View larger. | Global fires detected in August 2018 in contrast to August 2019. The Sentinel-3 World Fire Atlas recorded 79,000 wildfires in August 2019, compared to just over 16,000 fires during the same period in 2018. Image via ESA.

Is Earth on fire? The European Space Agency was asking this question late last week (October 25, 2019), as multiple fires burned in Lebanon, in California, and elsewhere on the globe. Is Earth on fire, and, if it is, how do we know? How do scientists track earthly fires from one year to the next? How do they distinguish between a “normal” years for…