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Radiative forcing ‐ measured at Earth's surface ‐ corroborate the increasing greenhouse effect
Author(s) -
Philipona Rolf,
Dürr Bruno,
Marty Christoph,
Ohmura Atsumu,
Wild Martin
Publication year - 2004
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2003gl018765
Subject(s) - longwave , radiative forcing , cloud forcing , atmospheric sciences , environmental science , forcing (mathematics) , greenhouse gas , radiative transfer , humidity , greenhouse effect , climatology , radiative flux , atmosphere (unit) , climate model , climate change , global warming , meteorology , physics , aerosol , geology , oceanography , quantum mechanics
The Intergovernmental Panel of Climate Change (IPCC) confirmed concentrations of atmospheric greenhouse gases and radiative forcing to increase as a result of human activities. Nevertheless, changes in radiative forcing related to increasing greenhouse gas concentrations could not be experimentally detected at Earth's surface so far. Here we show that atmospheric longwave downward radiation significantly increased (+5.2(2.2) Wm −2 ) partly due to increased cloud amount (+1.0(2.8) Wm −2 ) over eight years of measurements at eight radiation stations distributed over the central Alps. Model calculations show the cloud‐free longwave flux increase (+4.2(1.9) Wm −2 ) to be in due proportion with temperature (+0.82(0.41) °C) and absolute humidity (+0.21(0.10) g m −3 ) increases, but three times larger than expected from anthropogenic greenhouse gases. However, after subtracting for two thirds of temperature and humidity rises, the increase of cloud‐free longwave downward radiation (+1.8(0.8) Wm −2 ) remains statistically significant and demonstrates radiative forcing due to an enhanced greenhouse effect.