Atmospheric Carbon:

The Plot Thickens

This week, the news carried several important items regarding carbon in the atmosphere, and by happenstance, I stumbled upon an additional items, so everything seems to be pointing me towards that as a topic for this blog.

Probably the biggest item to hit the streets was the fifth assessment report, or Synthesis Report, of the Intergovernmental Panel on Climate Change (IPCC).  The biggest soundbite to emerge from this report is that the IPCC calls for zero carbon emissions by 2100.  However, perhaps the most interesting element of the report for the nuclear community is that the report effectively says that a combined approach using all technologies is the best way to achieve this goal.  While it may be possible to meet the goal without one or more technologies, the cost of doing so will increase.

This, of course, fits in with what many responsible leaders have been saying for a long time, and reinforces the need to continue to develop and deploy a variety of energy technologies to meet future needs.

Perhaps coincidentally, this week also saw the release of a report that looked more closely at non-CO2 emissions and their behavior.  (The report, published in the Proceedings of the National Academy of Sciences, is co-authored by researchers from the International Institute for Applied Systems Analysis, IIASA, and the Potsdam Institute for Climate Impact Research.)

In particular, there had been some thought that limiting methane and soot emissions might be easier than limiting carbon-dioxide emissions and might limit the need to reduce CO2 emissions.  However, this study shows that reducing these emissions results in smaller benefits for long-term climate change than previously estimated.

The message here is a very mixed one, as a reduction in soot and other emissions would still improve the air quality, and would therefore yield benefits for human health and agriculture and near-term climate change, even if their contribution to long-term climate targets is less than previously presumed.  Also, other research has indicated that simultaneous and coordinated action on air pollution and climate change is more efficient, in terms of cost, than addressing each separately.

Finally, I was visiting Argonne National Laboratory (ANL) recently and picked up a copy of their latest journal, the Spring 2014 issue of Argonne Now.  Thumbing through the magazine, I found an interesting article that looks at different kinds of carbon particulates in the atmosphere, particularly "brown carbon" and "black carbon."  The article, which has the intriguing title, "The Volcano of A Hundred Thousand Mouths," appears on pages 26-29 of the print edition.  Because the PDF shows a two-page spread, the article is on pages 15 and 16 of the PDF.  (If you have an interest in future issues of their publication, ANL offers free subscriptions.)

Brown carbon comes largely from lower-temperature, smoldering fires, while black carbon comes from hot fires, such as from coal plants and car-engine combustion.  Although there is a lot more brown carbon in the atmosphere by mass, it can't trap heat as well as black carbon and therefore, has been largely ignored until recently.  Now, however, it is being recognized that brown carbon can be a significant factor in how aerosols affect the Earth's climate, and renewed attention is being given to this factor.

Taken together, the articles are a reminder of the huge complexity of the environment and what humankind is putting into it, and that the problems associated with fossil fuels extend beyond CO2.  All of this makes finding a realistic solution that much more difficult, but it also reinforces the importance of improving our understanding of the interactions of all energy-producing technologies with the environment as we move toward a new energy mix.

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