Drilling down on fossil-fuel burning and its connection to carbon, carbon dioxide in air

So, fossil fuels: what are they?

Fossil fuels get their name from substances created from the process of anaerobic decomposition of dead, buried-in-the-ground organisms (matter) that provide energy when burned, according to the online encyclopedia Wikipedia.

Secondly, with the igniting of fossil fuels and with the quantities burned, the thinking is, such has contributed to a changing climate and warming world.

It’s a cause-and-effect relationship and, as we shall see, more than a slightly complicated one at that.

The problem

It was in “Black carbon and climate change: Research suggests link” that I elucidated on the physical connection between atmospheric carbon and climate change.

Part of what I wrote was this: “… characteristic of black carbon is its ability to absorb sunlight rather than to reflect it, thereby making it a warming pollutant. Meanwhile, combined with a host of other polluting particles, some having a cooling effect, when all things are taken into consideration, though, on the whole the overall net effect is atmospheric warming, confirmation of such ‘based on both observations and computer modeling.’ This is what I understand to be the case.”

It’s a pretty straightforward premise. But, how do we know for sure whether or not the impact of black carbon on the air involves more than just atmospheric warming and is a contributing factor in a changing climate?

This is the question that I seek (and hope) to find an answer to. As it has to do with that, I’ve referenced the Black Carbon and the Regional Climate of California – Report to the California Air Resources Board document, to try to break this down.

BC, OC and RF

Starting from the start, some terms with which to become familiar: Black or elemental carbon (BC, EC), brown or organic carbon aerosols (BrC, OC) and radiative forcing (RF) which also goes by the name “solar absorption.” All solar absorption (or radiative forcing) means is that sunlight either traveling to Earth or that which has been reflected by the Earth’s surface heading back out into space, gets absorbed, such as carbon dioxide in the atmosphere or ozone in the stratosphere do, just two examples. EC and OC, meanwhile, will be explained in greater detail a little farther on in this post.

From the report is the idea that the black carbon component of diesel particulate matter, if this were reduced in the atmosphere, this could lead to atmospheric cooling.1

But, what of the opposite – atmospheric heating? What effect does BC have on that?

From the Black Carbon and the Regional Climate of California report in the “Importance of Brown Carbon for Solar Absorption” section, Veerabhadran Ramanathan, et al. write: “Analysis of the spectral dependence of solar absorption, measured in-situ as well as over the column, indicates an enhanced absorption at shorter (<500 nm) wavelengths that deviates from the expected behavior of BC. This enhanced absorption is attributed to organic, ‘brown’, carbon. The solar absorption due to brown carbon is found to contribute as much as 40% of the BC forcing in the near-UV (<440 nm) wavelengths. Field measurements in several independent campaigns using aethalometers for absorption, and the ATOFMS [Aerosol Time of Flight Mass Spectrometry] for detailed chemical analysis find that brown carbon is primarily related to residential wood burning. However, a new class of particles related to secondary organics, i. e., aged large organic particles, is also found to contribute to solar absorption, thus raising the possibility that fossil fuels also contribute – via their contribution to secondary organic particles – to brown carbon absorption. We find that the direct warming effect of brown carbon, ignored in most models, offsets about 60% to 90% of the direct cooling effects of other organic carbon aerosols.”2

Black and brown carbon further explained

So, black and brown carbon – what are they, exactly? Ramanathan, et al. in the Black Carbon and the Regional Climate of California report provide detailed definition information for each.

Black Carbon (BC): Soot contains black carbon and organic carbon aerosols, which absorb and scatter solar radiation and thus impacts the climate system from local to regional and global scales. The component of soot that absorbs solar radiation is usually referred to as black carbon (BC) or elemental carbon (EC). The two terms, BC and EC, are used interchangeably and we follow the same practice in this report. … In principle, the relatively strong light absorption properties of BC can be used to infer BC from an optical measurement and knowledge of the mass specific absorption of BC. In thermal methods, the filter media used for sample collection is heated and the thermally evolved carbon in the specified temperature plateau and analysis atmosphere defines the concentration of EC and organic carbon (OC).”3

Brown Carbon (BrC): Organic carbon is normally assumed to be a pure scattering aerosol. However, recent experimental studies have demonstrated that a fraction of OC also absorbs sunlight with their absorption increasing dramatically towards shorter wavelengths (<500 nm wavelengths). The absorbing part of OC referred to as brown carbon. In this report, the term OC includes BrC.”4

A carbon, carbon dioxide disconnect?

We so often hear or read about carbon dioxide or the concentration of carbon dioxide in the atmosphere. There obviously is so much to try to keep straight about carbon and carbon dioxide in one’s own mind.

Oil shale combustion

What I have learned is that oil and coal, for example, are carbonaceous substances meaning they contain carbon. They are also considered fossil fuels, presumably, because they are fossilized materials that when burned produce energy while at the same time releasing carbon.

It is through burning of aforesaid carbonaceous substances that carbon is released and when that and air (oxygen) combine through a chemical reaction, that is how carbon dioxide from said releases is formed.

Remember: Carbon in the atmosphere, any way you look at it, is a pollutant is a pollutant is a pollutant is a pollutant.

Notes:

  1. Veerabhadran Ramanathan, et al., Black Carbon and the Regional Climate of California – Report to the California Air Resources Board, “Executive Summary,” Apr. 15, 2013, p. 20
  2. Ibid, “Abstract,” pp. 18, 19
  3. Ibid, “Executive Summary,” p. 20
  4. Ibid

Image (top): California Environmental Protection Agency Air Resources Board

This post was last revised on Oct. 7, 2018 @ 8:50 p.m. Pacific Daylight Time.

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