Some heated claims were made in a recently published scientific paper, “Recent Global Warming as Confirmed by AIRS,” authored by Susskind et al. One of the co-authors is NASA’s Dr. Gavin Schmidt, keeper of the world’s most widely used dataset on global warming: NASA GISTEMP
Press coverage for the paper was strong. ScienceDaily said that the study “verified global warming trends.” U.S. News and World Report’s headline read, “NASA Study Confirms Global Warming Trends.” A Washington Post headline read, “Satellite confirms key NASA temperature data: The planet is warming — and fast,” with the author of the article adding, “New evidence suggests one of the most important climate change data sets is getting the right answer.”
The new paper uses the AIRS remote sensing instrument on NASA’s Aqua satellite. The study describes a 15-year dataset of global surface temperatures from that satellite sensor. The temperature trend value derived from that data is +0.24 degrees Centigrade per decade, coming out on top as the warmest of climate analyses.
Oddly, the study didn’t compare two other long-standing satellite datasets from the Remote Sensing Systems (RSS) and the University of Alabama at Huntsville (UAH). That’s an indication of the personal bias of co-author Schmidt, who in the past has repeatedly maligned the UAH dataset and its authors because their findings didn’t agree with his own GISTEMP dataset. In fact, Schmidt’s bias was so strong that when invited to appear on national television to discuss warming trends, in a fit of spite, he refused to appear at the same time as the co-author of the UAH dataset, Dr. Roy Spencer.
A breakdown of several climate datasets, appearing below in degrees centigrade per decade, indicates there are significant discrepancies in estimated climate trends:
- AIRS: +0.24 (from the 2019 Susskind et al. study)
- GISTEMP: +0.22
- ECMWF: +0.20
- RSS LT: +0.20
- Cowtan & Way: +0.19
- UAH LT: +0.18
- HadCRUT4: +0.17
Which climate dataset is the right one? Interestingly, the HadCRUT4 dataset, which is managed by a team in the United Kingdom, uses most of the same data GISTEMP uses from the National Oceanic and Atmospheric Administration’s Global Historical Climate Network. Among the major datasets, HadCRUT4 shows the lowest temperature increase, one that’s nearly identical to UAH.
Critics of NASA’s GISTEMP have long said its higher temperature trend is due to scientists applying their own “special sauce” at the NASA Goddard Institute for Space Studies (GISS), where Schmidt is head of the climate division. But what is even more suspect is the fact that while this is the first time Schmidt has dared to compare his overheated GISTEMP dataset to a satellite dataset, he chose the AIRS data, which has only 15 years’ worth of data, whereas RSS and UAH have 30 years of data. Furthermore, Schmidt’s use of a 15-year dataset conflicts with the standard practices of the World Meteorological Organization, which states “as the statistical description in terms of the mean and variability of relevant quantities over a period of time… The classical period is 30 years…”
Why would Schmidt, who bills himself as a professional climatologist, break with the standard 30-year period? It appears he did it because he knew he could get an answer he liked, one that’s close to his own dataset, thus “confirming” it.
The 15-year period in this new study is too short to say much of anything of value about global warming trends, especially since there was a record-setting warm El Niño near the end of that period in 2015 and 2016. The El Niño event in the Pacific allowed warm water heated by the Sun to collect, dispersing heat into the atmosphere and thus warming the planet. Greenhouse gas induced “climate change” had nothing to do with it; it was a natural heating process that has been going on for millennia.
Figure 1: At left, Panel A NOAA sea surface temperature data showing peaking of the 2015/2016 El Niño event in the equatorial Pacific Ocean. Panel B is Figure 1 from Susskind et al. 2019 with annotations added to illustrate correlation with the peak of the 2015-16 El Niño event in AIRS data.
As you can see in Figure 1 above, there has been rapid cooling from that El Niño-induced peak in 2016, and the global temperature is now approaching what it was before the event. Had there not been an El Niño event in 2015 and 2016, creating a spike in global temperature, it is likely Schmidt wouldn’t get a “confirming” answer for a 15-year temperature trend. As you can see in the figure above on Panel B, the peak occurred in early 2016, and the data trend before that was essentially flat.
It appears that the authors of the Susskind et al. paper were motivated by timing and opportunity. It was crafted to advance an agenda, not climate science.
Anthony Watts is a senior fellow for environment and climate at The Heartland Institute.