The threat of severe fires in California and western Oregon is increasing by 40-percent. A recent study by Oregon State University reports the increase is due in part to human-caused climate change, which includes atmospheric aerosols and carbon dioxide. Another factor causing the increase is strong, dry offshore winds. Linnia Hawkins, who led the study, says anthropogenic climate change has increased the likelihood of extreme hot, dry and windy weather in the fall, but has not necessarily increased the likelihood of fire. She added when CO2 and aerosols from human activity were included, the chance of extreme conditions was 40-percent higher in those areas of California and Oregon where recent fall fires have occurred.