (the lowest atmospheric layer) — for example, from NOAA, from a research company called Remote Sensing Systems, and from a research group at the University of Alabama in Huntsville. The data sets disagree, and the last of those is the only one to show a lack of warming. Though there is some disagreement on the best ways to adjust and interpret satellite data, studies have indicated that correcting the UAH data in certain ways (specifically, removing a particular source of satellite error known as diurnal drift) would yield similar results to other data sets, indicating more warming.

Furthermore, even researchers who work on satellite temperature data say that the surface measurements used by NOAA and others are the more reliable data sets. Carl Mears, a senior research scientist at Remote Sensing Systems, told the Washington Post he would “trust the surface data a little more.”

Mears, March 24: All datasets contain errors. In this case, I would trust the surface data a little more because the difference between the long term trends in the various surface datasets (NOAA, NASA GISS, HADCRUT, Berkeley, etc) are closer to each other than the long term trends from the different satellite datasets. This suggests that the satellite datasets contain more “structural uncertainty” than the surface dataset.

“Structural uncertainty” refers to the level of confidence that scientists have in the tools and calculations used to arrive at their conclusions. There is more of this uncertainty with the satellite data than with the surface temperature measurements.

Smith also told us that “[r]eanalysis data sets from the numerical weather prediction centers, both NOAA and the European ECMWF, also clearly show a surface temperature warming hiatus.” Reanalysis is a specific type of climate data analysis. The European Center for Medium-Range Weather Forecasts does do this type of analysis, but Smith is incorrect about its findings. In an email, an ECMWF spokeswoman, Silke Zollinger, told us that its data “shows substantial variations between years in global-mean surface air temperature, but no persistent hiatus in global warming.” We have asked NOAA if its “reanalysis” data sets show a hiatus, and will update this post if we hear back.

As for NOAA’s alteration of data, Smith again misunderstands the science. As we have written before, temperature data often require adjustment in order to paint the most accurate picture of the global climate. The methodology behind the recent updates and adjustments is publicly available, and the published studies were peer-reviewed.

Committee Subpoena Controversy

Smith defended his use of subpoena in an email to us:

Smith, Nov. 3: Despite what some critics claim, the subpoena is not only about scientists. Political operatives and other NOAA employees likely played a large role in approving NOAA’s decision to adjust data that allegedly refutes the hiatus in warming… The Committee needs to understand the full context of NOAA’s decision-making process.

He also claimed that NOAA “conveniently” timed the news release on Karl’s study to coincide with the Obama administration’s announcement of “its extensive climate change regulations.” That’s speculation. Though the White House is engaged in a number of climate change-related efforts, the most significant regulation issued recently is the Clean Power Plan, designed to lower emissions from power plants. The NOAA news release in question was on June 4; the unveiling of the final Clean Power Plan by Obama was on Aug. 3, though the plan was proposed and under discussion for more than a year before that.

A spokeswoman for NOAA, Ciaran Clayton, defended the subpoena refusal to Nature: “We stand behind our scientists, who conduct their work in an objective manner. We have provided all of the information the Committee needs to understand this issue.”

In her letter to Smith, Johnson accused him and the committee of creating a “baseless conflict.” She wrote:

Johnson, Oct. 23: By issuing this subpoena, you have instigated a Constitutional conflict with an inquiry that seems more designed to harass climate scientists than to further any legitimate legislative purpose. This is a serious misuse of Congressional oversight powers.

The committee’s rules on issuing subpoenas were changed in January, over the objections of the Democratic members. Previously, consent of the ranking member was required, but the changes gave unilateral subpoena power to the committee chairman. Johnson also noted that the committee under Smith’s leadership has issued six subpoenas, more than were used in its previous 54-year history.

We have found Smith cherry-picking data before that supports his claims regarding climate science. In this case again, there is no scientific basis for his claims.

Editor’s Note: SciCheck is made possible by a grant from the Stanton Foundation.