For much of the past twenty-five years, efforts to control global warming through limiting carbon emissions have mostly involved an economic fight, which the carbon producers have won.
Oil and coal companies today are as economically powerful as ever, and are still preventing all but the smallest tentative steps towards real and effective control of carbon.
However, the stakes may be more than economic. A new paper published in the Proceedings of the National Academy of Science suggests that for many mid-range global warming scenarios, the average global temperature will rise above what humans can survive.
Human core body temperature is around 37 degrees C., and skin temperature around 35 degrees C. In order to avoid lethal overheating of the body's core, humans cannot endure for more than 6 or 7 hours external temperatures above 35 C. To see how close we are to that temperature today, and what realistic scenarios may be in the next century follow below the ominous squiggle of extinction.
The paper titled An adaptability limit to climate change due to heat stress, was written by Steven C. Sherwood of University of New South Wales, and Matthew Huber, of Perdue University.
They first established the temperature at which the human body succumbs to lethal overheating, which is around 35 degrees C. They then measured the land area affected with these temperatures for significant periods of time, i.e. weeks or months, under the commonly accepted scenarios for continued global warming.
Peak heat stress, quantified by the wet-bulb temperature TW, is surprisingly similar across diverse climates today. TW never exceeds 31 °C. Any exceedence of 35 °C for extended periods should induce hyperthermia in humans and other mammals, as dissipation of metabolic heat becomes impossible.
While this never happens now, it would begin to occur with global-mean warming of about 7 °C, calling the habitability of some regions into question. With 11–12 °C warming, such regions would spread to encompass the majority of the human population as currently distributed. Eventual warmings of 12 °C are possible from fossil fuel burning.It is important to note that once carbon is in the atmosphere, warming does not stop when the emissions stop. There is a lag effect of several hundred years until the climate reaches a new equilibrium.
What Sherwood and Huber are saying is that each doubling of the amount of CO2 in the atmosphere leads to a temperature rise of around 4.5 °C.
If we allow the profiteers to burn the carbon reserves they currently own, total warming in 300 years would lead to 2.75 doublings of CO2, or a global temperature rise of about 12 °C.
There are also feedback effects to consider, such as the outgassing of methane in arctic soils as permafrost melts, and possible destabilization of methane hydrates on the continental slope.
So, while the business as usual scenario is thought to lead to a 4 to 5 °C rise in temperature at the end of the century, a couple of hundred years later it could easily be over 12 °C.
At that temperature, much of the earth becomes uninhabitable for humans and other large mammals, and we go extinct.
The authors say that most current thinking about the worst case scenarios are based on
economic costs extrapolated from present-day data,
but this is clearly unsatisfactory for climates so different from any in human experience. Inability to specify consequences of very large warmings is therefore a hurdle to rational decision-making on climate mitigation.Most people think that because we can tolerate a wide range of temperatures today, we can adapt if the temperature was warmer. But this is not true. There is an upper limit, and we are surprisingly close to it.
We show that even modest global warming could therefore expose large fractions of the population to unprecedented heat stress, and that with severe warming this would become intolerable.So we are not just facing a crisis of sea level rise and extinction of many species due to loss of habitat. Continued burning of carbon is literally the path to our own extinction as a species.
Our capitalist system is built on allowing people like the Koch Brothers and other oil, gas and coal owners, to extract huge profits today based on imposing huge external costs on other people in the future. So long as those people are poor, brown, and invisible there is no outcry.
But would you be complacent if you were told your great grandchildren would be part of the last generation of humanity.
I have been a climate activist, but until reading this paper, I never actually considered that Exxon and other companies could cause the extinction of the human race.
When I was going to school in the 1950's, we lived with the knowledge that we all might die in a nuclear holocaust. I remember reading Nevil Shute's On the Beach - a story of the last six months of humanity.
The plot involved the crew of a submarine that made it to Australia, as lethal radiation slowly spread to the southern hemisphere, and everyone knew that within six months they would be dead. The novel was about how ordinary people's daily lives could be in the face of unchangeable catastrophe.
That sense of possible doom was really present. Another high school paper I wrote was about the last couple on earth - except the woman was pregnant. The story ended with the mother's death in child birth, and the father's delivery of a son. Very adolescent stuff.
When I first read Sherwood's paper, I thought if everyone knew this there would be immediate calls for eliminating carbon fuels.
But then I remembered that in the 1950's we just accepted the idea of nuclear annihilation as something we grew up with; that was the way the world was and the number of people who protested - who felt this was an intolerable situation - was very small.
So, I think we need to add this information about our own extinction to our conversations, and explain the risks and costs of not acting on carbon. But just the facts are not sufficient.
The emotional pull is stonger. Why should I contemplate the destruction of everything I have ever loved, along with the sweep of history I find so moving and revealing, so that a criminal oligarch can extract more money for another decade or two.
This is the emotion of revolution.