A new analysis of 35 years of meteorological data confirms fire seasons have become longer. Fire season, which varies in timing and duration based on location, is defined as the time of year when wildfires are most likely to ignite, spread, and affect resources.
In the map above, areas where the fire season lengthened between 1979 and 2014 are shown with shades of orange and red. Areas where the length of the fire season stayed the same are yellow. Shades of blue show where the fire season grew shorter. Gray indicates that there was not enough vegetation to sustain wildfires.
The researchers found that fire weather seasons have lengthened across one quarter of Earth’s vegetated surface. In certain areas, extending the fire season by a bit each year added up to a large change over the full study period. For instance, 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 authors attribute the longer season in the western United States 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.
In some parts of the world, tough fire seasons have also become more frequent. “The map at the top of the page depicts steady trends in season length, while the map below shows changes in variability,” explained Jolly. “In other words, the map below shows where long seasons are becoming more frequent, even if they aren’t becoming steadily longer.”
NOTE: This analysis was done five years ago.