Cornwall Alliance Research Associate for Developing Countries Vijay Jayaraj recently wrote “Four Reasons Alarmists Are Wrong on Climate Change,” which we sent out in our email newsletter. We often receive emails regarding these newsletters, and always try to provide a response. One of the emails about Vijay’s article led to Dr. Beisner writing a response about global temperatures that helps to answer some common questions.

The original email simply said, “See attached article for an accurate report on world temperatures.”

The attached article, titled “While the U.S. shivered, the rest of the world simmered in planet’s third-hottest April,” was from the Washington Post.

Dr. Beisner responded:

Dear ______,

Thank you for your email. The source of data for the article you sent, the European Centre for Medium-Range Weather Forecast, reports land and sea surface data. The number of surface temperature monitors is, in reference to the total area of the globe, very small, and their locations are biased toward built-up, low-altitude, and low-latitude areas, resulting in significant upward bias of temperature readings because of the “urban heat island” (UHI) effect and the comparative warmth of low versus high altitudes and low versus high latitudes.

The most credible source of global temperature not just for the surface but for the lower mid-troposphere (the bulk of the atmosphere) is readings from NASA satellites. Among other differences between these and the surface data, two are especially important reasons why they’re more credible. First, they’re truly global and spatially representative, and second, they’re not contaminated by UHI. Drs. John Christy and Roy Spencer (the latter a Senior Fellow of the Cornwall Alliance), of the University of Alabama at Hunstville (UAH), maintain this database and report it monthly. Their most recent report (May 1, 2018) lists the global mid-tropospheric temperature anomaly for April as +0.21 C˚ above the 1981–2010 mean for April; the northern hemisphere was 0.31 C˚ above that mean, the southern hemisphere 0.10 C˚ above it, and the tropics actually 0.13 C˚ below it. The full data are here, and here’s a graph of the satellite global temperature data from Dr. Spencer’s report of it:

The UAH satellite data show that for the globe as a whole, April 2018 was the 7^th-warmest April in the satellite record (1979–present), not the 3^rd-warmest as the ECMWF’s surface-only data indicated, and the satellite data showed April 0.21 C˚ above the 1981–2010 mean, less than 1/4^th as high as the ECMWF surface-only data’s 0.9 C˚ above the mean. The margin of error for the global satellite temperature measurements is roughly 0.1 C˚. That makes April 2018’s anomaly of 0.21 C˚ statistically indistinguishable from that of 2017 (0.27), 2002 (0.23), 2001 (0.2), 2003 (0.15), 1995, 2004, and 2007 (all 0.14), and 2012 and 2014 (both 0.11)—the 5^th through 14^th warmest of the 40 Aprils during the satellite record period (1979–present). I.e., so far as statistical significance, April 2018 could have been anywhere from the 5^th to the 14^th-warmest of the period. The same dataset shows April of 1998 as 0.74 C˚ above the 1981–2010 mean (the warmest—20 years ago!), more than three times April 2018’s anomaly, and April 2016 as 0.72 C˚ above the mean, almost exactly three times April 2018’s anomaly. (The April temperature anomaly in the satellite record for every year from 1979–2018, ranked from highest to lowest, is in the spreadsheet below.)

The satellite data show a decadal warming trend 1979–present for the globe as a whole of 0.13 C˚, which is a little more than 1/4^th lower than the ECMWF’s surface-only data’s decadal trend of 0.18 C˚. The average decadal warming trend for the same period simulated by the CMIP-5 (Coupled Model Intercomparison Project, 5^th generation) climate models on which the UN Intergovernmental Panel on Climate Change relies is approximately +0.216 C˚. I.e., the UAH observed decadal trend is 40% lower, and the ECMWF’s observed decadal trend is 17% lower, than the models’ predictions. Both the UAH data and the ECMWF data, therefore, call seriously into question the primary basis for predictions of dangerous anthropogenic global warming.

April Satellite Temperature Anomaly (difference from 1981–2010 average, in Celsius), 1979–2018

1998	0.74
2016	0.72
2005	0.33
2010	0.33
2017	0.27
2002	0.23
2018	0.21
2001	0.2
2003	0.15
1995	0.14
2004	0.14
2007	0.14
2012	0.11
2014	0.11
1988	0.09
2015	0.09
1983	0.08
1987	0.08
2006	0.07
2000	0.05
2013	0.05
1980	0.03
1999	0.01
1991	-0.01
2009	-0.01
2011	-0.03
1990	-0.08
1996	-0.08
1981	-0.13
2008	-0.13
1994	-0.15
1986	-0.16
1989	-0.2
1984	-0.25
1997	-0.26
1992	-0.27
1979	-0.28
1985	-0.31
1982	-0.32
1993	-0.34

Some other things to keep in mind as you ponder the Washington Post report on the ECMWF data: Its headline, “While the U.S. shivered, the rest of the world simmered in the planet’s third-hottest April” was quite misleading, even compared with the actual text of the article. The article included a graphic of Ryan Maue’s Tweet that for the lower 48 states April 28 was “more than 3˚F [1.7 ˚C] below the last 30-years average,” but that difference—between 48.5˚F and 51.5˚F—is hardly remarkable and not likely to make the difference between comfort and shivering; most locales around the world experience five to ten times that much temperature difference between nighttime low and daytime high on any given day and ten to twenty times that much between winter low and summer high. Is such a temperature difference really a crisis? And the ECMWF’s global temperature anomaly for April of 0.18 C˚ (0.324 F˚) is so small that people’s skin wouldn’t detect it—hardly a reason for the word simmered. Do you see how the headline manipulates perception to be far more sensational than the data justify?

Thanks again for writing.

—Cal

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