Global temperature data from NASA show that April 2016 was the warmest April on record – despite satellites reporting that it was less warm than April 1998.
The analysis of global surface temperatures in April from the US space agency reports that last month was also the third warmest month recorded since records began in 1880. NASA reports that the average global temperature anomaly in April was +1.11oC, sharply down (0.18oC) on the +1.29oC reported in March and the record-breaking +1.33oC reported in February – the warmest month in the NASA data archive.
This decline indicates that global surface temperatures have begun to come off the boil with the fading of the El Niño Pacific Ocean warming event.
Variance to satellite measurements of global temperature
Separate analyses of global atmospheric temperature measurements collected from satellite instruments by Remote Sensing Systems and the University of Alabama in Huntsville both reported that April 2016 was the second warmest April in the history of satellite measurements which goes back to 1979 – with an anomaly slightly less than that reported in April 1998, when there was also a significant El Niño event. Both satellite data sets agree with the NASA data that February 2016 was the warmest month in their respective records.
However, NASA reports an anomaly of just 0.63oC for April 1998 (see data table reproduced below), significantly smaller than that seen last month and this difference between 1998 and 2016 that is larger than the uncertainty that is usually associated with such measurements.
The fact that the satellite data on global atmospheric temperatures reports that April this year was less warm than April 1998 while the NASA data on global surface temperatures shows that April this year was markedly warmer than April 1998 raises interesting questions about the differences in these two approaches to measuring global temperature and will rekindle criticism – particularly from climate sceptics – over changes made last year by NASA and by the US National Oceanic and Atmospheric Administration to the way they calculate the global temperature.
It is important to note that global surface temperature is not the same as global atmospheric temperature, that surface temperatures are measured on site while atmospheric temperatures are measured remotely by satellite, and that the reported anomalies are not directly comparable though the trends should be.
The NASA analysis for April shows that northern latitudes were particularly warm with temperatures that were above seasonal norms being reported in Alaska, northern Russia and the west of Greenland.
A comparison with the February data also shows that the tropical Pacific anomaly associated with El Niño is less intense.