On the 40th anniversary of Earth Day, the planet is sending us a smoke signal.
A plume of ash from one volcano in Iceland has disrupted travel, commerce and culture across Europe and the globe. Eyjafjallajokull's airborne debris even grounded Air Force One from a planned trip to Poland. Airline losses are estimated at $200 million a day, with further damages spreading throughout the global economy.
In an era of airplanes, cellphones and supercomputers, Eyjafjallajokull is a call for humility. At the same time, a second, invisible eruption has been taking place all around the world. On Eyjafjallajokull's second day, NASA's MODIS-Terra satellite sensor measured a peak of about 80 thousand tons of ash in the atmosphere. By comparison, the invisible eruption sends roughly 80 million tons into the air every day -- not of volcanic ash, but of carbon dioxide, coming out of countless tailpipes and smokestacks. So it seems natural to ask: How much of a disruption could climate change cause?
Some analysts are not very concerned. Compared to an exploding volcano, the pace of warming seems slow. This perception makes it easy to argue that we can absorb or adapt to climate impacts without world-shaking costs -- and that sharp controls on carbon emissions would be more expensive. For example, statistician and climate provocateur Bjorn Lomborg cites research estimating yearly damages that don't even reach 1 percent of global GDP by 2100.
Human inventiveness has conquered smallpox, space travel, and countless other great challenges. It's easy to wonder what damage 5 or even 15 degrees of global warming could do to us today.
To get at an answer, it helps to know that agriculture and human civilization have developed under a very steady climate. According to scientists' best reconstructions of ancient global temperature, the last 10,000 years or so have been abnormally serene. Think of the more typical pattern from before that time as the ups and downs of the Himalayas. By contrast, civilization has simply coasted through the rolling hills of Tuscany.
The long-term record of carbon dioxide in the atmosphere tracks the temperature record well. Scientists believe that higher carbon levels have historically increased temperatures. In the other direction, higher temperatures have also increased carbon levels. This kind of mutual escalation may account for much of the climate instability that prevailed before civilization's dawn. It would have amplified small shifts in Earth's orbit that alone should have had only small climate effects.
Today, human activity is pouring carbon into the atmosphere at a rate that dwarfs any change in the last 800,000 years. The best evidence suggests we are coiling the spring for a far faster and greater sustained change in climate than humans have ever seen. We are inviting the planet to humble us.
Economic forecasts that estimate low costs for adapting to global warming generally neglect the possibility of strong shocks. In light of the havoc wrought by one volcano in a nearly forgotten land, it is difficult to imagine what accelerating global climate change could unleash. Increased heat waves, droughts, storms, extinctions and sea level rise are only some of the familiar consequences underway. But we are really just beginning to appreciate the countless possible ripple effects, whose complexity ought to be another source of humility.
One of the potential outcomes happens to be that melting glaciers on Iceland will reduce the weight compressing underground magma chambers -- and could thus lead to increased volcanic activity.
How many smoke signals will we need before we get the message?
Ben Strauss is a scientist at Climate Central.
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