UN Environment Programme, World Meteorological Organization
http://www.unep.org/gc/gc26/download.asp?ID=2197
[From Press Release] Using existing technologies and institutions to cut two local air pollutants can save millions of lives and avoid tens of billions of dollars of crop losses annually, while halving regional warming for 30 to 60 years. This will reduce the risk that the Arctic, Himalayas and other critical ecosystems will tip into irrevocable and potentially catastrophic changes, such as the accelerated melting of permafrost, which releases methane and carbon dioxide—the top two climate forcers.
These are among the findings of a new scientific assessment from the United Nations Environment Programme (UNEP) and World Meteorological Organization (WMO), in collaboration with a global team of scientists released this week by UNEP at its Governing Council meeting in Nairobi.
The two local air pollutants are sooty dust known as black carbon and ground-level ozone in the troposphere. (This is different from the good ozone in the upper atmosphere, or stratosphere, that shields us from harmful ultraviolet rays.)
These local air pollutants can be cut with technologies that are already in use around the world at scale, and through existing laws and institutions at the national and regional level that already have the expertise needed to control air pollution….
The benefits can come quickly, in years to a couple of decades. This is in contrast to cuts in CO2, which do little to help climate in the next few decades, but are nonetheless essential to avoid long-term warming after 2070 and beyond.
The world can cut the rate of warming in half and stay below the critical 1.5˚C guardrail for 30 or more years by cutting black carbon and ground-level ozone, according to the UNEP/WMO Assessment. During the 2009 UN climate change talks in Copenhagen, more than 100 countries called for fast action to keep from passing the 1.5˚C mark, which an increasing number of climate scientists say is the outer limit for climate impacts the world can adapt to.
The UNEP/WMO Assessment also calculates that cuts in black carbon and bad ozone can, along with expected CO2 cuts, delay passing the 2C level for 60 years. The 2˚C limit was set earlier by the biggest climate emitters, including the US, Europe, Japan, and China….
The measures analyzed in the UNEP/WMO Assessment would go a long way toward protecting one of the world’s most vulnerable regions – the Arctic. The Assessment builds on a 2010 paper published by Mark Jacobson that calculates that controlling black carbon may be the only way to save the Arctic – a key defensive shield that reflects heat back to space – from runaway loss of ice. A 2009 paper by Drew Shindell, who chaired the Assessment, and Greg Faluvegi, calculates that black carbon is responsible for 50 percent of the total 1.9˚C increased Arctic warming from 1890 to 2007. Black carbon is a key warming agent for other glaciated regions as well, including the Himalayan-Tibetan Plateau in Asia, which is the main source of fresh water for hundreds of millions of people.
