Part 1: The evidence
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By William C. Shelton

(The opinions and views expressed in the commentaries of The Somerville Times belong solely to the authors of those commentaries and do not reflect the views or opinions of The Somerville Times, its staff or publishers)

Storm after storm, my neighbors and I gathered to shovel snow with grudging good humor. Occasionally I heard someone question how the planet could be warming while much of the country was in a record-setting deepfreeze.

In fact, global temperatures last year were the fourth hottest in recorded history, and we were freezing because of it. Rising temperatures had broken down the polar vortex that keeps frigid air in the Arctic, allowing it to move to temperate latitudes, while providing more data on climate change.

Last week the Intergovernmental Panel on Climate Change released the third and final report of its fifth update. Some 800 scientists, along with representatives from 200 countries, collaborated for seven years on this update.

Its first report, issued in December, was “The Physical Science Basis.” It showed that climate change will soon be irreversible.

The same month, a National Academy of Sciences study warned of looming “tipping points” beyond which “major and rapid changes occur.” And last month in a report entitled “What We Know,” the American Association for the Advancement of Science stated that “…human-caused climate risks abrupt, unpredictable and potentially irreversible changes.”

As chilling as the IPCC’s forecasts may be, they are conservative. Their 1990, 1995, 2001, 2007, and current updates each showed changes happening more rapidly than the previous update had anticipated. One would expect such conservatism from scientists, but especially so when political representative from as many as a hundred governments must agree, line-by-line, before a report can be issued.

Outside these political constraints, a majority for the 97% of climate scientists who say that human-made climate change is real and threatening, also believe that threat is greater and more immediate than the IPCC states.  A December journal article by NASA’s James Hansen and 17 of his climate colleagues argues that the IPCC’s goal of limiting global temperature rise to 2° Celsius will not forestall disaster. Instead, increases above 1° C will produce catastrophic outcomes.

Then there are climate scientists who offer credible evidence that even moderate increases can trigger an event cascade that destroys civilization. This scenario is based on greenhouse gasses now contained as hydrated carbon and hydrated methane.

Carbon and Methane are the two primary greenhouse gases. About half of earth’s organic carbon is trapped in permafrost, less than ten feet from the surface. Methane is 23 times more powerful a greenhouse gas than CO₂ on a 100-year timescale; 105 times more potent on a 20-year timescale. Gigatons of methane are trapped within frozen undersea clathrate beds and permafrost.

Because the ice that once reflected sunlight is melting and the ocean is absorbing heat, the Arctic is warming faster than any other global region. U.S. Navy researchers predict it will be ice-free by 2016. Meanwhile, a Nature Geoscience study finds that as many a million tons of methane are already bubbling up like seltzer across two million square kilometers of East Siberian ocean every year—twice as much as estimated only four years ago.

These releases of methane and carbon will trap more atmospheric heat, melting more ice, releasing yet more greenhouse gases, and potentially creating a vicious feedback loop. The last time this happened was “The Great Dying” 250 million years ago, when 95% of all the species on earth became extinct.

A study in Nature suggests that a thawing Arctic could release 50 billion tons of methane at any time, the equivalent of a trillion tons of carbon.

Climate scientists who see this doomsday scenario as likely in the near term are a minority. But they outnumber climate scientists who deny human-made climate change.

The second report of the IPCC’s current update was “Impacts, Adaptation, and Vulnerability.” Issued last month, it forecast increasing famine, pestilence, and war.

Climate change has begun to destabilize human society. We see this in the human costs of mega heatwaves, wildfires, a 23-state drought, crop failures, ocean acidification, superstorms, blizzards in unprepared locales, catastrophic typhoons, massive arctic ice melts, and shrinking glaciers.

The world’s food supply is already at considerable risk. Wheat and corn output has sharply declined as a result of droughts in Russia, Brazil, Argentina, and Ukraine. Temperature variations and acidification have already destroyed 40% of the oceans’ phytoplankton, the basis of the oceanic food chain.

Food and water shortages lead to political conflict, mass migrations, and war. This too is already underway.

The Syrian Civil War holds the potential for blowing up he Middle East. Its ultimate roots are not in repression of the Arab-Spring-like protests of March and April 2011. Rather, those protests erupted when the regime was unresponsive to mass impoverishment and starvation resulting from a four-year drought. Climate change over the last 40 years has dried out the Mediterranean area, and Syria was especially hard hit.

The IPCC’s third report, issued last week, is entitled “Mitigation of Climate Change.” It explores 1,200 scenarios for averting disaster and recommends the cheapest and most effective of them. Those options, and the political obstacles to choosing them, are the subject of this two-part series’ second half.