Limiting Near-Term Climate Change While Improving Human Well-Being

Emissions of black carbon and tropospheric ozone precursors affect human well-being in many ways, altering climate and degrading air quality. Hence there have been many suggestions that in principle, control of these emissions could be a useful way to mitigate near-term climate change and improve human health. The 2011 UNEP Assessment has quantified the potential impact of specific, practical emissions control measures that could be implemented with current technology or behavioral changes. We find that globally, these measures can substantially mitigate near-term global warming, increase world food supplies, and reduce premature mortalities due to outdoor air pollution.

Sustained implementation of the selected measures between the present day and 2030 will decrease near-term (20-30 years) global and regional warming. This would reduce global warming by 0.4 +/- 0.2 ^oC by around 2035 compared to a reference scenario based on current trends and agreed legislation. The implementation of the selected measures in this assessment will lead to a particularly large benefit in the Arctic, reducing warming there by 0.7 +/- 0.5 ^oC by around 2040 compared to the reference scenario. The warming from BC and O₃ has strong regional variations that can lead to substantial regional climate impacts. For example, large regional heating from absorbing particles can disturb regional circulation patterns such as the Asian Monsoon. Hence much of the climate benefit of emissions reductions would be felt locally.

Millions of premature deaths and the loss of tens of millions of tons of crops would be avoided each year resulting from reductions of small particulate matter (PM_2.5) and ozone concentrations by implementing the selected measures, in comparison to the reference scenario. The economic valuation of the health and crop yield benefits from implementing the selected measures would amount to trillions of US dollars annually. Even more so than with climate, the benefits of improved air quality will be felt most strongly in the places where emissions are reduced.

The measures examined here are already mature technologies with demonstrated results at scale in the real world. Many of the structural changes examined here present formidable hurdles to implementation, however. Efforts to scale up, replicate and expand the implementation of the selected measures could include capacity building, public-private financing, technology support, regional cooperation and agreements and community empowerment.