The Implications of Runaway Warming Even two degrees of warming could set in motion changes that could wreak havoc on ecosystems and world civilization

While world leaders have talked for years about reining in carbon pollution so as not to push the climate beyond 2°C (3.6°F) of warming, emissions are headed in the other direction. According to a report late last year by the International Energy Organization (IEO), the world is currently on track for a 6°C (10.8°F) temperature increase.

runaway warming, credit: Ian Burt, FlickrCC

By many accounts, a mere two-degree temperature increase may already be beyond the world’s grasp, yet the latest climate science suggests that even two degrees of warming may set in motion changes that could wreak havoc on ecosystems and world civilization.

“Concentrations of greenhouse gases in the atmosphere…are very rapidly approaching levels consistent with a 2-2.4° [Celsius] rise in average global temperatures which scientists believe could trigger far reaching and irreversible changes in our Earth, biosphere and oceans,” said Michel Jarraud, secretary-general of the World Meteorological Organization, in a statement.

An analysis published last year by British scientists Kevin Anderson and Alice Bows came to a more alarming conclusion, stating: “There is now little to no chance of maintaining the global mean surface temperature at or below 2°C [3.6° F]. Moreover, the impacts associated with 2°C have been revised upwards, sufficiently so that 2°C now more appropriately represents the threshold between ‘dangerous’ and ‘extremely dangerous’ climate change.”

What extremely dangerous changes? Scientists and meteorologists mention things like feedback loops that could destabilize ecosystems and send temperature hikes into even higher gear. Humanitarians focus on how rising sea levels will force many of the 634 million living along the worlds’ coastlines to abandon their homes, while water shortages and extreme heat and storms take a heavy toll on global agriculture, triggering widespread famine

With a temperature increase above 4°C [7.2°F], crop yields worldwide could fall by as much as 40%, not far from what happened during the 2003 European heat wave. That heat wave, which some scientists think was made worse by global warming, reduced agricultural output by as much as 30% in some countries.

Water supplies will also be tapped out. A 2010 study published by the Natural Resources Defense Council found that more than a third of all counties in the lower 48 states “will face higher risks of water shortages by mid-century as the result of global warming.“ Without climate change, Nebraska, for instance, wouldn’t have a single county in an “extreme” water sustainability crisis, while nearly three-quarters of all counties are looking at “extreme” (41) or “high” (27) water sustainability problems by 2050 when climate change is taken into account, the study found.

And the cost of corrective action is growing the longer we wait. Last November, the IEO concluded that for every $1 of investment in cleaner technology that we fail to spend on developing clean energy in the next eight years, we’ll need to spend an additional $4.30 after 2020.