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Title: Resetting tropospheric OH and CH 4 lifetime with ultraviolet H 2 O absorption
The decay of methyl chloroform, a banned ozone-depleting substance, has provided a clear observational metric of mean tropospheric hydroxyl radical (OH) abundance. Almost all current global chemistry models calculate about 15% too much OH and thus too rapid methane loss. Methane is a short-lived climate forcer, critical to achieving global warming targets, and this error affects our model projections of climate change. New observations of water vapor absorption in the ultraviolet region (290 to 350 nanometers) imply reductions in sunlight with key photolysis rates decreasing by 8 to 12% in the near-surface tropical atmosphere. Incorporation of this new mechanism in a chemistry-transport model reduces OH and methane loss by only 4%, but combined with other proposed mechanisms, such as tropospheric halogen chemistry (7%), we may be able to resolve this conundrum.  more » « less
Award ID(s):
2135749
PAR ID:
10569664
Author(s) / Creator(s):
;
Publisher / Repository:
AAAS Science
Date Published:
Journal Name:
Science
Volume:
385
Issue:
6705
ISSN:
0036-8075
Page Range / eLocation ID:
201 to 204
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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