%AYu, Zhongjie%AGriffis, Timothy%ABaker, John%BJournal Name: Communications Earth & Environment; Journal Volume: 2; Journal Issue: 1 %D2021%I %JJournal Name: Communications Earth & Environment; Journal Volume: 2; Journal Issue: 1 %K %MOSTI ID: 10314260 %PMedium: X %TWarming temperatures lead to reduced summer carbon sequestration in the U.S. Corn Belt %XAbstract The response of highly productive croplands at northern mid-latitudes to climate change is a primary source of uncertainty in the global carbon cycle, and a concern for future food production. We present a decadal time series (2007 to 2019) of hourly CO 2 concentration measured at a very tall tower in the United States Corn Belt. Analyses of this record, with other long-term data in the region, reveal that warming has had a positive impact on net CO 2 uptake during the early crop growth stage, but has reduced net CO 2 uptake in both croplands and natural ecosystems during the peak growing season. Future increase in summer temperature is projected to reduce annual CO 2 sequestration in the Corn Belt by 10–20%. These findings highlight the dynamic control of warming on cropland CO 2 exchange and crop yields and challenge the paradigm that warming will continue to favor CO 2 sequestration in northern mid-latitude ecosystems. %0Journal Article