Identification

Title

Reactive halogens increase the global methane lifetime and radiative forcing in the 21st century

Abstract

CH4 is the most abundant reactive greenhouse gas and a complete understanding of its atmospheric fate is needed to formulate mitigation policies. Current chemistry-climate models tend to underestimate the lifetime of CH4, suggesting uncertainties in its sources and sinks. Reactive halogens substantially perturb the budget of tropospheric OH, the main CH4 loss. However, such an effect of atmospheric halogens is not considered in existing climate projections of CH4 burden and radiative forcing. Here, we demonstrate that reactive halogen chemistry increases the global CH4 lifetime by 6-9% during the 21st century. This effect arises from significant halogen-mediated decrease, mainly by iodine and bromine, in OH-driven CH4 loss that surpasses the direct Cl-induced CH4 sink. This increase in CH4 lifetime helps to reduce the gap between models and observations and results in a greater burden and radiative forcing during this century. The increase in CH4 burden due to halogens (up to 700 Tg or 8% by 2100) is equivalent to the observed atmospheric CH4 growth during the last three to four decades. Notably, the halogen-driven enhancement in CH4 radiative forcing is 0.05 W/m(2) at present and is projected to increase in the future (0.06 W/m(2) by 2100); such enhancement equals similar to 10% of present-day CH4 radiative forcing and one-third of N2O radiative forcing, the third-largest well-mixed greenhouse gas. Both direct (Cl-driven) and indirect (via OH) impacts of halogens should be included in future CH4 projections.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7gm8c1q

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2022-05-19T00:00:00Z

Frequency of update

Quality and validity

Lineage

Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact