The impacts on global climate change on the environment are often difficult to predict or imagine. New research, however, offers a glimpse as to how dramatic such changes have the potential to be.
According to Atlantic magazine (Oct. 16), new climate analysis methods prove that the Sahara Desert rapidly transitioned from a Serengeti-like environment into the most arid region on Earth about 5,000 years ago.
Researchers, led by Jessica Tierney and Peter de Menocal, analyzed decaying hydrogen and carbon isotopes in fossilized leaf wax buried in ocean sediments near the Horn of Africa to document the climate of the region during the past 20,000 years. The advantage of using such a method is that ocean samples are less susceptible than land samples to degradation by chemical and geological processes.
The most stunning find of their research is that this once-humid area became a vast desert in only 100 to 200 years, a relatively swift transformation on a geological time scale. Scientists believe this brisk transition was the result of positive feedback loops. The implications of this research are alarming; if desertification occurred so swiftly in the Sahara, how dramatically could today’s world be altered, given the current trend of global warming?
Positive feedback loops in the environment will likely play a large hand in the near future, regardless of the causes of contemporary climate change, be they human induced or naturally driven. A positive feedback loop is created when the effects of a system are enhanced by the products of that system. For example, earning interest on a savings account and then saving that interest to earn more interest is a positive feedback loop.
In terms of climate change, melting ice caps constitute a major positive feedback loop. When ice in the Arctic melts faster than it is replaced the following winter, less sunlight is reflected, and an increasing amount of darker land or ocean is exposed to sunlight, causing further warming and increased melting of the ice.
Another example of positive feedback is the melting of permafrost. According to a New York Times article (Dec. 16, 2011), there are about 1.5 trillion tons of carbon frozen in permafrost in the Arctic tundra, which is around two and a half times as much carbon currently present in the atmosphere. As the planet gradually warms, the permafrost thaws, releasing carbon dioxide and methane into the atmosphere. Given that these are both greenhouse gases, their presence in the atmosphere will exacerbate the melting of the permafrost, releasing even more carbon into the atmosphere.
Other positive feedback loops exist, including potentially unknown ones, but the lesson is unmistakable. To avoid the dangerous effects of positive feedback, it is best to make an effort now to slow climate change rather than risk the dramatic change the Sahara underwent 5,000 years ago.
Alex Waheed is an Oak Park resident.
