I am writing to report about new research and publications related to black carbon emissions from kerosene lighting. The short story is that the climate change mitigation benefit of successful efforts to replace kerosene lighting with cleaner alternatives is much larger than previously understood. Prior analyses have  focused on the climate change impact associated with carbon dioxide emissions from kerosene consumption, but they have not included the climate change forcing caused by the black carbon particulates that are emitted when kerosene is burned in a lamp. 

A recent analysis published in December in the Environmental Science and Technology journal (Lam et al., 2012) quantifies the climate change impact of black carbon (BC) emissions from kerosene lighting. The results show that simple wick lamps are a major source of black carbon. The climate change forcing of BC from simple wick lamps is on the order of 20 times the effect of the carbon dioxide emitted from burning the same kerosene. The BC emissions from hurricane lamps and pressure lamps is much smaller because they burn the kerosene more efficiently. If all sources of kerosene combustion for lighting are considered together, the aggregate climate change impact of the black carbon emissions appears to be on the order of five to 15 times the climate change impact of the CO2 emissions alone.

These results are summarized and discussed in a short article that was just published through the Brookings Institute (Jacobson, et al., 2013). The article, which is co-authored by Nick Lam, Tami Bond, Nathan Hultman, and me, presents a summary of the climate change impacts of BC emissions from kerosene lighting along with a discussion of steps that can be taken to address the issue. This summary piece is meant to be more accessible than the original scientific article, so it is a good place to start for those interested to learn more about the topic.

I will additionally offer a few thoughts on the topic here:

1)    Reductions in black carbon emissions offer an early opportunity to make a near term difference for climate change mitigation. Carbon dioxide has a long residence time in the atmosphere, which means that today's reductions take decades to provide a substantial positive benefit. In contrast, black carbon has a very short residence time in the atmosphere - just a few weeks. This means that near term reductions provide an immediate climate change mitigation benefit. Mitigation requires reductions on all fronts, but BC reductions are a very good way to make a near term difference.

2)   As noted above, simple wick lamps represent the primary source of black carbon emissions from kerosene lighting. Hurricane and pressure lamps produce far fewer BC emissions because the burn the fuel much more efficiently. One of the big uncertainties associated with current estimates of the climate change impact of kerosene lighting is a lack of reliable data about the fraction of kerosene lamps that are simple wick and the fraction that are the hurricane or pressure types. Better data about burn rates for the various lamps used around the world are also needed. Careful studies that document lamp types and burn rates in countries where kerosene lighting is common will go a long way toward improving understanding of the climate change impact of kerosene lighting and the opportunity to mitigate it. Candles may also be a significant source of BC emissions, and work to document their emissions and prevalence is also valuable.

3) The Clean Development Mechanism and other leading carbon credit schemes do not yet offer credits for the reduction of black carbon emissions. As a result, it is not possible to earn credits (and revenue) from verified reductions in BC emissions. However, BC could potentially be added to the list of pollutants covered under carbon credit schemes in the future. If and when this happens, the resulting revenue from measures to replace kerosene lighting with cleaner alternatives will increase dramatically (though the actual revenues will depend on the carbon credit price, which is currently very low). 

4) Recent scientific work on black carbon published by the American Geophysical Union (Bond, et al., 2013) indicates that BC is very likely the second most important pollutant contributing to climate warming. This report focuses on a number of black carbon emissions sources ranging from forest fires to diesel engines and many others. See http://www.agu.org/news/press/pr_archives/2013/2013-01.shtml for more information.