This week, the Public Broadcasting Service aired a NOVA program titled “Dimming the Earth”, which presented research by leading scientists on the complex and chaotic systems of our global climate and human activity's effect on it. One of the largest interactions (or "inputs") humans have with the atmosphere is the ever-increasing use of fossil fuels. Consumption has risen 2\% per year for this decade. More recently, atmospheric scientists have come upon the phenomenon of the reduction of  sunlight reaching Earth's surface— observing a nearly a 10\% decline since 1960. This has been dubbed the "global dimming" effect, and is now understood to be due to the way these aerosols act upon clouds.  Many scientists now believe that global dimming caused by these pollutants has mitigated the temperature rises brought about by global warming. Over the last thirty years, Earth's temperature has increased by about one, to one and a half degrees Fahrenheit . In the absence of global dimming, however, the Earth might be two to three degrees warmer than it currently is, suggesting that a "tug-of-war" exists between greenhouse gases and particulates released by burning fossil fuels. Efforts to mitigate the human health dangers of smog have allowed more heat into our atmosphere and brought about a sharper increase in global warming.
This week, the Public Broadcasting Service aired a NOVA program titled “Dimming the Earth”, which presented research by leading scientists on the complex systems of our global climate and human activity's effect on it. One of the largest interactions (or "inputs") humans have with the atmosphere is the ever-increasing use of fossil fuels. Consumption has risen 2\% per year for this decade. More recently, atmospheric scientists have come upon the phenomenon of the reduction of direct sunlight reaching Earth's surface— observing a nearly a 5\% decline between 1960 and 1990, with evidence of a recovery since then. This has been dubbed the "global dimming" effect, and is probably due to the way these aerosols act upon clouds. It is important to realise that this does not represent a net loss of this much sunshine to the climate system - if so, large temperature declines would have been observed. Instead, the sunshine is absorbed elsewhere in the system, with a much smaller net loss. Many scientists now believe that global dimming caused by these pollutants has mitigated the temperature rises brought about by global warming. Over the last thirty years, Earth's temperature has increased by about 0.5 oC . In the absence of global dimming, however, the Earth might be 0.3 oC warmer than it currently is, suggesting that a "tug-of-war" exists between greenhouse gases and particulates released by burning fossil fuels. Efforts to mitigate the human health dangers of smog have allowed more heat into our atmosphere and brought about a sharper increase in global warming.
D
and chaotic
A
direct
R
10\% decline since 1960.
5\% decline between 1960 and 1990, with evidence of a recovery since then.
R
now understood to be
probably
A
It is important to realise that this does not represent a net loss of this much sunshine to the climate system - if so, large temperature declines would have been observed. Instead, the sunshine is absorbed elsewhere in the system, with a much smaller net loss.
R
one, to one and a half degrees Fahrenheit
0.5 oC
R
two to three degrees
0.3 oC