The Headline
A new analysis of data collected by NASA's Terra satellite suggests that current models of global climate change are flawed. The study, released in the July 25 issue of the journal Remote Sensing, claims that temperature variations in Earth's climate may be attributable to cyclical oceanic phenomen such as el nino and la nina, and provides evidence that the atmosphere is more efficient at radiating excess heat than current warming models predict. If the study withstands further peer review and testing, it may fundamentally shift the predictions made by climate scientists with regard to the hypothesized anthropogenic warming of the planet.
The Science
The article's author's, Roy W. Spencer and William D. Braswell, analyzed 10 years worth of data collected by CERES (Clouds and Earth's Radiant Energy System), a sensor system in earth orbit on the Terra satellite, to address the simple but vital question of how much energy is absorbed by the atmosphere.
The major source of energy entering the atmosphere is sunlight (also called solar radiation). In fact the Earth receives about 2x1017 joules of sunlight every second, equivalent in energy to a 48 megaton explosion (two thousand times the power of the bomb dropped on Hiroshima). All of this energy has to go somewhere, and in simple terms it does one of three things. It could simply be reflected back into space, a process carried out quite efficiently by clouds and polar ice. Some incoming solar radiation will be absorbed and then re-emitted at a lower wavelength, typically infrared (IR), which can likewise travel back into space. The third and final possibility is that energy from incoming sunlight is retained by the atmosphere as heat, increasing global temperatures.
The main argument made by proponents of anthropogenic climate change (or the global warming hypothesis) is that the release of greenhouse gases by humanity will block the Earth's ability to radiate heat back into space, forcing it to be retained in the atmosphere. This then kicks off what is called a positive feedback loop whereby higher temperatures increase the amount of water vapor and methane in the air (both greenhouse gases), which traps more heat and raise the temperature and so on.
The typical approach to building climate models has been to take temperature measurements around the globe, then use this data to make determinations of how much solar radiation is being retained by the atmosphere as heat. Drs. Spencer and Braswell chose to use the inverse approach by measuring the amount of energy the earth received as sunlight and the amount reflected or radiated back into space with the delicate sensors of the Terra satellite. Armed with these two numbers they could make an accurate determination of how much heat is being retained in the atmosphere, as well as searching for correlations between decreased radiation of IR wavelengths and spikes in atmospheric temperature.The study examined data gathered between 2000 and 2010.
The results of this analysis will likely be contentious among climate scientists. According to the paper's analysis, the atmosphere is far better at radiating heat than most models predicted, and it begins doing so earlier in a warming event than scientists anticipated. In a graph from the paper (shown to the right) the authors plot predictions from IPCC (Intergovernmental Panel on Climate Change) models which represent the general consensus on how the atmosphere radiates energy in comparison to the observations of the Terra climate satellite.
Experimental observations are shown in green, while blue and red represent the IPCC conventional theories. A large mismatch between the two is clearly visible. In area 1, the graph shows a large increase in the amount of energy absorbed by the atmosphere (as measured by the total energy received from the sun minus energy reflected or re-emitted back into space) before a warming event, which is intuitive and agrees with existing models. In area 2, however, we see a rapid increase in the observed heat radiated from the atmosphere into space, even before the temperature maximum is achieved, while traditional models predict heat to be retained in the atmosphere for much longer.
The paper speculates briefly on what mechanisms might be responsible for this discrepancy, but admits that more work needs to be done. Still, if their analysis of the CERES data holds up, the atmosphere is somehow much better at radiating heat into space than is currently assumed, especially given elevated levels of carbon dioxide in the atmosphere due to human activity. Specifically the data suggests a negative feedback mechanism whereby increased temperatures are counteracted by developments which deflect and disperse the extra heat into space, preventing the kind of runaway warming which the most alarming models predict. Should this theory turn out to be correct, then the worst predictions of climate change will almost certainly turn out to be untrue. But there remains a great deal of work to be done before any such claims can be credibly made.
The Bottom Line
Even if all this paper's findings withstand the intense scrutiny that is certainly about to fall upon it, all the study does is reveal unexplained trends in the data which disagree with wide held assumptions about the way the atmosphere interacts with solar energy. It does not provide an explanation for this data beyond suggesting a few possibilities, as the authors themselves state. It certainly does not disprove or invalidate concerns about humanity's impact on the climate.
Instead it provides information that climate scientists will have to explain and incorporate into their models. Whether these enhanced models will turn out be more or less sanguine about the future of our planet remains to be determined.
http://www.uah.edu/news/newspages/campusnews.php?id=564– press release
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