The sensitivity of the hydrological cycle to internal climate variability versus anthropogenic climate change

Ryan J. Kramer, Brian J Soden

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

In response to rising CO2 concentrations, climate models predict that globally averaged precipitation will increase at a much slower rate than water vapor. However, some observational studies suggest that global-mean precipitation and water vapor have increased at similar rates. While the modeling results emphasize changes at multidecadal time scales where the anthropogenic signal dominates, the shorter observational record is more heavily influenced by internal variability. Whether the physical constraints on the hydrological cycle fundamentally differ between these time scales is investigated. The results of this study show that while global-mean precipitation is constrained by radiative cooling on both time scales, the effects of CO2 dominate on multidecadal time scales, acting to suppress the increase in radiative cooling with warming. This results in a smaller precipitation change compared to interannual time scales where the effects of CO2 forcing are small. It is also shown that intermodel spread in the response of atmospheric radiative cooling (and thus global-mean precipitation) to anthropogenically forced surface warming is dominated by clear-sky radiative processes and not clouds, while clouds dominate under internal variability. The findings indicate that the sensitivity of the global hydrological cycle to surface warming differs fundamentally between internal variability and anthropogenically forced changes and this has important implications for interpreting observations of the hydrological sensitivity.

Original languageEnglish (US)
Pages (from-to)3661-3673
Number of pages13
JournalJournal of Climate
Volume29
Issue number10
DOIs
StatePublished - Jan 1 2016

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Keywords

  • Anthropogenic effects
  • Climate sensitivity
  • Cloud radiative effects
  • Energy budget/balance
  • Hydrologic cycle
  • Latent heating/cooling
  • Physical meteorology and climatology

ASJC Scopus subject areas

  • Atmospheric Science

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