AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Intersection of Aerosols with Climate Change: Why Policy Makers Should Include Aerosols at the UN Paris-2015 Summit
RAMANATHAN VEERABHADRAN, Scripps Institute of Oceanography
Abstract Number: 617 Working Group: Invited by Conference Chair
Abstract The role of anthropogenic activities in emissions of greenhouse gases is well known. The buildup of over one billion tons of greenhouse gases already in the atmosphere in conjunction with business as usual emissions during the next few decades have set the planet on a course for a 2.5C warming by mid-21st century and as much as 4C by end of the 21st century. By sheer coincidence, human activities have also simultaneously polluted the air with emissions of aerosols, which have offset about 40% of the committed warming by reflecting the incoming solar radiation. The best analogue is, if we can think of the greenhouse gases as a blanket covering the planet (keeping it warm by trapping the infrared energy), aerosols have acted like mirrors and reflected sunlight and cooled the planet. This is at best a Faustian bargain since these particles have also led to global dimming at the surface thus altering in a fundamental way the hydrological cycle of the planet. One simulated impact of the dimming is to cause droughts and disruption of the major precipitation systems in the tropics, particularly affecting the poorest three billion. Another double jeopardy is that, not all particles have a cooling effect. Some like black and brown carbon are efficient absorbers of solar radiation and when they are deposited on snow and ice lead to accelerated melting of arctic sea ice and glaciers in the Alps and the Himalayas. The fundamental policy mistake that is being made is to assume that aerosols are minor players in climate change or even if they are taken seriously to adopt the view that they are lessening the impacts of global warming through their cooling effect. One evidence of this flawed thinking is the geo-engineering proposal of releasing sulfate particles in the stratosphere. They do indeed can cause cooling but they are equally likely to reduce global precipitation affecting the water security which in many parts of the planet is a more serious problem than temperature change. The effect of aerosols on the water security of the planet deserves serious consideration at the UN Paris summit of 2015 and we need to drastically reduce their emissions. Unlike the case of reducing CO2 emissions, cost-effective and proven technologies are readily available to cut most manmade aerosols.