When I moved here from Pennsylvania 11 years ago, this is what I was hoping winter would be like.  Maybe sweater weather in the morning and the evening, bracketing crisp, cool 55 oF afternoons.  Having been here for a while now, I know this year is not normal.  So what better time could there be for another column on global warming?  [Note: Of course, today as I finish this blog we have the first really cold day of the year.]
I touched on this topic after a long run of 100+ oF days, August last with “Welcome to the Greenhouse.” Here is the really short version of that previous post.  When sunlight hits the earth some of the energy is reflected back as infrared radiation.  The main components of the air, oxygen and nitrogen, do not absorb infrared radiation.  Therefore, if the air did not have other components which do absorb infrared radiation, this energy would be reflected back out into outer space.  Water and carbon dioxide do absorb infrared radiation, trapping this energy as heat in our atmosphere.  Without the Greenhouse Effect the global average temperature would be a chilly 0 oF rather than the current value of 57 oF.  The reason that you hear about carbon dioxide rather than water in regard to the Greenhouse Effect is that water cannot accumulate any more than it has in the atmosphere (when the air gets saturated with water it rains) but carbon dioxide concentration can grow essentially without limits.  Since the beginning of the Industrial Revolution, approximately 1850, the burning of fossil fuels has increased the carbon dioxide concentration of the atmosphere from 280 to 380 parts per million, resulting in an increase in global average temperatures of about 1.7 oF. 
The last United Nations conference on global climate was held in Copenhagen, Denmark in 2009.  The conference participants agreed to try to limit the global average temperature increase by 2050 to 3.6 oF above pre-industrial levels (that’s 1.9 oF above today) which corresponds to a carbon dioxide concentration in the atmosphere of approximately 450 parts per million.
The 450 part per million limit corresponds to the release of 1.4 more trillion tons of carbon dioxide.  That’s a big number and you might think that this sounds like a fairly reasonable limit to live under, right?  Here’s the problem.  And once you understand this problem you will know all that you need to know to understand the prospects for mitigating global climate change.  [Warning: The blog gets a bit pessimistic from here on out.]
If we burn the current proven fossil fuel reserves of coal, oil, and natural gas we will release 2.8 trillion tons of carbon dioxide into the atmosphere, twice the target from Copenhagen and enough to raise the temperature by 5 oF instead of the target of 3.6 oF.  Though no one knows for sure what the exact impacts would be of a 5 oF increase in global average temperature, we do know that sea level rise and changes in weather patterns would dramatically change our way of life, including regional famine, massive migration of people, and the submergence of most of the infrastructure built during the last 10,000 years of civilization.  As you can see, it’s sort of a big deal.
The question on the table is “What are the prospects that humanity will chose to leave half our remaining fossil fuel reserves in the ground?” Let’s consider the scenarios which might plausibly lead to this outcome.  Some may point to the growth in alternative energy sources like solar or wind.  When a new solar or wind facility comes on line, the press releases often make statements about replacing or deferring the need for traditional coal-fired power plants.  However, as far as I can tell alternative energy turns out to be additive to fossil fuel sources rather than a substitute.  Evidence suggests that our consumption of energy can, and will, grow to consume both traditional and alternative energy sources.  So my conclusion is growth in solar and wind energy will not end up reducing the amount of coal we burn or even significantly slowing the rate at which we do.  (Note:  I am specifically referring to coal here since wind and solar plants make electricity and so do coal fired power plants.  For more detail see “Electricity Production 101”)
Another plausible path to leaving half of our fossil fuels in the ground would be through collective action like that proposed in Copenhagen in 2009.  If you have been following similar efforts over the last several decades your optimism on this front will not be very robust.  There have been many conferences but no tangible results. You could hold out hope that in time the human tragedy meted out by global warming will lead to more concerted action.  The problem is that the primary consumers of fossil fuels, the U.S., Western Europe, Japan, and China, will not be among the first to suffer like Bangladesh, Sub-Saharan Africa, and Indonesia. I believe this dynamic will both slow the global response and be the primary driver of international conflict for the remainder of this century.
My view is that the two most plausible scenarios are:

  1. The combination of the effects of global warming and reduction in petroleum availability bring about a collapse of the global economic system.  This dramatically reduces industrial activity and the Copenhagen limit of 450 parts per million is achieved.  This will be a hollow victory because much of the progress of industrial civilization will be lost.
  2. The governments and peoples of the world work together sufficiently well to manage a smooth glide to a less fossil fuel dependent world.  In this case I believe it would be necessary to burn most of the remaining supply of fossil fuels as we utilized that energy to build the infrastructure we need for a lower energy existence thus bringing about the larger temperature rise of 5 oF and its ramifications.

Either of these two scenarios would necessarily lead to a world which had a human population of closer to 4 billion compared to today’s 7 billion.  It’s not yet clear which of these scenarios will play out.  Our grandchildren will know the answer.
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