Al Gore’s latest book – Our Choice: A Plan to Solve the Climate Crisis – includes a fair bit of discussion of black carbon, a human pollutant that causes global warming, but not in the same way carbon dioxide (CO2) does. Greenhouse gasses like CO2 prevent long-wave infrared radiation from leaving the Earth into space. Black carbon, by contrast, warms the planet by absorbing a lot of short-wave radiation from the sun. In essence, it has a very low albedo.
Some other pertinent things to know about black carbon:
- The largest source is biomass combustion – such as burning forests and grasslands to clear them for agriculture.
- The areas where this is happening most are Brazil, Indonesia, and Central Africa.
- Black carbon settling in the Arctic is a major cause of warming there: possibly responsible for 1Â°C of the 2.5Â°C of warming already observed there.
- Black carbon is also a major threat to Himalayan glaciers, which in turn provide the source water for rivers of critical human importance, such as the Ganges.
- Black carbon is washed out of the atmosphere by rain, and only has a lifetime of a few weeks. If we stopped emitting it, its contribution to climate change would cease quickly.
The last of those is very encouraging. Unlike CO2, which remains in the atmosphere for a very long span of time, black carbon is something we could tackle on a short timescale, by mandating things like filters on diesel engines and the cleaner burning of coal and biomass.
As mentioned before, recent research has also highlighted the importance of non-CO2 greenhouse gasses. Anything that allows us to take more rapid and effective action to halt climate change is welcome news. Also, it requires a lot less political will to install better filters on diesel engines than it does to curb activities that are critically linked to greenhouse gas emissions.