climate policy

Accounting for scientific uncertainty in a dangerously warming world

Most people at some point develop a “Plan B” – in case their first choice of college doesn’t accept them, or it rains on the day of their planned outdoor party, or the deal for the house they wanted falls apart. The same principle applies for more dire situations, such as a city having plans in hand for an orderly evacuation in case of a large-scale disaster. We hope such an event will never happen, but the mayor had better be prepared in case it does.

In a commentary today in the scientific journal Nature Climate Change, three colleagues and I discuss the need for a “Plan B” for climate change: How will we cope with increasingly severe climate impacts if we are unsuccessful in limiting global warming to a chosen target?

In the 2009 Copenhagen climate accord, countries set a goal of limiting global warming to below 2 °C (3.6 °F) above the average global temperature of pre-industrial times. However, given that the planet has already warmed by 0.8 °C, additional warming is already locked into the system, and global greenhouse gas emissions continue to rise, this “Plan A” has become increasingly difficult and may become impossible to achieve if widespread emissions reductions do not begin within this decade. A maximum warming target is a necessary goal of climate policy, but what if our efforts fall short?

Some voices in the environmental community will feel that asking this question is ceding failure, but I disagree. Instead, it means admitting that we can’t perfectly foresee the future and that we need to be prepared for surprises. This is called risk management and everyone from parents, to mayors, to companies, to the U.S. military uses risk management every day to cope with uncertainty.

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