Early Earth's climate

Cloud feedback from reduced land fraction and ozone concentrations

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Two features of early Earth—reduced ozone (O3) concentration and land fraction are investigated with a general circulation model (GCM). These features are components of a paradox (Faint‐Young Sun paradox) which has intrigued researchers for more than two decades. In this study, land fraction and O3 concentrations are uniformly reduced by 100 percent. The reduction in O3 takes place in the troposphere and stratosphere with all other variables held constant including present‐day land fraction. Two sensitivity tests under global ocean conditions are reported: one case with implied oceanic poleward transports of heat, the other case with no implied oceanic poleward transports of heat. The results show that the removal of land under present‐day conditions increases cloud fractions and cool surface temperatures, unless heat is transported poleward by oceans. In a third sensitivity test with zero O3 concentrations, global mean air temperatures are increased by 2 K because of an increase in upper tropospheric and lower stratospheric clouds. The clouds enhance the greenhouse effect within the troposphere, increasing downward longwave radiation to the surface, melting sea ice and snow. Similar studies using radiative‐convective models which do not include interactive clouds do not show such surface warming.

Original languageEnglish (US)
Pages (from-to)1513-1516
Number of pages4
JournalGeophysical Research Letters
Volume22
Issue number12
DOIs
StatePublished - Jan 1 1995

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early Earth
ozone
climate
paradoxes
troposphere
heat
oceans
greenhouse effect
sea ice
sensitivity
snow
longwave radiation
global ocean
stratosphere
surface temperature
general circulation model
sun
air temperature
warming
melting

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Earth and Planetary Sciences(all)

Cite this

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abstract = "Two features of early Earth—reduced ozone (O3) concentration and land fraction are investigated with a general circulation model (GCM). These features are components of a paradox (Faint‐Young Sun paradox) which has intrigued researchers for more than two decades. In this study, land fraction and O3 concentrations are uniformly reduced by 100 percent. The reduction in O3 takes place in the troposphere and stratosphere with all other variables held constant including present‐day land fraction. Two sensitivity tests under global ocean conditions are reported: one case with implied oceanic poleward transports of heat, the other case with no implied oceanic poleward transports of heat. The results show that the removal of land under present‐day conditions increases cloud fractions and cool surface temperatures, unless heat is transported poleward by oceans. In a third sensitivity test with zero O3 concentrations, global mean air temperatures are increased by 2 K because of an increase in upper tropospheric and lower stratospheric clouds. The clouds enhance the greenhouse effect within the troposphere, increasing downward longwave radiation to the surface, melting sea ice and snow. Similar studies using radiative‐convective models which do not include interactive clouds do not show such surface warming.",
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Early Earth's climate : Cloud feedback from reduced land fraction and ozone concentrations. / Jenkins, Gregory S.

In: Geophysical Research Letters, Vol. 22, No. 12, 01.01.1995, p. 1513-1516.

Research output: Contribution to journalArticle

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