At the C40 Summit in Sao Paolo last week, former President Clinton urged participating cities and the World Bank to make a dramatic reduction in methane and black carbon. He said it would help the earth buy some time on climate change. He has reasons to be worried: In Cancun last year, parties agreed  to stabilize average global temperatures at a level not exceeding 2 degree C above pre-industrial levels. This looks difficult as 0.8 degree C warming has already taken place and GHG emissions continue to grow.
Developed countries  collectively reduced greenhouse gas (GHG) emissions by a mere 6.1% from 1990-2008. Compared to the fast track for warming, humanity is on the slow train to reducing carbon dioxide (CO2) emission reductions.
President Clinton’s statement follows two recent reports that point to emerging scientific awareness that a climate change strategy focusing exclusively on carbon dioxide (CO2) is neither the quickest nor the most effective way to achieve long-term climate stabilization. These reports focus on non-CO2 emissions that stay in the atmosphere for a shorter period of time than CO2. As a result, reducing emissions of these non-CO2 gases will result in a slowing of temperature rise over the first half of the 21st century, buying time both to adapt and to transition away from carbon.
The first report , produced by UNEP and WMO, assesses black carbon and tropospheric ozone. Black carbon—basically soot—is produced by incomplete combustion of carbon fuels, particularly diesel, wood, and coal. It is a dark suspended particle or aerosol, technically not a GHG. It is frequently emitted together with light-colored aerosols (sulfates and organic carbon) which cool the climate. The latest research indicates that, on balance, the warming effect of black carbon overpowers the cooling effect of its companions. It stays in the atmosphere for only a few weeks before falling to earth. Its warming contribution comes from its black color, making it absorb heat while in the air. If it falls onto mountain or polar snow, it accelerates glacial melt.
The second report , published by Project Catalyst, focuses on potential reductions in climate warming by decreasing emissions of black carbon; methane; nitrous oxide (N2O); and fluorinated gases (F-gases). Methane and nitrous oxide are both GHG’s which are included in the UNFCCC and Kyoto Protocol. F-gases are industrial gases most of which are scheduled for phase-out under the Montreal Protocol.
Because of their short-lived nature and high global warming potential, these four emissions have a greater short-term impact on the rate of global climate change than does CO2. In 2005, they constituted 29 % of total anthropogenic emissions. Between now and 2030, they will account for roughly half of the anticipated global warming. Reducing these non-CO2 emissions will slow warming over the next 30 to 50 years, giving us time to agree upon how best to reduce CO2. Abatement for at least half of these non-CO2 gases will cost nothing or less than nothing, making a non-CO2 strategy very cost-effective.
The World Bank has a great deal of experience reducing emissions of non-CO2 climate forcers. The Global Gas Flaring Reduction Partnership  (GGFR) has identified the potential to reduce fugitive methane emissions. Projects supported by the Global Environment Facility  (GEF) and various development policy loans (DPLs) by the World Bank have focused efforts on utilizing methane from solid and liquid biological wastes. The Montreal Protocol has a strong history of working with refrigerator manufacturers to phase-out substances that deplete the ozone layer and also warm the climate. Recent estimates place the net climate change impact of the cumulative reduction of the World Bank’s Montreal Protocol at over 20 Gt of CO2 equivalent.
How can this new awareness of short-term climate forcers be combined into a program with almost immediate impact? How can we steer the Bank (and the world) back onto the fast track to a cooler world? I do not have the answers, yet. But the questions are worth pondering.