Florian E. Roemer, Stefan A. Buehler, Lukas Kluft, Robert Pincus
{"title":"Effect of Uncertainty in Water Vapor Continuum Absorption on CO2 Forcing, Longwave Feedback, and Climate Sensitivity","authors":"Florian E. Roemer, Stefan A. Buehler, Lukas Kluft, Robert Pincus","doi":"10.1029/2023MS004157","DOIUrl":null,"url":null,"abstract":"<p>We investigate the effect of uncertainty in water vapor continuum absorption at terrestrial wavenumbers on CO<sub>2</sub> forcing <span></span><math>\n <semantics>\n <mrow>\n <mi>F</mi>\n </mrow>\n <annotation> $\\mathcal{F}$</annotation>\n </semantics></math>, longwave feedback <i>λ</i>, and climate sensitivity <span></span><math>\n <semantics>\n <mrow>\n <mi>S</mi>\n </mrow>\n <annotation> $\\mathcal{S}$</annotation>\n </semantics></math> at surface temperatures <i>T</i><sub>s</sub> between 270 and 330 K. We calculate this uncertainty using a line-by-line radiative-transfer model and a single-column atmospheric model, assuming a moist-adiabatic temperature lapse-rate and 80% relative humidity in the troposphere, an isothermal stratosphere, and clear skies. Due to the lack of a comprehensive model of continuum uncertainty, we represent continuum uncertainty in two different idealized approaches: In the first, we assume that the total continuum absorption is constrained at reference conditions; in the second, we assume that the total continuum absorption is constrained for all atmospheres in our model. In both approaches, we decrease the self continuum by 10% and adjust the foreign continuum accordingly. We find that continuum uncertainty mainly affects <span></span><math>\n <semantics>\n <mrow>\n <mi>S</mi>\n </mrow>\n <annotation> $\\mathcal{S}$</annotation>\n </semantics></math> through its effect on <i>λ</i>. In the first approach, continuum uncertainty mainly affects <i>λ</i> through a decrease in the total continuum absorption with <i>T</i><sub>s</sub>; in the second approach, continuum uncertainty affects <i>λ</i> through a vertical redistribution of continuum absorption. In both experiments, the effect of continuum uncertainty on <span></span><math>\n <semantics>\n <mrow>\n <mi>S</mi>\n </mrow>\n <annotation> $\\mathcal{S}$</annotation>\n </semantics></math> is modest at <i>T</i><sub>s</sub> = 288 K (≈0.02 K) but substantial at <i>T</i><sub>s</sub> ≥ 300 K (up to 0.2 K), because at high <i>T</i><sub>s</sub>, the effects of decreasing the self continuum and increasing the foreign continuum have the same sign. These results highlight the importance of a correct partitioning between self and foreign continuum to accurately determine the temperature dependence of Earth's climate sensitivity.</p>","PeriodicalId":14881,"journal":{"name":"Journal of Advances in Modeling Earth Systems","volume":null,"pages":null},"PeriodicalIF":4.4000,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023MS004157","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Advances in Modeling Earth Systems","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1029/2023MS004157","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"METEOROLOGY & ATMOSPHERIC SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
We investigate the effect of uncertainty in water vapor continuum absorption at terrestrial wavenumbers on CO2 forcing , longwave feedback λ, and climate sensitivity at surface temperatures Ts between 270 and 330 K. We calculate this uncertainty using a line-by-line radiative-transfer model and a single-column atmospheric model, assuming a moist-adiabatic temperature lapse-rate and 80% relative humidity in the troposphere, an isothermal stratosphere, and clear skies. Due to the lack of a comprehensive model of continuum uncertainty, we represent continuum uncertainty in two different idealized approaches: In the first, we assume that the total continuum absorption is constrained at reference conditions; in the second, we assume that the total continuum absorption is constrained for all atmospheres in our model. In both approaches, we decrease the self continuum by 10% and adjust the foreign continuum accordingly. We find that continuum uncertainty mainly affects through its effect on λ. In the first approach, continuum uncertainty mainly affects λ through a decrease in the total continuum absorption with Ts; in the second approach, continuum uncertainty affects λ through a vertical redistribution of continuum absorption. In both experiments, the effect of continuum uncertainty on is modest at Ts = 288 K (≈0.02 K) but substantial at Ts ≥ 300 K (up to 0.2 K), because at high Ts, the effects of decreasing the self continuum and increasing the foreign continuum have the same sign. These results highlight the importance of a correct partitioning between self and foreign continuum to accurately determine the temperature dependence of Earth's climate sensitivity.
期刊介绍:
The Journal of Advances in Modeling Earth Systems (JAMES) is committed to advancing the science of Earth systems modeling by offering high-quality scientific research through online availability and open access licensing. JAMES invites authors and readers from the international Earth systems modeling community.
Open access. Articles are available free of charge for everyone with Internet access to view and download.
Formal peer review.
Supplemental material, such as code samples, images, and visualizations, is published at no additional charge.
No additional charge for color figures.
Modest page charges to cover production costs.
Articles published in high-quality full text PDF, HTML, and XML.
Internal and external reference linking, DOI registration, and forward linking via CrossRef.