How should we respond? First, we must recognize that uncertainty and inertia are inescapable features of the climate system. For instance, we know that warming will melt Arctic permafrost, which, when it rots and releases carbon, causes more warming  but how bad will this cycle be? How much of the extra carbon will be absorbed by plants that grow faster in a carbon-rich atmosphere? Inertia refers to the long lags in the climate’s response to human carbon emissions.

Systems with lots of uncertainty and inertia are notoriously hard to control: we can’t effectively predict their future behavior, and we can’t quickly correct behavior we don’t like. By the time we find out that the climate dice have rolled against us, inertia could make conventional responses like carbon taxes and wind power inadequate. Planning our response around what we currently think is the most likely outcome is therefore reckless. We must hope for the best while laying plans to navigate the worst.

Navigating the worst could involve what scientists call geo-engineering  the intentional modification of the earth’s climate. Unfortunately, although specialist circles and blogs are alive with heated conversations about geo-engineering, the idea is so taboo that governments have provided virtually no research money. Most of these conversations focus on the idea of injecting sulfate particles into the stratosphere to screen out the sun’s radiation, as happens when volcanoes erupt. Also, most of the limited scientific research on geo-engineering has aimed to show why sulfate injections won’t work  like why they might damage the ozone layer or produce too much cooling and drying in places where we don’t want these changes.

Yes, it’s vital to have this “red team” of skeptics questioning geo-engineering. But we need more emphasis on a “blue team” to figure out what geo-engineering approaches might work, because we might need to move fast. Instead of replicating volcanoes, we might use synthetic particles made from metals or ceramics designed to scatter sunlight selectively or that exploit the physics that governs the motion of small particles in the upper atmosphere so that cooling is focused at the poles where it’s needed most.

Of course, flooding the atmosphere with man-made particles poses real risks. So to reduce the uncertainty surrounding geo-engineering, research should include real-world tests of various technologies that poke the climate system just a little. At first, tests might use existing research aircraft like NASA’s ER-2, a heavy version of the U-2, to release small payloads of particles and then measure the effects on solar radiation and the ozone layer. If these early tests showed the risks were low, enough material could then be released to have a detectable climate impact, while still keeping the amount substantially less than that needed to offset all human-driven global warming.