IStock Photo 3967199 © Chris Crafter

When politicians and lobbyists argue about climate change, some frame it as a yes/no issue: is it happening or not? But few mainstream scientists question whether our planet is warming—the issue is how much and how fast? The more temperatures rise, the more changes we can expect, including stronger hurricanes and high coastal flooding during storms.

Many experts have assigned odds to different ranges of global warming, but MIT’s Joint Program on the Science and Policy of Global Change goes a step further and maps the risks on two roulette wheels. The “no-policy” wheel shows estimates (based on detailed scientific modeling) of how high Earth’s average surface temperature will rise by the year 2100 if nations don’t reduce greenhouse gas (GHG) emissions. The most likely outcome, with odds of one in 2.6, is that temperatures will rise eight to ten degrees Fahrenheit—an increase that would make summer in Boston feel more like Tampa. The odds of a more modest five to eight degree rise are one in 4. More worrisome, the odds of a temperature increase smaller than five degrees are less than one in 100.

The “policy” roulette wheel also assumes that temperatures will rise, but not as sharply, because nations take steps to cap their greenhouse emissions. That brings the most likely increase down to four to five degrees Fahrenheit (one in 2.38 odds), making a Boston summer feel more like Philadelphia. The odds of limiting temperature increases to two to four degrees Fahrenheit are almost as strong (one in 2.63). Many parts of the world would still feel serious effects, from increased flooding in the tropics to melting permafrost in Alaska, but they would be less severe than the no-policy case.

Both wheels tell us that we can expect some warming. And they’re spinning right now as the world’s biggest emitters argue over who should act first. What’s a concerned global citizen to do?

When people face risks with potentially serious consequences in daily life, they often buy insurance. The odds that a US homeowner has home insurance are 1 in 1.05 (95%), and the odds that a single family home in a special flood hazard area has flood insurance are 1 in 2.03 (This kind of special coverage can be very expensive, so some people decide that the risk doesn’t justify paying high premiums).

If we’re facing some degree of climate change and the effects could be disastrous, it might seem that national insurance—in this case, policies to reduce greenhouse gas emissions—would be a prudent investment. The problem is that individuals can choose how much personal insurance to buy based on their own tolerance for risk, but national climate policies make everyone pay the same premium. After years of debate, there’s still little agreement in the US on what costs are justified to slow climate change, especially when Americans are worried about economic growth and job losses.

But here’s a further twist: as climate change worsens, we all incur growing risk to our homes, property, and health. Especially if nations don’t agree on reducing GHG emissions, we may all end up paying more for individual insurance against weather risks and natural disasters instead. Whether you’re a gambler or not, you can’t get out of the climate roulette game.