Monday, August 15, 2011

Advisors See Health & Climate Benefits From Black Carbon Mitigation

Aug 11: U.S. EPA's Advisory Council on Clean Air Compliance Analysis has completed its review of the draft EPA document, Report to Congress on Black Carbon, with respect to its accuracy and clarity in summarizing the available scientific literature, including uncertainties [See WIMS 3/28/11]. Black carbon is a mixture of light-absorbing particles that results from incomplete combustion of organic materials such as petroleum fuels or biomass, and these particles have been implicated in climate change and impacts on human health. In 2009, Congress directed EPA, in consultation with other Federal agencies, to summarize the available science on the impacts of black carbon on climate, sources of black carbon emissions, benefits to climate and human health from reductions in those emissions, and the cost-effectiveness of available mitigation strategies. The Council, augmented with experts in the chemistry, modeling and control of black carbon, has reviewed the draft 386-page EPA report and provides advice and recommendations in their own 74-page report.
    The Council indicates that it commends EPA on the quality of the draft report. In a cover letter to Administrator Jackson the Council indicates, "It is comprehensive and well-written, and summarizes much of the relevant scientific literature on the nature of black carbon particles; their formation, transformation and transport in the atmosphere; associated climate and health impacts; and possible mitigation technologies. In addition, the Report successfully uses text boxes and figures to convey a wealth of complex information. However, the enclosed Council report has many substantial recommendations for how the EPA report can be improved."
    The Council indicates that the preponderance of the available data support a conclusion that there are actions to reduce black carbon emissions that will be a -- "win-win" for public health and climate, and the Council urges the Agency to strengthen this message in the report. "The report should expand the discussion of health effects associated with black carbon, which is a component of particulate matter, and highlight the considerable health benefits that would derive from reductions in black carbon emissions. In addition, the Council recommends that the report be revised to include a more rigorous treatment of benefits and costs and associated uncertainties of black carbon mitigation options to inform policy."
    Without prescribing specific policies, the Council says, "the report should develop recommendations for U.S. black carbon mitigation strategies in the short and longer term, and strategies for developing countries, and discuss how the selection of metrics and mitigation approaches would vary for the different timescales and geographic domains.
    "The EPA report appropriately emphasizes that black carbon reductions should not be viewed as a substitute for needed reductions in long-lived greenhouse gases (including carbon dioxide and methane) over the long term, but is relatively silent on the unique benefits that might be expected from changes in more near-term influences. The Council recommends a more thorough discussion of these implications and the desirability of placing a higher priority on the control of a short-term climate forcer such as black carbon in addition to controls on long-lived greenhouse gases. In closing, the Council agrees that meaningful reductions in short-term climate forcers such as black carbon could provide additional time for society to implement climate change adaptation as well as to transition to low-carbon economies."
    Among the many recommendations, the Council's report indicates:

  • Based on the preponderance of available data, the Council suggests an affirmative statement that BC appears to warm climate and that BC mitigation will produce both health and climate benefits.
  • The Report should expand the discussion of health effects associated with BC, drawing upon the particulate matter, traffic emissions and other relevant literature, and highlight the considerable health benefits that would derive from reductions in BC emissions. This health co-benefit may exceed climate-mediated benefits.
  • The discussion of BC climate impacts should focus more on measures of climate response (such as changes in temperature and precipitation patterns), rather than on changes in radiative forcing, so that a broader set of impacts are considered and presented in terms that are meaningful to the generalist reader.
  • The Report should articulate potential benefits to pursuing a goal of reducing short-term climate change or slowing the rate of change, as a complement to the existing policy goal of limiting the long-term increase in global mean temperature. The discussion of metrics should discuss how policy goals will influence the selection of appropriate metrics.
  • The Report should discuss a broader range of BC mitigation approaches, including policies that could influence demand for sustainable transport, vehicle use generally, modal substitution, enhanced energy use efficiency, electrification using wind/water/solar, and improved fuel combustion and engine technologies.
    Access the Council's final report (click here)Access the Council website on the report and link to background, information on meetings and the 386-page draft report (click here). [#Air, #Climate]