There is an important new paper to appear in JGR [and thanks to Mike Jonas for altering us to it!]. It is
Pallé, E., P. R. Goode, and P. Montanes-Rodriguez (2009), Inter-annual trends in Earth’s reflectance 1999-2007, J. Geophys. Res., doi:10.1029/2008JD010734, in press. (accepted 21 November 2008)
The abstract reads
“The overall reflectance of sunlight from Earth is a fundamental parameter for climate studies. Recently, measurements of earthshine were used to find large decadal variability in Earth’s reflectance of sunlight. However, the results did not seem consistent with contemporaneous independent albedo measurements from the low Earth orbit satellite, CERES, which showed a weak, opposing trend. Now, more data for both are available, all sets have been either re-analyzed (earthshine) or re-calibrated (CERES), and present consistent results. Albedo data are also available from the recently released ISCCP FD product. Earthshine and FD analyses show contemporaneous and climatologically significant increases in the Earth’s reflectance from the outset of our earthshine measurements beginning in late 1998 roughly until mid- 2000. After that and to date, all three show a roughly constant terrestrial albedo, except for the FD data in the most recent years. Using satellite cloud data and Earth reflectance models, we also show that the decadal scale changes in Earth’s reflectance measured by earthshine are reliable, and caused by changes in the properties of clouds rather than any spurious signal, such as changes in the Sun-Earth-Moon geometry.”
The conclusion includes the text
“In this paper, we have demonstrated that the agreement between earthshine and CERES reflectances have shown a dramatic improvement after CERES data were re-calibrated and earthshine data were re-analyzed. In the common period, earthshine, CERES along with ISCCP-FD data show a trendless albedo. However, preceding CERES, earthshine and ISCCP-FD reflectances show a significant increase before flattening and holding the increase. This implies a reduction in the net sunlight reaching Earth. In the context of the recent climate change, it is important to point out that the physical causes behind these large decadal variations in albedo are still unknown, and that we just don’t know yet whether we should expect the albedo changes observed during the modern period to persist into the future.
Further, we have demonstrated that the trend toward an increasing terrestrial albedo seen in the earthshine is due to evolving cloud properties, rather than sampling problems or issues arising from the Sun-Earth-Moon geometry.”
Since, as communicated in the Figure provided by Josh Willis in the recent article
Pielke Sr., R.A., 2008: A broader view of the role of humans in the climate system. Physics Today, 61, Vol. 11, 54-55
upper ocean heating has discontinued since 2004, their results are consistent with that independent observational measurement.
The new 2009 Pallé et alstudy further highlights the limited understanding that we still have of the role of natural and human climate forcings.