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Scientists from SEI help launch major climate study

Posted on 14 June 2011

Fast action on pollutants such as black carbon, ground level ozone and methane may help limit near term global temperature rise and significantly increase the chances of keeping temperature rise below 2 degrees C, says a new assessment launched today.

The Stockholm Environment Institute at the University of York has played a key role in a new United Nations Environment Programme (UNEP)/World Meteorological Organization (WMO) Assessment of how to reduce the impact of black carbon and tropospheric ozone which adversely affect public health, crop yields and contribute to climate change.

The biggest impacts of reducing their emissions and concentrations are seen in the regions where action is taken. This is especially true for the public health impacts, but also follows for crop yields and regional climate impacts.

Dr Johan Kuylenstierna

The study concludes that protecting the near-term climate is central to significantly cutting the risk of “amplified global climate change” linked with rapid and extensive loss of Arctic ice on both the land and at sea.

Fast action might also reduce losses of mountain glaciers linked in part with black carbon deposits while reducing projected warming in the Arctic over the coming decades by two thirds.

Scientists also point to numerous public health and food security opportunities beyond those linked with tackling climate change.

Big cuts in emissions of black carbon will improve respiratory health; reduce hospital admissions and days lost at work due to sickness, says the assessment whose Secretariat is provided by the Stockholm Environment Institute. Close to 2.5 million premature deaths from outdoor air pollution could on average be avoided annually world-wide by 2030 with many of those lives saved being in Asia, the assessment suggests.

Big cuts in ground level ozone could also contribute to reduced crop damage equal to between one and four per cent of the annual global maize, rice, soybean and wheat production.

Cutting these so-called ‘short-lived climate forcers’ can have immediate climate, health and agricultural benefits, the report concludes. This is because, unlike carbon dioxide (CO2) which can remain in the atmosphere for centuries black carbon, for example, only persists for days or weeks.

The researchers, however, also underline the fact that while fast action on black carbon and ground level ozone could play a key role in limiting near-term climate, immediate and sustained action to cut back CO2 is crucial if temperature rises are to be limited over the long-term.

It is the combination of action on short-lived climate forcers and long-lived greenhouse gases which improves the chances of keeping below the 2 degree target throughout the 21st Century.

The findings, released today in Bonn, Germany during a meeting of the UN Framework Convention on Climate Change (UNFCCC) have been compiled by an international team of more than 50 researchers chaired by Drew Shindell of the National Aeronautics and Space Administration (NASA).

This included researchers at the Stockholm Environment Institute at the University of York, led by Dr Johan Kuylenstierna, who was scientific coordinator and a lead author. SEI researchers Dr Kevin Hicks and Dr Harry Vallack were also lead authors and Dr Lisa Emberson was coordinating lead author of the chapter on impacts.  

Dr Kuylenstierna said: “In addition to the global benefits of reducing short-lived climate forcers, the regional nature of the benefits of reducing black carbon and tropospheric ozone should appeal to policy makers. The biggest impacts of reducing their emissions and concentrations are seen in the regions where action is taken. This is especially true for the public health impacts, but also follows for crop yields and regional climate impacts.

“Also, the problem of short-lived climate forcers is not one that must wait for a technological solution. Rather, the solutions exist and the challenge that remains is one of strategic planning, financing and policy focus.”

Achim Steiner, UN Under-Secretary General and UNEP Executive Director, said: “There are now clear, powerful, abundant and compelling reasons to reduce levels of pollutants such as black carbon and tropospheric ozone along with methane: their growing contribution to climate change being just one of them.

“This assessment underlines how the science of short lived climate forcers has evolved to a level of maturity that now requires and requests a robust policy response by nations. The experts spotlight how a small number of emission reduction measures targeting, for example, recovery of methane in the coal, oil and gas sectors through to the provision of cleaner burning cook stoves; particle traps for diesel vehicles and the banning of open burning of agricultural wastes - offer dramatic public health, agricultural, economic and environmental benefits.”

The UNEP/WMO Integrated Assessment of Black Carbon and Tropospheric Ozone suggests that action could be catalyzed through not only the UN climate convention process but also via, for example, strengthening existing national and regional air quality agreements.

Notes to editors:

  • Black carbon is a major component of soot and is formed from the incomplete combustion of fossil fuels, wood and biomass. Key sources include emissions from cars and trucks; cookstoves; forest fires and some industrial facilities. It affects the climate by intercepting and absorbing sunlight and darkens snow and ice when deposited, while also influencing cloud formation. It is also a health hazard.

    Nine actions are pin pointed in the assessment for black carbon, all of which could be undertaken today including:-
    • Diesel particle filters for vehicles as part of combined standards on vehicle emissions and fuels
    • Replacing wood burning stoves in developed countries with pellet stoves and boilers using fuel from recycled wood and sawdust
    • Clean-burning biomass stoves for cooking and heating in developing countries
    • Banning open burning of agricultural wastes
    • Replacing traditional brick kilns with vertical shaft and Hoffman kilns
  • Tropospheric ozone is a major component of urban smog, is a powerful greenhouse gas and air pollutant harmful to human health and ecosystems. The threefold increase in concentrations in the northern hemisphere in the past 100 years has made it the third most important global greenhouse gas. Tropospheric ozone is formed from other gases including methane - itself a potent greenhouse gas emitted from sources such as waste tips, livestock and the oil and gas industry.

    Seven actions are pinpointed for addressing ground level ozone which hinge on addressing methane emissions including:-
    • Encouraging composting and other measures to curb organic wastes going to landfill
    • Upgrading water treatment works to include gas recovery
    • Measures to cut methane emissions from the coal, oil and gas industries, including cutting leaks from long distance gas pipelines and promoting anaerobic digestion of manure from cattle and pigs
    • Intermittent aeration of continuously flooded paddy fields
  • The summary for decision makers and full UNEP/WMO Integrated Assessment of Black Carbon and Tropospheric Ozone report can be found at
  • The UN Climate Change Conference June 2011
  • UNEP’s work on climate change
  • WMO, the U.N. system’s authoritative voice on weather, water and climate, is at
  • Stockholm Environment Institute is an independent international research institute. The Institute has established a reputation for rigorous and objective scientific analysis in the field of environment and development. SEI’s goal is to bring about change for sustainable development by bridging science and policy. Further information at
  • Further Information on the Stockholm Environment Institute at York at

Contact details

Caron Lett
Press Officer

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