Black Carbon and Global Warming

There is a new, climate change villain in town. Let’s say that this villain is not necessarily new but it has been elevated to a new level of importance and visibility.

Whenever we speak of global warming and climate change, the most guilty contributor always seems to be CO2. It deserves to remains in the top spot. Unfortunately, the second most significant contributor to global warming is not quite as common in our everyday language – but should be. It is known as “black carbon”.

Unlike petroleum (black gold), black carbon is not an asset. It is a liability from the excessive burning of carbon-based fuels. Some fuels are “cleaner” than other fuels. I challenged your thinking about clean fuel in an earlier post: “An Ear of Corn. Natural Gas…

Black Carbon is about the fuel residue that floats around in the atmosphere. It has numerous sources of origin. From a recently published (and highly technical – way beyond my level of science comprehension) geophysical study: Bounding the Role of Black Carbon in the Climate System: A scientific Assessment, the most likely sources of black carbon emissions are:

“Black Carbon Emissions and Abundance
Sources whose emissions are rich in black carbon (‘BC-rich’) can be grouped into a small number of categories, broadly described as diesel engines, industry, residential solid fuel and open burning. The largest global sources are open burning of forests and savannas. Dominant emitters of black carbon from other types of combustion depend on the location. Residential solid fuels (i.e., coal and biomass) contribute 60 to 80% of Asian and African emissions, while on-road and off-road diesel engines contribute about 70% of emissions in Europe, North America and Latin America. Residential coal is a significant source in China, the former USSR and a few Eastern European countries. These categories represent about 90% of black-carbon mass emissions.”

In 2009, WIlliam Lau (NASA Goddard Space Flight Center Atmospheric Sciences) concluded a study about the impact of atmospheric aerosols. Should we care about who is burning what around the world? Should the rest of the world be concerned about our vehicular emissions? Yes, to both.

“A new modeling study from NASA confirms that when tiny air pollution particles we commonly call soot – also known as black carbon – travel along wind currents from densely populated south Asian cities and accumulate over a climate hotspot called the Tibetan Plateau, the result may be anything but inconsequential.

His research reinforces with detailed numerical analysis what earlier studies suggest: that soot and dust contribute as much (or more) to atmospheric warming in the Himalayas as greenhouse gases. This warming fuels the melting of glaciers and could threaten fresh water resources in a region that is home to more than a billion people.

He also discovered that these heat-absorbing aerosols, when spun together with warm air currents and moisture, cause a heating effect in the air that triggers the rainy period earlier than usual, lengthening the monsoon season in Asia.”

All climate and weather is determined by the movement of atmospheric winds. They circulate the heat from the tropics and the cold air from the Poles. They travel in alternating directions – depending on their latitude. That means that emissions reaching the high atmospheric levels are transported around the globe and will eventually affect each continent. This can be easily viewed in this global wind pattern map.

North America is impacted by winds that come from Asia to Alaska, down and across the country from West coast to East. We are also impacted by the equatorial winds that originate in West Africa.

“West Africa is the largest global source of atmospheric dust owing to an abundance of deflatable materials and strong low-level winds and most dust generated in West Africa is advected over the tropical and subtropical North Atlantic.”

The aerosols from West Africa are both good and bad. They contain mineral-laden particles that are deposited over the land. These can improve soil quality. They also form a thin layer on the surface of the Atlantic Ocean that NASA studies also believe has a cooling effect on ocean temperatures and may reduce the frequency and intensity of hurricanes and tropical storms.

Not only are these aerosols affecting the onset and duration of the Asian monsoons, but the “heat pump” effect of atmospheric aerosols is also affecting rainfall in South America and West Africa.

Unfortunately, black carbon is here to stay. As the global population continues to rise – and most of that is expected to be in developing countries, there will be an even greater increase in atmospheric aerosols than we have today.

Whether you are burning a cooling fire in India or Africa or driving a diesel vehicle in the US and Europe, the soot that is being emitted is black carbon. We’ve got a lot of work that remains to be done in cleaning up our environment.

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