The unprecedented wildfires on the West Coast should cause a sea change in the way Americans think about climate-change risks. Instead of assuming we know all the problems a warming planet will cause, we should assume there will be unexpected and calamitous disruptions. This makes the challenge of slowing down climate change even more urgent.

It’s hard to overstate how devastating the wildfires in California and Oregon are. In California, the biggest fire season on record before this year was 2018, with almost 2 million acres burned. Only halfway through the peak wildfire season, 2020 is already at almost 3.5 million acres. Oregon is similarly affected, with mass evacuations and apocalyptic air quality in many cities.

Climate change is not the only reason for the fires. Years of inadequate forest management have raised the risk of blazes. But experts agree climate change has caused protracted droughts that have dried out vegetation, meaning much more fuel is now available for fires. So the amount of improvement in forest management practices necessary to reduce fire risk is much greater than it would have been if humans hadn’t been warming up the planet.

This is the worst year for wildfires on record, but if current trends continue, there will be worse years to come. Though the West Coast may gain a brief respite due to the sheer amount of fuel burned this year, plants will grow back, and climate change will dry out more acres. Mass evacuations, once extremely rare, will become routine. Cities from Seattle to San Diego will be blanketed with stinging, toxic smoke for weeks or even months out of every year. Sunshine and mild climates used to be the reason everyone wanted to move to California. In the new normal, many will prefer to stay or move away.

That could hammer the U.S. economy. The three Pacific Coast states together produce about a fifth of gross domestic product – most of that in the major metropolitan areas. If the technology and entertainment industries must relocate to areas not choked by smoke, then the disruption to the nation’s economic geography will be severe. Swathes of fertile farmland and wine country could become uninhabitable. Huge tracts of property could lose value, destroying many fortunes.

It’s important to realize this is not the climate risk people expected. The most commonly cited effects of global warming are hotter weather and sea level rise. These were expected to advance in stately fashion over the course of decades. To some, this seemed to give us breathing room – time to plan, to mitigate warming, and to learn how to adapt. Others, though they’d probably be loath to admit it, used climate change’s supposed long horizon as a reason not to worry, thinking they’d be dead before the real problems arrived.

And others dismissed the threat entirely. Respected climate economists Olivier DeschĂȘnes and Michael Greenstone wrote a paper in 2007 that assumed the harm from climate change could be calculated by observing how mortality rates tend to vary with heat. This is an absurd assumption, as it neglects both economic disruptions and new dangers that don’t currently exist. Relying on this faulty idea, and assuming people would be able to mitigate the harms they did include in their model, the economists claimed climate change wasn’t a big threat.

It should now be clear that climate change poses harms that go far beyond simple heat, or even rising sea levels. The West Coast wildfires illustrate how the planet is a delicate web of weather, ecology, economics and infrastructure; any disruption to that web is likely to have large unforeseen reverberations. What really gets you are, in the immortal words of former Defense Secretary Donald Rumsfeld, the unknown unknowns.

At least one economist did understand this principle. Martin Weitzman, who died last year, recognized the true cost of climate change lay not in the likely outcomes, but in the tails of the distribution. This means most of the economic cost-benefit analyses people use to urge moderation on climate policy are utterly unreliable.

Instead of being moderate in our climate strategy, the U.S. and other countries need to be bold. There is no more time to waste; terrible things are happening because of climate change, and only decisive action can prevent even more terrible surprises.

This means the U.S. must reduce its own greenhouse emissions, by rapidly adopting green energy sources, switching to electric vehicles and decarbonizing buildings and factories. But as the vast majority of emissions are produced outside the U.S., we also need to both help and push other countries to decarbonize at the same time – by disseminating green technologies cheaply, by subsidizing green industrialization in developing nations such as India, and by taxing carbon-intensive products from countries such as China.

The alternative to that bold program is simply to sit, endure the searing smoke, and wait for the next horrible surprise. It’s not a good alternative.

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