“Some say the world will end in fire, some say in ice.”
– Robert Frost
Last month I wrote about positive feedback loops. Another name for these loops is â€œvicious circlesâ€. Their end result is often very destructive since a positive feedback loop can run out of control quickly.
An example of a positive feedback loop we all know is a sound system that squeals when the volume is turned up too high. Another example is what is happening to the ice pack in Greenland and to many glaciers. Being light in color, snow and ice reflect most of the sunâ€™s warmth. As the climate heats up, snow and ice melt exposing rock and soil underneath. Because of the darker color, they absorb more of the solar radiation which heats them up more, and so on.
In last monthâ€™s article I described six other positive feedback loops that all work to increase the planetâ€™s temperature. Several involve the greenhouse gases, carbon dioxide and methane. The sky-rocketing level of CO2 is the result of human activityâ€”from our profuse use of fossil fuels.
Thanks to careful monitoring since 1958, we know that the CO2 in the atmosphere has increased from 315 parts per million (ppm) to 380. The rate of increase of CO2 is even faster now than back in the 1950s. Furthermore, historic levels are significantly higher than any for the prior 650,000 years! How can we determine CO2 in the atmosphere from so long ago? Scientists measured the gas content of bubbles in Antarctic ice going back that far. Methane, 24 times as powerful in keeping in the sunâ€™s heat, is also rising dramatically.
The planetâ€™s temperature back in prehistory has also been estimated using isotopes of oxygen. If you compare a graph of those temperatures and a graph of CO2 concentrations, there is a strong correlation. It seems that the planet gets a fever whenever the CO2 level goes up! The greenhouse effect of CO2 (and methane) is the cause of this temperature rise.
Our time in the history of the earth is without precedent so no one can predict with certainty what the future will hold. Although our species has been around for a hundred thousand years, we have only been using fossil fuels in a big way for about 250 years. Never before has humanity faced the possibility that it has changed the planetâ€™s climate so radically.
Some predictions made by scientists are frightening. One model suggests that the climate will change even more drastically when atmospheric CO2 reaches 500 ppm. At the current rate of increase this will happen before the year 2100. Negative feedback systems now functioning limit warming. For example, as trees burn and release CO2, the smoke shades and decreases heat absorption. At 500 ppm those systems will be totally overwhelmed and the temperature will rise even more rapidly. Quite simply, we will bake. The world as we know it will no longer exist.
The prospect in the short run is also terrifying. If the average temperature rises just five degrees Celsius (9 degrees Fahrenheit), most of the temperate parts of the planet will become desert. This might happen about 2050, according to preliminary information from the Intergovernmental Panel on Climate Change. Not only will the climate become hotter, precipitation will diminish through much of the world. The subarctic, currently too cold to grow much, will become the most productive area in this future. There will be much less agricultural land in this scenario, and the growing season will be short. The saddest part of this model is that this rise in temperature will prove fatal to many millions of peopleâ€”perhaps even billions. They will starve to death.
Unless we change our course radically, the future looks frighteningly bleak. Fortunately I will be dead before the full consequences of global warming hit, but I cannot help but think of what will happen to my granddaughterâ€”and millions of other youngsters. This calamity is largely a consequence of my generation and others of the 20th century. We reproduced faster than in any other era of human history. And we enjoyed the pleasures of fossil fuel to the hilt. Unfortunately it is not we who will suffer the consequences, but our offspring. Our iniquity will go beyond the third and fourth generations.
It may already be too late to prevent this climate hell, but that doesnâ€™t mean that we shouldnâ€™t try. Averting global climate change will be the subject of next monthâ€™s article.
Â© Richard Grossman MD, 2006