NASA Confirms Global Warming Trends, Says 2015, 2016 and 2017 Were Hottest on Record

To tackle global warming, we need to accurately know the scale of the problem that we are dealing with. As part of this effort, a team of NASA scientists set out to verify the accuracy of recent global warming figures that suggest, among other things, that 2015, 2016 and 2017 were the hottest years on record.

For the research in the study, published in the journal Environmental Research Letters, scientists took measurements of the Earth's surface temperature in different regions using a satellite-based infrared technology known as the Atmospheric Infra-Red Sounder (AIRS) between the years 2003 and 2017.

They then compared these measurements to data on the air temperature 2 meters above the surface collected by weather stations around the world and analyzed by NASA's Goddard Institute for Space Studies Surface Temperature Analysis.

Their results showed that the two data sets were highly consistent, thus verifying that they are accurate. To understand the significance of these findings, Newsweek spoke to the Goddard Institute's Gavin Schmidt, one of the authors of the study.

Why did you decide to conduct this study? Why is this kind of verification important?
The most important issue in science today is being able to independently replicate important results, and this is even more critical for science issues of great public importance. For climate change, although we have a host of independent indications that the planet is warming—from observations of ice melt, ecosystems shift, sea level rise, etc.—it has been hard to quantifiably verify the magnitude and pattern of surface warming trends seen in the analyses of weather station and ocean ship data.

There are many groups that have independently analyzed that data—NASA, the Goddard Institute and the U.K. Met Office among them—and shown that results are consistent. But this is the first time that we have used a near globally complete satellite data set to evaluate and confirm the surface temperature [data.]

There have, of course, been other satellite data used to compare to the surface warming, but these instruments measure temperatures high above the surface and are expected to differ in multiple ways. The AIRS ground temperature anomalies used here are also not exactly the same things that weather stations measure—which is 2-meter air temperature—but are much closer and, as can be seen in the paper, show a pattern of warming at the month-to-month, through to the decadal, scales that are remarkably consistent.

What were your key findings?
The satellite data and the weather station-based [data] are extremely well correlated over most of the globe and over time. Where there are differences we can understand the issues—for instance, during a satellite outage in November 2003, the correlations drop. In areas with poor station data coverage—for example, central Africa and the southern high latitudes—we see a similar lack of coherence. Additionally, we see that in some places the AIRS data suggests greater warming than has been generally reported.

What are the implications of these findings? Why are they significant?
Not only is this a further confirmation that the world is warming over the last two decades—which really isn't needed—but it is an independent confirmation that the magnitudes of the assessed changes are accurate and possibly even a little underestimated. This is a clear demonstration of the utility of the multiple views of the Earth enabled by NASA science.

Do you think findings such as these can go any way to addressing the issue of climate change skepticism?
Well, since most climate skepticism has nothing much to do with facts, demonstrating that those facts are robust probably won't make a dent. However, it is a good data point for people who might have genuine questions about how accurate the global warming trends are.

In your view, what are the biggest challenges we face when it comes to addressing climate change?
The key challenge in my opinion—not speaking for NASA or my co-authors—remains making big enough dents in our carbon emissions. There are a few good ideas and shifts happening—getting off coal, electric vehicles, renewables—but it isn't anywhere near large enough to get close to stabilizing the climate, which needs around 80 percent cuts within a few decades, going to near 100 percent cuts by 2100.

It's easy to talk about targets but harder to translate that into actions that are both sustainable, commensurate with the size of the problem and provide other benefits that people want—like cleaner air, more livable cities, clean jobs, etc. Some people seem to be rising to the challenge, but not yet enough.