Caldeira Lab

The Great Climate Experiment: How Far Can We Push the Planet?

Ken Caldeira

What would happen if we do not curtail CO2 emissions and burn all of the fossil fuels available? The future would look a lot like how it did 100 million years ago, the age of the dinosaurs, which means high CO2 levels and a very warm planet.

Caldeira, K., 2012b: The Great Climate Experiment. Scientific American, 307, 78–83, doi:10.1038/scientificamerican0912-78.

Ken Caldeira - click to read the video transcript




Business, government or technology forecasts usually look five or 10 years out, 50 years at most. Among climate scientists, there is some talk of century’s end. In reality, carbon dioxide dumped into the atmosphere today will affect Earth hundreds of thousands of years hence. How will greenhouse gases change the far future? No one can say for sure exactly how Earth will respond, but climate scientists—using mathematical models built from knowledge of past climate systems, as well as the complex web of processes that impact climate and the laws of physics and chemistry— can make predictions about what Earth will look like. Already we are witnessing the future envisioned by many of these models take shape. As predicted, there has been more warming over land than over the oceans, more at the poles than near the equator, more in winter than summer and more at night than in the day. Extreme downpours have become more common. In the Arctic, ice and snow cover less area, and methane-rich permafrost soils are beginning to melt. Weather is getting weirder, with storms fueled by the additional heat. What are the ultimate limits of the change that we are causing? The best historic example comes from the 100-million- year-old climate of the Cretaceous period, when moist, hot air enveloped dinosaurs’ leathery skin, crocodilelike creatures swam in the Arctic and teeming plant life flourished in the CO2-rich air. The greenhouse that is forming now will have consequences that last for hundreds of thousands of years or more. But first, it will profoundly affect much of life on the planet—especially us.



Figure: Assuming we continue to burn fossil fuels at will, releasing greenhouse gases such as carbon dioxide unabated into the atmosphere, the planet will be transformed. Already global temperatures have risen by nearly one degree Celsius—more than twice that in the Arctic. Average temperatures may rise by more than five degrees C, enough to melt the vast quantities of water stored as ice in the glaciers of Greenland and Antarctica. Enough water could be released to raise sea levels by 70 meters. Atmospheric concentrations of carbon dioxide will reach levels last seen during the Cretaceous period, when dinosaurs roamed Earth, North America was cut in two by an enormous inland sea and crocodilelike creatures inhabited the Arctic. Figure credited to Scientific American.