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SEI has key role in blueprint to cut pollutants' impact on climate

Posted on 25 February 2011

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 study commissioned by the United Nations, in consultation with international partners provides science-based advice on ways to cut the impacts of these pollutants. It was discussed at a UNEP Governing Council, Global Ministerial Environment Forum in Nairobi this week and will be launched on 5 June - Environment Day.

Along with methane – a major ozone precursor and a potent greenhouse gas – black carbon and tropospheric (ground level) ozone are known as short-lived climate forcers (SLCFs) as they have a limited lifetime in the atmosphere – ranging from days to a decade – in comparison with carbon dioxide (CO2).

The UNEP/WMO Assessment is designed to link knowledge to action and science to policy, providing a scientifically credible basis for informed decision-making. A team of researchers at Stockholm Environment Institute at the University of York, led by Dr Johan Kuylenstierna, co-ordinated and helped to write the assessment, which was chaired by Dr Drew Shindell of the NASA-Goddard Institute for Space Studies (GISS).

It is a comprehensive analysis of drivers of emissions, trends in concentrations, and impacts on climate, human health and ecosystems of BC, tropospheric O3 and its precursors.

The Assessment shows how a small number of emission reduction measures, targeting black carbon and ozone precursors, could begin to protect climate, public health, water and food security, and ecosystems. They include the recovery of methane from coal, oil and gas extraction and transport, methane capture in waste management, use of clean-burning stoves for residential cooking, diesel particulate filters for vehicles and a ban on field burning of agricultural waste. Widespread implementation is achievable using existing technologies though significant and strategic investment and institutional arrangements would be required.

The Assessment’s integrated analysis determines that under current policies, emissions of BC and O3 precursors are expected globally either to increase or to remain roughly constant unless further mitigation action is taken.

The Integrated Assessment of Black Carbon and Tropospheric Ozone convened more than 50 authors to assess the state of science and existing policy options for addressing these pollutants.

The Assessment team examined policy responses and developed an outlook to 2070 illustrating the benefits of political decisions made today and the risks to climate, human health and crop yields if action is delayed.

With a premium on robust science and analysis, the Assessment was driven by four main policy-relevant questions:

  • Which measures are likely to provide significant combined climate and air quality benefits?
  • How much can implementation of the identified measures reduce the rate of global mean temperature increase by midcentury?
  • What are the multiple climate, health and crop-yield benefits that would be achieved by implementing the measures?
  • By what mechanisms could the measures be rapidly implemented?

Dr Kuylenstierna said: “The assessment of current science confirms that reducing these substances can slow global warming over the short term, reduce regional climate change impacts, and provide health and agricultural benefits by reducing air pollution. We present policy options that could become part of a comprehensive Action Plan for slowing climate change over the next two decades by targeting reductions of short-lived climate forcers.

“This action has to be complementary to reducing long-lived greenhouse gases, particularly carbon dioxide, but provides an opportunity to avoid exceeding important climate change targets over the course of this century. The co-benefits of taking action on health, crop yields and ecosystem protection are considerable, and will be felt mostly by the countries in the regions who take the action.”

Notes to editors:

  • The Assessment relies on published literature as much as possible but the team determined that new analyses were also needed.  The specific measures and emission estimates for use in developing this Assessment were selected using the International Institute for Applied System Analysis (IIASA) Greenhouse Gas and Air Pollution Interactions and Synergies (GAINS) integrated assessment model. New  simulations by two independent climate-chemistry-aerosol models were then produced by two models, one developed and run by the NASA-Goddard Institute for Space Studies (GISS) and the other was developed by the Max Planck Institute in Hamburg, Germany (ECHAM), and run at the Joint Research Centre of the European Commission in Ispra, Italy.
  • 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
  • More on the UNEP/WMO Assessment at

Contact details

David Garner
Senior Press Officer

Tel: +44 (0)1904 322153

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