Substantial increase in concurrent droughts and heatwaves in the United States

Significance Climatic extremes cause significant damage to the environment and society, and can cause even more damage when multiple extremes occur simultaneously. This study shows that although there is no significant trend in meteorological drought, the concurrence of meteorological droughts and heatwaves shows statistically significant increases across the United States. We show that the tail of the distribution of concurrent drought and heatwave conditions has shifted toward more frequent and extreme concurrent extremes. Our study outlines a statistical approach for investigating continuous change in the cumulative distribution functions of climatic extremes. A combination of climate events (e.g., low precipitation and high temperatures) may cause a significant impact on the ecosystem and society, although individual events involved may not be severe extremes themselves. Analyzing historical changes in concurrent climate extremes is critical to preparing for and mitigating the negative effects of climatic change and variability. This study focuses on the changes in concurrences of heatwaves and meteorological droughts from 1960 to 2010. Despite an apparent hiatus in rising temperature and no significant trend in droughts, we show a substantial increase in concurrent droughts and heatwaves across most parts of the United States, and a statistically significant shift in the distribution of concurrent extremes. Although commonly used trend analysis methods do not show any trend in concurrent droughts and heatwaves, a unique statistical approach discussed in this study exhibits a statistically significant change in the distribution of the data.