HR: 0830h
AN: PP21B-1169    [PDF]
TI: Radiative Forcing - Measured at Earth's Surface - Corroborate the Increasing Greenhouse Effect
AU: * Philipona, R
EM: rphilipona@pmodwrc.ch
AF: Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center, Dorfstrasse 33, Davos Dorf, 7260 Switzerland
AU: Duerr, B
EM: bduerr@pmodwrc.ch
AF: Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center, Dorfstrasse 33, Davos Dorf, 7260 Switzerland
AU: Marty, C
EM: chmarty@gmx.net
AF: Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center, Dorfstrasse 33, Davos Dorf, 7260 Switzerland
AU: Ohmura, A
EM: ohmura@geo.umnw.ethz.ch
AF: Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology, Winterthurerstr. 190, Zuerich, 8057 Switzerland
AU: Wild, M
EM: wild@geo.umnw.ethz.ch
AF: Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology, Winterthurerstr. 190, Zuerich, 8057 Switzerland
AB: 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 detected with instrumental measurements at Earth's surface so far. Here we show that atmospheric longwave downward radiation significantly increased (+5.2 Wm$^{-2}$) partly due to increased cloud amount (+1.0 Wm$^{-2}$), while solar shortwave radiation decreased (-2.0 Wm$^{-2}$) over eight years of measurements at eight radiation stations distributed over the central Alps. With cloud effects subtracted, model calculations show the cloud-free longwave flux increase (+4.2 Wm$^{-2}$) to be in due proportion to the increase of temperature (+ 0.82 $^{o}$C) and absolute humidity (+0.21 g m$^{-3}$), but to be three times larger than expected from anthropogenic greenhouse gases, and therefore in part related to rising warm air advection under strengthened NAO conditions. However, after correcting for two thirds of the temperature and humidity rises, the increase of cloud-free longwave downward radiation (+1.8 Wm$^{-2}$) remains significant and demonstrates anthropogenic greenhouse gas radiative forcing.
DE: 0325 Evolution of the atmosphere
DE: 1704 Atmospheric sciences
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting