NASA researchers say that recent global warming figures are accurate, although they may be underestimating temperature changes in the Arctic.
By drawing on data from a satellite-based infrared measurement system of surface temperatures called AIRS (Atmospheric Infra-Red Sounder) from 2003 to 2017, NASA researchers were able to verify the accuracy of recent global warming figures recorded on the ground.
“Both data sets demonstrate the earth’s surface has been warming globally over this period, and that 2016, 2017, and 2015 have been the warmest years in the instrumental record, in that order,” says lead author Dr. Joel Susskind from NASA’s Goddard Space Flight Center.
The team compared AIRS data to surface air temperature anomalies recorded in various stations on the ground — principally the Goddard Institute for Space Studies Surface Temperature Analysis (GISTEMP). All in all, the two datasets show a very high level of consistency over the last 15 years, the authors report. AIRS data reflects skin temperature at the surface of the ocean, land, and snow/ice covered regions. Surface-based data are a blend of two-meter surface air data anomalies over land, and bulk sea surface temperature anomalies in the ocean.
“AIRS data complement GISTEMP because they are at a higher spatial resolution than GISTEMP, and have more complete global coverage,” Susskind explains.
Our estimates of global and regional temperature change are constructed primarily from surface temperature data. However, this dataset is imperfect. Things like data recording gaps, changes to instruments or practices at various stations, station relocation, and localized effects such as the urban heat island effect all impact on the integrity and reliability of ground-recorded data. The team set out to verify whether we handle these imperfections the right way or not — in other words, whether we weed out their effects or let them skew our results.
To make the comparison, the team constructed grid-point climatologies for each calendar month for each set of data by averaging monthly values from 2003 to 2017. They defined anomalies for any given month in a certain year as the difference of the grid point value for that month from its monthly climatology. The two sets of data fit very well, the team reports. However, they do note that the “findings revealed that the surface-based data sets may be underestimating the temperature changes in the Arctic”, according to co-author Dr. Gavin Schmidt from NASA’s Goddard Institute for Space Studies.
“This means the warming taking place at the poles may be happening more quickly than previously thought,” he adds.
All in all, the findings are quite encouraging — in that our previous estimates in regard to climate change weren’t wrong; they’re still very worrying, however. The findings should help further refine our climate models in regards to the Arctic, while also boosting the trustworthiness of other climate estimates based on ground data. Furthermore, the paper also offers us the possibility to improve on ground-recorded data.
“Our work also shows that complementary satellite-based surface temperature analyses serve as an important validation of surface-based estimates. They may point the way to make improvements in surface-based products that can perhaps be extended back many decades.”
The paper “Recent Global Warming as Confirmed by AIRS” has been published in the journal Environmental Research Letters.