Weather on the Juice?

A common analogy to explain the link between climate change and extreme weather is gambling with “loaded dice.” For people who aren’t the gambling type but love America’s pastime, perhaps Barry Bonds’ homerun statistics would be more enlightening, or at least more entertaining. A new video from the National Center for Atmospheric Research draws an analogy between a batter on steroids and the “doping” of the atmosphere with manmade CO2.

The climate system works in a similar way, where the increase in the frequency of extreme weather events over years leads to strong evidence of a linkage between global warming and extreme weather, but any individual event might have occurred without global warming. It is precisely the accumulation of many events that make the overall enhancement detectable.In baseball, any single home run is not “caused” by steroids, just as a single weather event is not “caused” by climate change. However, as home runs accumulate over the course of a season or years, the increased success in slugging is noticeable. Still, Barry Bonds can hit homeruns without steroids, so it remains impossible to say which homeruns he would not have hit without the juice.

Looking back at a player’s history, it might be possible to determine approximately at what point in his career he began taking steroids by examining when the increase in power started, although it’s possible he just got better with experience. With climate change, however, this detective work is unnecessary because we have an excellent data record of exactly how much dope (i.e. CO2) has been injected into the atmosphere, a record of the frequency of various types of extreme events, and a scientific explanation as to why more CO2 increases the risk of extreme weather. This theory and observation provide two independent lines of evidence that enables us to assess the risk of extreme weather events from global warming. Additional evidence comes from modeling, which shows an enhanced risk of certain types of extreme weather when CO2 levels are elevated in a model simulation. Unlike the baseball metaphor, modeling also allows us to project risk into the future. Not every type of extreme weather event is connected to global warming by all three lines of evidence—tornadoes, for example—but for heavy precipitation (both rain and snow), extreme heat, drought, and wildfire, the link is strong.

For both baseball and climate change, making good decisions requires risk management. In baseball, a manager will use information on the probability that a batter hits a home run—a juiced up Barry Bonds presents a bigger threat than almost any other batter—combined with the number of men on base, the score, the number of outs and innings remaining to make a decision that maximizes the chances of winning the game. A home run in a tie game with two outs in the bottom of the ninth is fatal and the manager might choose to intentionally walk the batter instead. By comparison, the risk is small if the defensive team has a five run lead and the manager would prefer to risk a home run than have a man on base. The baseball manager is calculating the likelihood of occurrence, combined with the team’s vulnerability to a home run to make the best decision possible.

As a society, we must now become climate risk managers and make similar calculations. We must understand how the risk of extreme weather is changing and combine this information with the vulnerability of our systems (e.g., a town or a company) in order to make decisions that will best protect our assets. This is the essence of risk management. Successfully managing the risks posed by climate change will require both measures to reduce the amount of steroids (greenhouse gases) in the atmosphere as well as astute managers who are able to contain the impact when Mother Nature hits one out of the park.