Parts of the western United States and Mexico, Brazil, and East Africa now face wildfire seasons that are more than a month longer than they were 35 years ago. The longer season in the western United States is attributed to changes in the timing of snowmelt, vapor pressure, and the timing of spring rains — all of which have been linked to global warming and climate change.
Overall, 54 percent of the world’s vegetated surfaces experienced long fire weather seasons more frequently between 1996 and 2013 as compared with 1979-1996, according to Jolly. This amounted to a doubling in the total global burnable area affected by long fire weather seasons. (For this calculation, “long fire season” was defined as a length that was one standard deviation above the historical mean.)
It is important to note that although the study shows many environments have become more prone to fires, it does not demonstrate that the wildfires burned more intensely or charred more acres. That’s because even with longer and more frequent fire seasons, other factors can affect whether fires occur and how they behave, such as: whether lightning or human activity ignites the fires; whether humans attempt to suppress them; and whether there is enough fuel to sustain them.