Clearing the Air About Clear Skies and Climate
London, clear skies. (Photo: istock / V. Zolotov
Beautiful blue skies from the “coronavirus lock-down” have been stunning in most major cities, due to the lack of cars and trucks. Improvements to air quality and respiratory problems were immediately apparent. Unfortunately there has been some misunderstanding about the relationship with climate change. We need to clear the air about some common confusion between carbon and carbon dioxide; between visible air pollution and clear greenhouse gasses.
Visible air pollution in the form of black smoke, smog, and visibly “dirty-air” is largely carbon particles. Carbon is of course a chemical element, normally black, as in the pure powder form, and essentially in pure forms of coal. (Paradoxically, carbon can also be clear, as in the crystalline form of diamonds, created under enormous pressure.) If we can find ways to continue to reduce the amount of that particulate carbon pollution in the air (as well as nitrous and sulfur oxides) it would have a huge benefit on human health, particularly related to respiratory problems.
In contrast, the primary cause of global warming, or climate change, is the increased greenhouse gases that trap heat in the atmosphere. Those gases are completely clear. The gas over which we have the greatest control is carbon dioxide, “CO2”, a by-product of burning carbon-based fossil fuels. More than a century ago, clear carbon dioxide was proven to trap heat. Before the industrial era and vast burning of fossil fuels, CO2 was at 280 ppm (parts per million); during the ice age cycles it was as low as 180 ppm. After decades of burning fossil fuels, the level has reached 418 ppm in 2020. That elevated carbon dioxide level correlates with the overall planetary warming.
One of the reasons for the confusion between black carbon air pollution and clear carbon dioxide emissions is that even scientists and environmental advocates have taken to describing the removal of carbon dioxide from the atmosphere as “removing carbon” as a shorthand for carbon dioxide. Regardless of any atomic equivalence, they are completely different. [You may recall from chemistry in school that one atom of the black element carbon combines with two atoms of oxygen to become clear carbon dioxide, an entirely different molecule. Molecular compounds have different characteristics than the elements from which they are created. Another similar example of compounds having different properties than elements is the two clear gases of hydrogen and oxygen that transform into liquid water, H2O.]
In addition to the dramatic reduction in visible air pollution, the coronavirus lock-down has caused a slight reduction in the rate of carbon dioxide emissions. That will slow the rate of warming a little.
Unfortunately the reduction of the visible air pollution, actually has a warming effect. Those visible particles in the atmosphere actually reflect sunlight. So the clear skies which are very welcome in terms of clean fresh air, better breathing, and beautiful vistas, actually will add a little bit of warming in the short term.
If we are going to advocate good policy and solutions, and educate others, we need to blow away the smoke and be crystal clear. Visible air pollution and the invisible greenhouse gases are entirely separate issues. Fortunately, the shift to “green” renewable energy sources is a path to reduce both the carbon-based particulate matter causing visible air pollution –– and the clear carbon dioxide, causing the planet to warm.