Effect of Baseline Period on Quantification of Climate Extremes Over the United States

• Published in: Geophysical research letters Vol. 50; no. 17
• Main Authors: Thomas, Natalie P., Collow, Allison B. Marquardt, Bosilovich, Michael G., Dezfuli, Amin
• Format: Journal Article
• Language: English
• Published: Goddard Space Flight Center American Geophysical Union 16-09-2023; John Wiley & Sons, Inc; Wiley
• Subjects: Air temperature; Climate; Climate and health; Climatic extremes; Climatic indexes; Climatology; Cold; Cold waves; Computation; Drought; Drought index; Earth Resources and Remote Sensing; Extreme cold; Extreme weather; Geosciences (General); Health risks; Heat waves; Heavy precipitation; Precipitation; Precipitation-temperature relationships; Regional variations; United States > US
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL105204

Extreme climate events are societally harmful and have increased in frequency and intensity in recent decades. Indices based on temperature and precipitation are a valuable way to quantify climate extremes. Certain indices are defined relative to percentiles, which are dependent on a climatological baseline period. In this study, indices computed using temperature and precipitation from the Modern Era Retrospective Analysis for Research and Applications, Version 2 are calculated using percentiles from three baseline periods: 1981–2010, 1991–2020 and 1981–2020. Updating the baseline period from 1981 to 2010 to 1991–2020 leads to significant changes in the quantification of temperature and precipitation extremes over the United States over 1980–2021. Using the later baseline period indicates more cold extremes, fewer warm extremes, and fewer but more intense precipitation extremes throughout the US, with regional variation. Changing the baseline period can mislead the public and decision makers, potentially undermining the appropriate response to climate-related health risks.