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Some controversial results on the radiative forcing of our climate system as extracted from model results of the AMIP-2 and IPCC-FAR and from the radiation climatologies of the ISCCP-FD and GEWEX-SRB Seminar at CIRA-CSU Fort Collins 8 June 2006 Ehrhard Raschke (with Stefan Kinne, MPI)
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Some controversial results on the radiative forcing of our climate system as extracted from model results of the AMIP-2 and IPCC-FAR and from the radiation climatologies of the ISCCP-FD and GEWEX-SRB Seminar at CIRA-CSU Fort Collins 8 June 2006 Ehrhard Raschke (with Stefan Kinne, MPI) University of Hamburg Center for Maritime and Atmospheric Sciences (ZMAW)
Downward solar radiation anomalies at surface, from Pinker et al., 2005, Science Shortwave anomalies at TOA, from Wielicki et al., 2005, Science CONFUSION ?? ISCCP, GEWEX-SRB and CERES (+ others) produce radiation climatologies
AMIP-2 IPCC-FAR Deviations of incoming solar radiation at TOA from monthly zonal means Raschke et al., 2005, GRL
MPI-ECHAM 5 ISCCP-FD Deviations of incoming solar radiation at TOA from monthly zonal means during an entire year Raschke et al., 2005, GRL
IPCC -FAR AMIP-2 Annual global averages of TSI at TOA (Raschke, Kinne, Giorgetta, Wild, 2005, GRL)
1985 - 1988 (Raschke, Kinne, Giorgetta, Wild, 2005, GRL)
Modelers use different routines to compute spatial and temporal variations of the incoming solar radiation at TOA with the net result of often quite different meridional radiative forcing of the climate system. Instead of the calendar leap year they should follow mother nature: TROPICAL YEAR (add ¼ day each year)
Radiation budgets at surface Cox et al., 2006, AMS-RC
Data status: December 2005, new releases after 15 May 2006 1.7% 5% 18.3% 25% 25% 18.3% 5% 1.7% July 1983 to October 1995
From ISCCP documentation SRB results are based on clouds from ISCCP, and temperature and humidity profiles from the Goddard Earth Observing System-1 (GEOS-1) reanalysis product, and column ozone from the Total Ozone Mapping Spectrometer (TOMS) archive. Other ancillary data ?? (CERES products are a combination of satellite measurements with computed fluxes.) Cox et al., 2005, IRS in Butan
Radiation product Primarily sensitive to … (in some order of priority) KEEP in mind: trends can be caused by ancillary data! Insolation at TOA TSI, Astro-mechanics, spectrum, cut-off angle, care in computations Planetary albedo Clouds, surface albedo, aerosols, scene identification, angular models Outgoing longwave radiation at TOA Temperature of atmosphere and surface, water vapor, clouds, scene, angular models Downward longwave at surface Atmospheric temperature and water vapor, clouds Upward longwave at surface Surface skin temperature and effective emittance Downward solar radiation at surface Clouds, aerosols, moisture; insolation at TOA Upward solar radiation at surface Downward solar, surface albedo (and spectrum) Longwave budgets at TOA and surface; integral divergence Temperatures at surface and in the atmosphere; clouds Solar budgets at TOA and surface; integral divergence Clouds, aerosols, surface albedo
29 May 2006: GEWEX neglects l > 4mm: TSI = 1358.5 Wm-2 instead of 1367 Wm-2
Do we see an effect of the „sudden“ increase of skin temperatures in other radiation products ?
NEW DATA – May 06 ISCCP: Dw lw at sfc and CE ISCCP: OLR and CE
Solar down Terrestrial down
Times of „great“ discoveries are over; now we have to look for high accuracy and stability. Raschke et al., Int.J. Clim. 2005
ISCCP: Vertical radiative flux divergence (1991-1995) and cloud effect Raschke et al., Int.J. Clim. 2005
Summary and Recommendations: a.) Modelers must agree on same routines for insolation at TOA b.) ISCCP and SRB disagree in various radiation products in particular over high-latitude regions. c.) Both data sets might be disturbed by uncertainties in their many ancillary data, causing spurious “trends” in computed radiation fields. Independent validations required. d.) Careful validation of radiation products vs. radiation budget measurements in space and vs. ground-based network data (e.g. BSRN) is still not yet done. e.) Competition between different groups analyzing such data should be forced.