Climate change is the leading factor in a rise in wildfires on the US west coast, found a study published by the Proceedings of the National Academy of Sciences (PNAS).

The study sought to analyze the impact of climate change caused by human activity on naturally-arid areas impacted by a rise in wildfires, such as California. Researchers discovered that man-made impact was 68%-88% likely to be the driving factor for atmospheric conditions fueling the wildfires, which have grown in frequency and severity.

Researchers tracked the levels of Vapor pressure deficit, or VPD, in the air in order to determine their hypothesis. VPD is defined as the difference between the amount of moisture in the air and how much moisture the air can hold when it is saturated. The higher the deficit, the more moisture the atmosphere absorbs from soil and plants, priming the landscape to burn. High levels of VPD mean that a specific climate is more prone to fires starting.