by Steve McGee
Unlike many fiscal budgets, earth’s energy budget is widely believed to be in surplus.
With each year of increasing amounts of greenhouse gasses, earth is modeled to send less energy outward than it receives from the sun. This energy surplus, as understood, continues until the global average temperature rises sufficiently to restore balance by emitting more energy in accordance with the Stefan-Boltzmann Law. Indeed, the concept of ‘missing heat’ implies that a surplus of energy exists to be missed. And the NASA GISS Model E projects a trend of increasing energy surplus. The runs of Model E for “Dangerous Human-Made Interference” (from 2007) A1B scenario ( available at link) yield this projection for net radiance at the top of the atmosphere:
Notice the increasing trend of anomalous net radiance.
With this in mind, but on another matter I recently examined the Climate Forecast System Reanalysis. The CFSR is a newer reanalysis described by Saha, Suranjana, and Coauthors, in 2010: The NCEP Climate Forecast System Reanalysis. Bull. Amer. Meteor. Soc., 91, 1015.1057. doi: 10.1175/2010BAMS3001.1
The CFSR monthly data sets are available at [link].
The CFSR is the first reanalysis from NCEP to use radiance observations from the menagerie of past satellites. The CFSR also uses the AER RRTM radiative model to fill in the gaps of satellite data. The RRTM is the same radiative code used by many climate models. By subtracting the top of the atmosphere outgoing infrared from the net shortwave radiative flux, one arrives at the net radiative flux. And by dividing the outgoing shortwave radiative flux by the incoming shortwave radiative flux, one arrives at albedo. Examples for March of 1979 appear as:
Due to missing values, all data for the year 1994 are excluded. By calculating the spatially weighted global annual averages, the time series of various fields yield interesting results. The data for the top of the atmosphere net radiance appear as:
The CFSR Net Radiance data indicate radiative deficit following the El Chichon volcanic eruption in 1982, and again following the Mount Pinatubo volcanic eruption in 1991. Also, the peak net radiative surplus appears during 1997 which coincides with the anomalously warm El Nino event. I was quite surprised, however, to note that the years 2001 through 2008 indicate net radiative deficit and that the overall trend was toward decreasing net radiance.
Should I have been surprised? Perhaps not. Net radiation, particularly the shortwave component, is known to be quite difficult to measure because shortwave reflection varies greatly with respect to the angle of observation depending upon the composition, size, shape, and orientation of clouds and earth’s surface. Further, the very process of reanalysis can add spurious errors. That is why NCAR ( the National Center for Atmospheric Research ) warns that reanalysis should not be equated with “observations” or “reality.”
Still, while not “observation” nor “reality”, the CFSR does represent a best assessment of the recent climate based on observations and the same radiative codes that lie within the prognostic climate mod
So what does this imply?
- To the extent that the CFSR radiance is accurate, it implies that earth was in radiative deficit, not surplus, for the decade of the 2000s and that for this decade, there is no ‘missing heat’ to be found.
- The negative trend in CFSR net radiation implies a divergence from the NASA GISS model projections cited above.
- The CFSR net radiative deficit also implies that energy loss to space, rather than shifting of energy within the climate system may be responsible for the negative trend since 2001 in many of the global temperature data sets.
Biosketch: Steve McGee has a bachelor of science degree in meteorology. His long career of software engineering includes the development of numerous defense related systems providing analysis and display weather and atmospheric effects.
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