Air Pollution Linked to Droughts and Major Storms

A groundbreaking new study has found an increase in air pollution can reduce rainfall in drought-affected regions and worsen the severity of storms in wet regions or seasons.

Researchers have discovered that increases in air pollution and other particulate matter in the atmosphere can strongly affect cloud development in ways that reduce precipitation in dry regions or seasons.

This while increasing rain, snowfall and the intensity of severe storms in wet regions or seasons, according to results of a new study. The research provides the first clear evidence of how aerosols - soot, dust and other particulates in the atmosphere - may affect weather and climate. The findings have important implications for the availability, management and use of water resources in regions across the United States and around the world.

"Using a 10-year dataset of atmospheric measurements, we have uncovered the long-term, net impact of aerosols on cloud height and thickness and the resulting changes in precipitation frequency and intensity," says Zhanqing Li, an atmospheric scientist at the University of Maryland and lead author of a paper reporting the results.

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Asian Air Pollution Behind Rising Global Temperatures

Coal-derived emissions pouring from smokestacks across Asia are--perhaps counterintuitively--responsible for a pause in global warming in the decade following 1998, but that’s no real reason to celebrate. The halt in rising temperatures is a result of the large amounts of sulfur in those emissions, which can have a cooling effect on the planet. But the huge spike in greenhouse gas emissions is still very real, and over time its delayed impacts will be realized when emerging countries rein in pollution.

           At least, that’s the latest on the global warming front via a paper released Monday by researchers at several universities, including Boston and Harvard Universities in the States and Finland’s University of Turku. The halt in rising global temps from 1998 to 2008 is something of a mirage, the researchers say, and the effects of all that carbon that went into the air alongside the sulfur will become apparent in the long term.

          The paper, if taken as truth, ties up a loose end for those who believe global warming is a man-made phenomenon. From 1998 to 2008, global temperatures were flat even as the developing world spewed tons upon tons of carbon emissions into the atmosphere, increasing global carbon dioxide emissions from burning fossil fuels by at third. Some called this evidence that global temperatures and carbon emissions aren’t as directly linked as some might like to think.

           But most of those carbon emissions came from coal fueling the explosive growth of Asian economies, and with coal emissions comes sulfur. Sulfur is a key ingredient in the formation of aerosols, which form hazy cloud layers that reflect heat from the sun back into space. These aerosols, the paper argues, are responsible for the halt in rising temperatures.

          But the halt in rising temperatures isn’t likely to last, the researchers say. When emerging economies begin to take a harder line against pollution, those sulfur emissions will decline as well. And while sulfur can persist in the atmosphere for several years, eventually those aerosols will disperse and global temperatures will begin climbing again, this time with countless more tons of carbon already in the atmosphere.

          

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Posted in: aerosols,air. global warming,atmosphere,carbon emissions,china,coal,environment,pollution

Good Particles In Upper Atmosphere

         

     A study published July 21 in Science and led by Susan Solomon, of the National Oceanographic and Atmospheric Administration (NOAA), presents new evidence that particles located in the upper layer of the atmosphere -- also called the stratosphere -- have played a significant role in cooling the climate in the past decade, despite being at persistently low levels.

                    According to the paper, "The Persistently Variable 'Background' Stratospheric Aerosol Layer and Global Climate Change," stratospheric aerosols, which are small droplets consisting of sulfuric acid and water, have been reflecting some sunlight back into space, which would have otherwise warmed the Earth.


                    "Stratospheric aerosols are a small variable in the climate change equation," said Larry Thomason, a scientist at NASA's Langley Research Center in Hampton, Va and co-author on the paper. "But if you compare the climate system to a balanced scale, it doesn't take much to tip that scale. Stratospheric aerosols have that potential."


  Volcanic plumes modulate the amount of stratospheric aerosols significantly. Even in times when there aren't large eruptions, such as the past decade, these aerosols have remained present, leaving a consistent background level.

                    Thomason and Jean-Paul Vernier, a co-author on the paper and a NASA Post-Doctoral Fellow at Langley, have worked closely with colleagues to build a record of stratospheric aerosol observations with satellite instruments, which have observed the presence of sulfuric acid droplets in the stratosphere. NASA's Stratospheric Aerosol and Gas Experiment (SAGE II) monitored them from 1984 to 2005, and the joint NASA/CNES Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) has been able to estimate the amount of particles in the stratosphere since its launch in 2006. The NASA data was also combined with data from Global Ozone Monitoring by Occultation of Stars (GOMOS), a European Space Agency instrument. These results, which have been reported in the June 30, 2011 issue of Geophysical Research Letters, show that there has been a slow increase of the stratospheric aerosols during the past decade.
            
                      "None of the climate models, including those used by the IPCC [Intergovernmental Panel on Climate Change] incorporate this slow increase," said Vernier. "If you do not include this effect, you are going to miss a significant cooling component during this decade."
                       These stratospheric aerosols that need to be taken into account are heavily influenced by a natural source - volcanic eruptions.

                       When a volcanic plume reaches the stratosphere, it may inject sulfur dioxide. Within a month, the sulfur dioxide transforms into sulfuric acid droplets, which linger in the stratosphere and reflect sunlight. Human activities, such as burning wood and coal, can also increase the amount of sulfate aerosols in the stratosphere; however, human-caused effects are small compared to those of volcanoes.

      "Even in times without major eruptions, the role of the stratosphere's sulfuric aerosol in climate has remained significant. If they are neglected, it can result in overestimates of global warming in coming decades, particularly if these aerosols remain present at current values or increase," said Thomason.

Millions of tons of sulfur dioxide gas from a major volcanic eruption can reach the stratosphere. After converting to sulfuric acid droplets, these aerosols reflect energy coming from the sun, thereby preventing the sun's rays from heating Earth's surface.

                 Vernier explains that the radiative effects of aerosols are noteworthy - about 1/3 that of carbon dioxide over the past decade. The average radiative forcing between 2000 and 2010 by stratospheric aerosols has cooled the Earth down at 0.1 watts per meter squared, while the amount of carbon dioxide emitted in the same decade has warmed the Earth at 0.3 watts per meter squared.
www.nasa.gov


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