Resetting tropospheric OH and CH4 lifetime with ultraviolet H2O absorption

• 成果类型: Article
• 署名作者: Prather, Michael J.; Zhu, Lei
• 署名单位: University of California System; University of California Irvine; State University of New York (SUNY) System; Wadsworth Center; State University of New York (SUNY) System; University at Albany, SUNY
• 刊物名称: SCIENCE
• ISSN/ISSBN: 0036-13449
• DOI: 10.1126/science.adn0415
• 发表日期: 2024-07-12
• 页码: 201-204
• 关键词: atmospheric chemistry; photolysis rates; hydroxyl; methane; climate; reactivity; impacts

摘要

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.