ericgrimsrud

The Paris Accord of December 2015 was a document produced by an international set of politicians and scientists. Science and politics are a rough mix.  The latter wants to solve the problem of climate change in a manner that does not change lifestyles and the former wants to solve the problem in accordance with the laws of physics, chemistry, and nature.  Given these profound differences we should not have expected much of a substantial nature to have emerged from this group – and, indeed, it did not.  Nevertheless, let’s have a careful look at what did emerge.

The primary goal envisioned in the Paris Accord is to limit Industrial Age global warming to 2.0 degrees C at least and to 1.5 C, if possible. In addressing these goals, however, was also recognized, at least by the scientists in attendance, that neither will probably be attained simply by reducing our emissions of greenhouse gases, including carbon dioxide, methane, nitrous oxide and tropospheric ozone.  In fact, it was generally recognized that within the very next decade or two we will have most probably emitted enough of these greenhouse gases as to cause temperature rises above 2.0 degrees C.  If those business-as-usual practices then continued further into the 21^st century, we would be headed towards a 3 to 6 degree warmer world.  Given those very possible occurrences, what were those delegates in Paris thinking when they signed off on this document?  That is, how could they suggest, with a straight face, that their goal is to limit future warming to 2.0 C and even 1.5 C?

The answer to that question is that they were assuming that by the second half of this century, we will have developed various means of man-caused “negative feedbacks” that counter and offset the man-caused “positive feedbacks” caused by our increased concentrations of greenhouse gases. In this case, a negative feedback is a change that would cause a cooling of the Earth. I suspect that the politicians in attendance might have bought into the reality of this term more than the scientists. In any case, these envisioned “negative feedbacks” were a part of the Paris plan but were not explained in any level of detail.

So it is now imperative that we understand what these negative feedbacks might be.  They would potentially be one of two possible types.  One would involve the  removal of the atmospheric greenhouse gases that cause global warming.  An example of such a technique would be to burn biofuels (i.e. wood) in power plants and then collect and bury the CO2 produced.  The great obstacles associated with such methods, however, are the sheer magnitude of these undertakings – rendering them financially untenable.

Another approach to man-caused negative feedback is via solar radiation modification (SRM) by which a larger portion of our incoming sunlight would be reflected back into outer space. Mother Nature already does this, of course.  About 30% of incoming solar radiation is naturally reflected (we call this fraction the “albedo” of the Earth) off reflective surfaces including highly reflective clouds and snow.  Because some of these SRM techniques are expected to be less expensive than greenhouse gas removal they seem to be receiving most of our attention.

Among the envisioned methods of sunlight reflection, the one that appears to have received the most attention so far is illustrated in the following figure which shows how Mother Nature and potentially mankind can cause this reflection via the formation of sulfate particles in the Earth’s stratosphere.

Whenever unusually powerful volcanic eruptions occur – such as that of Pinatubo in 1991- gaseous sulfur dioxide (SO2) is punched very high into the Earth’s stratosphere. Simultaneously, that sulfur dioxide is oxidized to involatile forms of sulfate that condense into particles.  An increased fraction of the incoming sunlight will then be reflected off those particles.  This, of course, will tend to cool the Earth.  For example, the Pinatubo eruption cooled the surfaces of the Earth by about 0.1 degrees C for two years after that single eruption. This cooling effect lasted for two years because it takes that long for small particles to be removed from the stratosphere by the pull of gravity. Thus, a predetermined amount of SO2 continuously added to the stratosphere could have a significant and long-lasting effect on the Earth’s surface temperatures.  The amount of SO2 injected and the magnitude of its cooling effect could be continuously adjusted as needed in order to obtain the average global surface temperatures desired.

As illustrated in the figure, gaseous SO2 could be emitted artificially into the stratosphere either by hydrogen-filled balloons as shown or by high altitude aircraft. By the same subsequent reactions as describe above, this would cause increase refection of sunlight and continuous cooling of the Earth. The fact that this process is expected to be relatively inexpensive seems to have given it the inside track among the man-caused negative feedback methods being considered.

But wait a moment, all means of climate modifications, including this one, have various potential downsides that must be very carefully considered before implementation on a large scale. Concerning the addition of SO2 into the stratosphere, these concerns include the following.

The Earth’ s stratosphere is a fragile region of our total atmosphere in which various chemical processes perform functions that are vital to what happens below and on the surface of our planet. In particular, incoming and otherwise deadly ultraviolet (UV) radiation is removed by stratospheric ozone (O3) and the concentration of O3 in the stratosphere can be diminished by the presence of other chemical substances artificially added to the stratosphere. This, for example, is what happened when mankind added chlorofluorocarbons (Freons) to the atmosphere – eventually leading to ozone loss and a ban on the use of CFCs. So we need to know how much damage, if any, would SO2 and its oxidation products do to the ozone layer if made long-term components of the stratosphere.  In addition, what would these added sulfate particles do to weather patterns throughout the Earth? And what might they do the stratospheric clouds in Antarctica that have been implications in formation of the “ozone holes” now annually observed there? In other words, would we really want the equivalent of a Pinatubo continuously blowing sulfate debris into the stratosphere?  We don’t know the answer to that question yet and would certainly want to know it before we implement this method on a grand scale.  This is an example of revealing “unintended” consequences – as we failed to do prior to our massive production and use of chlorofluorocarbons.

Another problem raised by this and other SRM plans are that they do not address the acidification of our oceans that is occurring due to increasing levels of atmospheric CO2. This problem is perhaps just as detrimental to forms of life in the seas as temperature increases are to those on land.  Ocean acidification would actually be enhanced by any SRM method that simultaneously allows CO2 levels to increase. Thus, it appears that eliminating the CO2 emissions of mankind would be the only way to address both of these problems.

Another issue sure to occur with intentional modifications of climate and weather would be of an international political nature. The nations of the world would certainly have different opinions concerning their choice of an “ideal” climate.  The country of Pakistan, for example, has been suffering from extreme weather events (flooding and warming) as a result of man-caused warming.  At the same time, some countries to their north, such as Russia, might not be so interested in lowering their average temperature.  Climate changes could cause some large regions with moderate levels of rainfall to become non-arable deserts. The great difficulties to be expected in making these command decisions at both national and the international levels cannot be overstated.

Finally, another problem associated with all methods of artificial climate modification is that they give the public the impression that “something can be done” about it leading to the conclusion that “we can fix it later” which, in turn, decreases our efforts to cut greenhouse gas emissions. This is a potentially fatal set of thoughts because we do not know if any of these envisioned negative feedback schemes will work satisfactorily. They might even cause greater environmental problems due to their unintended consequences.  And lastly, we only have one planet on which to perform these “experiments”.

I hope you now have a better understanding of the unsubstantiated assumptions inherent of the Paris Accord’s envisioned plan for addressing global warming. You might also now understand why I consider these climate modification plans to be unwarranted at the present time. The fact that these ideas constitute a major element of the Paris Accord suggests to me that too many of our political and scientific leaders are willing to reduce public angst today concerning this problem by passing the solutions to the problem off to the next generation. In this way, we continue to “feed the beast” (that is, our ultrahigh carbon lifestyles) and ignore our intergenerational responsibilities.  Sure, something will come up, right?  And in the meantime, “talking the talk” should be enough to be a credible member of our generation, right? !!  Unfortunately, politics and science might not turn out to mix at all well.