BLACK CARBON

by Sir Crispin Tickell, Climate Institute Chairman Emeritus

August 31, 2009

In the last few years climate change in one form or another has entered public debate.  Of course global climate and local weather are always changing, but it is the idea that human activities, particularly since the industrial revolution, are responsible for dangerous and accelerating change, that is now causing alarm.  Successive Assessments of the Intergovernmental Panel on Climate Change have brought out the role of such greenhouse gases as carbon dioxide and methane in promoting global warming and climatic destabilization, but so far the importance of black carbon, otherwise known as soot, has  been underestimated.  This is now changing as a result of current scientific research, notably by V. Ramanathan at the Scripps Institution at La Jolla.

     Soot is usually associated with local pollution rather than global warming.  It comes from smoke arising from burning in all its forms, ranging from forest fires, power stations and cooking stoves to diesel exhaust from vehicles.  It has created the famous atmospheric brown cloud which, when seen from space, covers a lot of Asia, and sprinkles black droplets as far away as the Arctic and the Antarctic.  The science is far from simple or even certain.  Some of the components of black carbon can reflect solar radiation back into space, and therefore have cooling effects.  But in general it has warming effects, notably on ice and snow cover, whether at the Poles or along such mountain ranges as the Himalayas and the Andes.  It may reduce moisture in the atmosphere and thus affect patterns of rainfall.  The monsoon could be particularly affected.  It is also profoundly damaging for human health, particularly for those, usually women, who live by home cook fires in India and China.

     In the light of recent research it has been suggested that the warming effects of black carbon exceed those of all greenhouse gases except carbon dioxide.  Obviously many uncertainties remain.  But at least it should be a prime subject for discussion at the forthcoming meeting of the signatories to the UN Framework Convention on Climate Change (COP 15) at Copenhagen in December.  Unlike the effects of greenhouse gases which remain in the atmosphere for hundreds of years, reductions in black carbon could have effects within days or weeks.  

     It is never easy to attribute responsibility for black carbon emissions, but in global terms the largest emissions come from South and East Asia as a product of biomass burning, and in per capita terms from the United States, Europe and the OECD countries as a product of power generation and use of diesel in cars and heavy trucks.  There is obviously room for contentious debate at Copenhagen not only on responsibility for what is already happening but also on issues of human health.  We also need properly funded research to improve understanding of an especially complex set of issues.

     What then should be done if black carbon emissions are to be reduced?  There is the usual difficulty in fixing priorities.  They relate to most other issues at Copenhagen.  Obviously we need to tackle energy policy, reduce dependence on fossil fuels, improve energy efficiency and invest in new transport technologies.  We also need to ban or regulate slash-and-burn clearing of forests, limit combustion of agricultural and other wastes, and introduce new systems for home cooking stoves and heating.  Sequestration of biochar will also be important.  The list is long and connected with virtually all other environmental problems, including resource depletion, human population increase and migration, and loss of biodiversity.  

     Perhaps most difficult will be how to combine practical measures on the ground with distribution of financial help between countries.  In short, who should pay for what.  Still more important will be the creation of some institution to regulate and enforce whatever agreement can be reached.  My own view is that sooner rather than later we need a World Environment Organization to be the partner of the World Trade Organization, and coordinate the 200 or more environmental and related agreements which already exist.  Reduction of black carbon is too important to become the occasion for point-scoring in conference debate.  It is overwhelmingly in the interest of every country and every person in the world.  It is also a great opportunity for helping to avert what could otherwise be a climate tragedy of unknowable proportions.