Scientists, University of California at Los Angeles and the Lawrence Livermore National Laboratory confirmed the link between climate change and the increase of land areas affected by large forest fires. This was reported in an article published in the journal Proceedings of the National Academy of Sciences.
For 17 years, from 1984 to 2000, the average burnt area in the 11 western states was 683 000 hectares per year. Over the next 17 years, until 2018, the average area of the burn was about 1.35 million hectares per year. And in 2020, according to the report of the National inter-agency focal point, the amount of land devastated by forest fires in the west, reached 3.5 million hectares.
To determine the cause, the researchers used artificial intelligence, which analyzed data on climate and fires. It revealed the role of the key factors contributing to fire – vapor pressure deficit. This parameter indicates the difference between the theoretical vapor pressure in the saturated air (humidity of one hundred per cent) and the actual water vapor pressure retained in air at the same temperature. At high vapor pressure deficit of the air absorbs more moisture from the soil and plants.
The study found that 68 percent of the total increase in vapor pressure deficit in the western United States between 1979 and 2020, probably due to global warming caused by human activities. The remaining 32 percent due to natural causes. Thus, climate change induced by human activity, is the main cause of increase in the number of fires in the western United States.