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Abstract. Recent analyses show the importance of methane shortwave absorption, which many climate models lack. In particular, Allen et al. (2023) used idealized climate model simulations to show that methane shortwave absorption mutes up to 30 % of the surface warming and 60 % of the precipitation increase associated with its longwave radiative effects. Here, we explicitly quantify the radiative and climate impacts due to shortwave absorption of the present-day methane perturbation. Our results corroborate the hypothesis that present-day methane shortwave absorption mutes the warming effects of longwave absorption. For example, the global mean cooling in response to the present-day methane shortwave absorption is -0.10±0.07 K, which offsets 28 % (7 %–55 %) of the surface warming associated with present-day methane longwave radiative effects. The precipitation increase associated with the longwave radiative effects of the present-day methane perturbation (0.012±0.006 mm d−1) is also muted by shortwave absorption but not significantly so (-0.008±0.009 mm d−1). The unique responses to methane shortwave absorption are related to its negative top-of-the-atmosphere effective radiative forcing but positive atmospheric heating and in part to methane's distinctive vertical atmospheric solar heating profile. We also find that the present-day methane shortwave radiative effects, relative to its longwave radiative effects, are about 5 times larger than those under idealized carbon dioxide perturbations. Additional analyses show consistent but non-significant differences between the longwave versus shortwave radiative effects for both methane and carbon dioxide, including a stronger (negative) climate feedback when shortwave radiative effects are included (particularly for methane). We conclude by reiterating that methane remains a potent greenhouse gas.
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This content will become publicly available on May 9, 2026
A spectroscopic theory for how mean rainfall changes with surface temperature
Surface warming is projected to increase global mean rainfall primarily by increasing the radiative cooling of the atmosphere. However, the radiative mechanisms which cause cooling to increase are not well understood. Here, we show that changes in cooling are driven primarily by changes in atmospheric opacity, particularly within the water vapor window. This suggests that changes in mean rainfall are primarily controlled by the thermodynamic and spectroscopic properties of Earth’s main greenhouse gases: water vapor and carbon dioxide. Consistent with comprehensive general circulation models, our results explain why mean rainfall increases with surface warming at about 2% per kelvin, why this rate is largely unchanged over numerous doublings of atmospheric carbon dioxide, and why mean rainfall decreases in hothouse climates.
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- Award ID(s):
- 1916908
- PAR ID:
- 10643754
- Publisher / Repository:
- American Association for the Advancement of Science
- Date Published:
- Journal Name:
- Science Advances
- Volume:
- 11
- Issue:
- 19
- ISSN:
- 2375-2548
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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