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Title: Empirical evidence for a recent slowdown in irrigation-induced cooling

Abstract

Understanding the influence of past land use changes on climate is needed to improve regional projections of future climate change and inform debates about the tradeoffs associated with land use decisions. The effects of rapid expansion of irrigated area in the 20th century has remained unclear relative to other land use changes, such as urbanization, that affected a similar total land area. Using spatial and temporal variations in temperature and irrigation extent observed in California, we show that irrigation expansion has had a large cooling effect on summertime average daily daytime temperatures (-0.15 to -0.25 C.decade{sup -1}), which corresponds to a cooling estimated at -2.0 - -3.3 C since the introduction of irrigation practice. Irrigation has negligible effects on nighttime temperatures, leading to a net cooling effect of irrigation on climate (-0.06 to -0.19 C.decade{sup -1}). Stabilization of irrigated area has occurred in California since 1980 and is expected in the near future for most irrigated regions. The suppression of past human-induced greenhouse warming by increased irrigation is therefore likely to slow in the future, and a potential decrease in irrigation may even contribute to a more rapid warming. Changes in irrigation alone are not expected to influence broadscale temperatures,more » but they may introduce large uncertainties in climate projections for irrigated agricultural regions, which provide roughly 40% of global food production.« less

Authors:
;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
940480
Report Number(s):
UCRL-JRNL-229604
TRN: US200824%%43
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Resource Relation:
Journal Name: Proceedings of the National Academy of Sciences, vol. 104, no. 34, August 21, 2007, pp. 13582-13587; Journal Volume: 104; Journal Issue: 34
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; CALIFORNIA; CLIMATES; FOOD; GREENHOUSE GASES; IRRIGATION; LAND USE; PRODUCTION; STABILIZATION

Citation Formats

Bonfils, C, and Lobell, D. Empirical evidence for a recent slowdown in irrigation-induced cooling. United States: N. p., 2007. Web. doi:10.1073/pnas.0700144104.
Bonfils, C, & Lobell, D. Empirical evidence for a recent slowdown in irrigation-induced cooling. United States. doi:10.1073/pnas.0700144104.
Bonfils, C, and Lobell, D. Fri . "Empirical evidence for a recent slowdown in irrigation-induced cooling". United States. doi:10.1073/pnas.0700144104. https://www.osti.gov/servlets/purl/940480.
@article{osti_940480,
title = {Empirical evidence for a recent slowdown in irrigation-induced cooling},
author = {Bonfils, C and Lobell, D},
abstractNote = {Understanding the influence of past land use changes on climate is needed to improve regional projections of future climate change and inform debates about the tradeoffs associated with land use decisions. The effects of rapid expansion of irrigated area in the 20th century has remained unclear relative to other land use changes, such as urbanization, that affected a similar total land area. Using spatial and temporal variations in temperature and irrigation extent observed in California, we show that irrigation expansion has had a large cooling effect on summertime average daily daytime temperatures (-0.15 to -0.25 C.decade{sup -1}), which corresponds to a cooling estimated at -2.0 - -3.3 C since the introduction of irrigation practice. Irrigation has negligible effects on nighttime temperatures, leading to a net cooling effect of irrigation on climate (-0.06 to -0.19 C.decade{sup -1}). Stabilization of irrigated area has occurred in California since 1980 and is expected in the near future for most irrigated regions. The suppression of past human-induced greenhouse warming by increased irrigation is therefore likely to slow in the future, and a potential decrease in irrigation may even contribute to a more rapid warming. Changes in irrigation alone are not expected to influence broadscale temperatures, but they may introduce large uncertainties in climate projections for irrigated agricultural regions, which provide roughly 40% of global food production.},
doi = {10.1073/pnas.0700144104},
journal = {Proceedings of the National Academy of Sciences, vol. 104, no. 34, August 21, 2007, pp. 13582-13587},
number = 34,
volume = 104,
place = {United States},
year = {Fri Jan 19 00:00:00 EST 2007},
month = {Fri Jan 19 00:00:00 EST 2007}
}