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Linearity of Outgoing Longwave Radiation: From an Atmospheric Column to Global Climate Models



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  • Journal Title:
    Geophysical Research Letters
  • Personal Author:
  • NOAA Program & Office:
  • Description:
    The linearity of global-mean outgoing longwave radiation (OLR) with surface temperature is a basic assumption in climate dynamics. This linearity manifests in global climate models, which robustly produce a global-mean longwave clear-sky (LWCS) feedback of 1.9 W/m2/K, consistent with idealized single-column models (Koll & Cronin, 2018, https//:doi.org/10.1073/pnas.1809868115). However, there is considerable spatial variability in the LWCS feedback, including negative values over tropical oceans (known as the “super-greenhouse effect”) which are compensated for by larger values in the subtropics/extratropics. Therefore, it is unclear how the idealized single-column results are relevant for the global-mean LWCS feedback in comprehensive climate models. Here we show with a simple analytical theory and model output that the compensation of this spatial variability to produce a robust global-mean feedback can be explained by two facts: (1) When conditioned upon free-tropospheric column relative humidity (RH), the LWCS feedback is independent of RH, and (2) the global histogram of free-tropospheric column RH is largely invariant under warming.
  • Keywords:
  • Source:
    Geophysical Research Letters, 47(11)
  • DOI:
  • Document Type:
    Journal Article
  • Funding:
    Grant no. NA18OAR4320123
  • Rights Information:
    Other
  • Compliance:
    Submitted
  • Main Document Checksum:
    urn:sha-512:24fa7d0543d8460625da50b508e95341ff5ea7cb2e61b8885234ed4f5b7b6b9e0fe9feb9731620ca535e96faa97976cb12ae84067fa336647c7a824818013d08
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  • File Type:
    Filetype[PDF - 4.05 MB ]
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