Alternate Title: On Pinker et al 2005 and the Positive Trend in the NCEP-DOE Reanalysis-2 Surface Downward Solar Radiation Flux
Over at Tallbloke’sTalkshop, Tallbloke has a post about the Pinker et al 2005 paper “Do Satellites Detect Trends in Surface Solar Radiation?” I’ve included (cross posted) that post in this one. Second, a positive trend also appears in the NCEP-DOE Reanalysis-2 Surface Downward Solar Radiation Flux data that’s available through the NOAA NOMADS website, though the positive trend is not as significant. Not too surprising, the multi-model ensemble mean of the climate models prepared for the IPCC’s upcoming 5th Assessment Report (AR5) do not show an increase in downward solar radiation at the surface. Another model failure to add to the ever-growing list?
First, Tallbloke’s post: Keep in mind, the satellite-based surface solar radiation flux “data” presented in Pinker et al is not based on direct measurements. It is calculated primarily from ISCCP cloud amount data. [I’ve added figure numbers to the following illustrations for my post.]:
Errrmm, why I have not heard of this 2006 [sic] paper before? 1.6W/m^2 per decade is a not insignificant trend. Did the IPCC ignore this?
Do Satellites Detect Trends in Surface Solar Radiation?
R. T. Pinker,1 B. Zhang,2 E. G. Dutton3
Long-term variations in solar radiation at Earth’s surface (S) can affect our climate, the hydrological cycle, plant photosynthesis, and solar power. Sustained decreases in S have been widely reported from about the year 1960 to 1990. Here we present an estimate of global temporal variations in S by using the longest available satellite record. We observed an overall increase in S from 1983 to 2001 at a rate of 0.16 watts per square meter (0.10%) per year; this change is a combination of a decrease until about 1990, followed by a sustained increase. The global-scale findings are consistent with recent independent satellite observations but differ in sign and magnitude from previously reported ground observations. Unlike ground stations, satellites can uniformly sample the entire globe.
Figure 1 (Figure 1 from Pinker et al)
[END OF CROSSPOST]
As blogger Roger Andrews noted in his April 11, 2013 at 3:29 am comment at Tallbloke’sTalkshop:
According to Pinker et al’s Figure 5, reproduced below for reference, solar radiation over the oceans increased by about 5 w/m2 between 1983 and 2001 while solar radiation over land areas decreased slightly. How does this happen?
Figure 2 (Figure 5 from Pinker et al)
Also, does anyone have an explanation for the abrupt +/- 10 w/m2 downward excursion in the ocean record in 1994?
INTRODUCTION TO THE NCEP-DOE REANALYSIS-2 SURFACE DOWNWARD SOLAR RADIATION
The NCEP-DOE Reanalysis-2 is discussed in the 2002 Kanamitsu et al paper NCEP-DOE AMIP-II Reanalysis (R-2). The reanalysis begins in 1979 and at present runs through March 2013. Surface Downward Solar Radiation (radiation from the sun at the surface of the Earth) is one of the NCEP-DOE Reanalysis-2 fields available through the NOAA NOMADS website here, where it’s identified as “DSWRFsfc * surface Downward solar radiation flux [W/m^2]” in the drop-down “Fields” menu. Kanamitsu et al identifies Chou (1992) “A solar radiation model for use in climate studies” and Chou and Lee (1996) “Parameterizations for the absorption of solar radiation by water vapor and ozone” as the bases for the surface downward solar radiation flux outputs.
The NOAA NOMADS website allows users to select global coordinates for the desired outputs, so we’ll look at a few subsets in addition to the global values. The outputs are presented by the NOAA NOMADS website as absolute values, so I’ve converted them to anomalies using the base years of 1981-2010.
Keep in mind, this reanalysis is the output of a computer model—one that includes measurements (data) as inputs. It’s is not “raw” observations-based data.
Figure 3 shows the global surface downward solar radiation flux anomalies from January 1979 to present, based on the NCEP-DOE Reanalysis-2. I’ve also included a linear trend line, which shows that the global values increased at a rate of about 0.22 Watts/m^2/decade since 1979, which is significantly less than the trend for the shorter period presented by Pinker et al (2005). The output includes lots of variability, what some would consider noise, so I’ve smoothed the output values with a 13-month running average filter in Figure 4.
Surface downward solar radiation is one of the variables from the CMIP5-archived climate models that are available through the KNMI Climate Explorer. Refer to the Radiation Variables, where it is identified as “rsds”. As you’ll recall, the CMIP5 archive is being used for the IPCC’s upcoming 5th Assessment Report (AR5). According to the multi-model ensemble mean of the CMIP5-stored models, using the RCP6.0 scenarios, the downward solar radiation at the surface should have been flat (decreasing slightly) during this period, if manmade greenhouse gases were responsible for global warming. But based on the Pinker et al (2005) paper and the NCEP-DOE Reanalysis-2, surface downward shortwave radiation increased significantly. The linear trends of the CMIP5 multi-model mean and the NCEP-DOE reanalysis are compared in Figure 5. Both model outputs have been smoothed in Figure 6.
REANALYSIS COMPARISON – TROPICS VS EXTRATROPICS
In this preliminary look at the surface downward solar radiation outputs from the NCEP-DOE Reanalysis-2, I’ve also broken down the globe into 3 subsets: the Tropics (24S-24N) and the Extratropics for the Northern and Southern Hemispheres (24N to 90N and 90S to 24S, respectively). The Northern Extratropics show little trend in surface downward solar radiation, Figure 7, while Tropics at 0.28 Watts/m^2/Decade and Southern Extratropics at 0.32 Watts/m^2/Decade both show significant increases in downward solar radiation at the surface. I’ve smoothed the outputs for the three regions in Figure 8.
The tropical and extratropical regions are presented individually in Figures 9 through 11 for anyone interested.
On the thread at Tallbloke’sTalkshop, blogger Ned Nikolov in his April 10, 2013 at 11:37 pm comment also recommended Wild (2009) Global dimming and brightening: A review, and Pallé et al (2009) “Interannual variations in Earth’s reflectance 1999–2007”.
If there has been a rise in surface downward solar radiation since the late-1970s, early-1980s somewhere between the magnitudes presented by the NCEP-DOE Reanalysis-2 and Pinker et al (2005), then the hypothetical impacts of manmade greenhouse gases have obviously been overstated—especially when one considers that the IPCC’s climate models used for the attribution of global warming failed to simulate this rise in downward solar radiation at the surface over that period.
Another climate model failure comes as no surprise. In our earlier model-data comparisons, the CMIP5-archived models failed to properly simulate:
To paraphrase Edwin Starr’s song “War”:
Climate Models. What’re they good for? Absolutely nothing.