Megan C. Kirchmeier-Young and Xuebin Zhang

Proceedings of the National Academy of Sciences

Published date June 1, 2020

Human influence has intensified extreme precipitation in North America

Study key findings & significance

  • Although previous work has identified an anthropogenic influence on extreme precipitation at hemispheric scales, this study finds robust results for a continental scale. 
  • The study establishes that anthropogenic climate change has contributed to the intensification of continental and regional extreme precipitation. 
  • Furthermore, the study shows that the anthropogenic influence on North American regional precipitation will lead to more frequent and intense precipitation extremes in the future.

Author quotes

"We're finding that in North America, we have seen an increase in the frequency and severity of heavy rainfall events. And this is largely due to global warming," said Megan Kirchmeier-Young, a research scientist at Environment and Climate Change Canada and lead author of the study.


Precipitation extremes have implications for many facets of both the human and natural systems, predominantly through flooding events. Observations have demonstrated increasing trends in extreme precipitation in North America, and models and theory consistently suggest continued increases with future warming. Here, we address the question of whether observed changes in annual maximum 1- and 5-d precipitation can be attributed to human influence on the climate. Although attribution has been demonstrated for global and hemispheric scales, there are few results for continental and subcontinental scales. We utilize three large ensembles, including simulations from both a fully coupled Earth system model and a regional climate model. We use two different attribution approaches and find many qualitatively consistent results across different methods, different models, and different regional scales. We conclude that external forcing, dominated by human influence, has contributed to the increase in frequency and intensity of regional precipitation extremes in North America. If human emissions continue to increase, North America will see further increases in these extremes.