If you knew that our world was likely to destruct, you would do anything to prevent that from happening. But what if there is only a remote chance it will destruct? How much would you do to try to block that possibility?
It depends on how small that chance is, weighed against the cost of what you have to do, you may say. Enter Martin Weitzman, professor of economics, who is grappling with exactly that question. It is not entirely a theoretical one: the worst case scenarios of global warming involve environmental triggers that could rapidly heat the earth by 10 degrees Fahrenheit and bring a massive sea level rise such as the planet has not seen in millions of years.
Scientists and economists traditionally consider those catastrophic, worse-case scenarios as being of such tiny probability that they discount the prospect entirely. In the traditional bell curve of risk, the chances are so far out on the extreme thin tail of probability that they are treated as zero.
Weitzman argues that reasoning is flawed. It is based on an assumption the reaction of the environment to global warming will be constant. In fact, geological history shows the climate has changed swiftly at unexpected tipping points. Weitzman says the more accurate bell curve of risk has a “fat tail” showing a higher chance that horrendous events will occur.
“There is a more serious probability than comes out of standard analysis. But how much? I can’t tell you,” Weitzman says.
That is his frustration, Weitzman acknowledges, and it is of little help to policy-makers. He sees the flaws in the traditional model, but concludes that there is no way to scientifically predict the real probability of catastrophe. In the end, we are all left with little more guidance than to listen to our gut feelings, he says.
“Scientists are in a quandary. These low-probability/high-impact events are so insufficiently understood, the scientists stay away from these kinds of things. But their intuition tells them that this is really quite dangerous. They can’t exclude them.”
A prudent response is to take some steps to at least minimize the potential risk. Society does this in deciding how much to spend at airport security against terrorism, on precautions against biochemical threats, or in constructing antiballistic missile systems, for example.
Weitzman says society ought to do the same for extreme climate change risks, by taking such measures as promoting nuclear energy, where risks are more understood, or by considering geo-engineering schemes that could be employed in emergencies.
“To some extent we have been deluding ourselves by relying on the risk models that we have,” he says. “They look a lot more neat and crisp than the situation really is. They don’t telegraph the events that are really off the charts.”