UPDATE: December 16 2009 Sean Artman has asked an excellent question as to how a “local” effect such as the soot can raise questions on the overall effect of CO2 on the global climate. My response is below:
Dear Mr. Artman
The study that they presented has several implications:
1. The attribution of most of the warming in this region (i.e. it is certainly regional not “local” as is written since it covers tens thousands of square kilometers) which has been credited to added CO2 and other well-mixed greenhouse gases is not correct. A significant fraction of the warming is from the soot.
2. The heating of the atmosphere from the soot (by solar absorption and decrease in long wave loss to space) results in alterations of pressure fields, and thus wind circulations. This effect will communicate through the pressure field to long distances from this region (e.g. see our paper
Matsui, T., and R.A. Pielke Sr., 2006: Measurement-based estimation of the spatial gradient of aerosol radiative forcing. Geophys. Res. Letts., 33, L11813, doi:10.1029/2006GL025974
on this subject.
3. The effect of soot is not limited to this region. It has been implicated in Arctic warming also; e.g. see
where it is written
“…..on snow.even at concentrations below five parts per billion.such
dark carbon triggers melting, and may be responsible for as much as 94
percent of Arctic warming.”
There is a news release that indicates the major effect of soot on the climate, including glaciers, in the Himalayas (thanks to Charles Martin for alerting us to this!). The news release dated December 14 2009 is
Excerpts from the news article are
“……the new research, by NASA’s William Lau and collaborators, reinforces with detailed numerical analysis what earlier studies suggest: that soot and dust contribute as much (or more) to atmospheric warming in the Himalayas as greenhouse gases. This warming fuels the melting of glaciers and could threaten fresh water resources in a region that is home to more than a billion people.”
“The Indo-Gangetic plain, one of the most fertile and densely populated areas on Earth, has become a hotspot for emissions of black carbon……. Winds push thick clouds of black carbon and dust, which absorb heat from sunlight, toward the base of the Himalayas where they accumulate, rise, and drive a “heat pump” that affects the region’s climate.”
“Over areas of the Himalayas, the rate of warming is more than five times faster than warming globally,” said William Lau, head of atmospheric sciences at NASA’s Goddard Space Flight Center in Greenbelt, Md. “Based on the differences it’s not difficult to conclude that greenhouse gases are not the sole agents of change in this region. There’s a localized phenomenon at play.”
“He has produced new evidence suggesting that an “elevated heat pump” process is fueling the loss of ice, driven by airborne dust and soot particles absorbing the sun’s heat and warming the local atmosphere and land surface. A related modeling study by Lau and colleagues has been submitted to Environmental Research Letters for publication.”
“……said Lau. “We need to add another topic to the climate dialogue.”
This news study reinforces the conclusion that a broader perspective of the role of humans in the climate system is needed, and that the radiative effect of CO2 may not the dominate human role as concluded by the IPCC report and as being discussed in Copenhagen.