Solar cycle as a distinct line of evidence constraining Earth's transient climate response.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38114458.
- Also identified by DOI 10.1038/s41467-023-43583-7 and PMC identifier 10730699.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Severity of warming predicted by climate models depends on their Transient Climate Response (TCR). Inter-model spread of TCR has persisted at ~ 100% of its mean for decades. Existing observational constraints of TCR are based on observed historical warming response to historical forcing and their uncertainty spread is just as wide, mainly due to forcing uncertainty, and especially that of aerosols. Contrary, no aerosols are involved in solar-cycle forcing, providing an independent, tighter, constraint. Here, we define a climate sensitivity metric: time-dependent response regressed against time-dependent forcing, allowing phenomena with dissimilar time variations, such as the solar cycle with 11-year cyclic forcing, to be used to constrain TCR, which has a linear time-dependent forcing. We find a theoretical linear relationship between the two. The latest coupled atmosphere-ocean climate models obey the same linear relationship statistically. The proposed observational constraint on TCR is about [Formula: see text] as narrow as existing constraints. The central estimate, 2.2 <sup>o</sup>C, is at the midpoint of the spread of the latest generation of climate models, which are more sensitive than those of the previous generations.