Each week, In Theory takes on a big idea in the news and explores it from a range of perspectives. This week we’re talking about the ethics of global warming. Need a primer? Catch up here.

Daniel Farber teaches environmental law and tort law at the University of California at Berkeley.

Our moral duty to address climate change is based on a simple concept, straightforward enough to qualify as kindergarten fare. We tell our children that they need to be careful not to hurt their playmates. As we get older, we learn that we need to be careful when we engage in other activities too — we shouldn’t drive after drinking, or leave loaded guns around children. The same simple concept can take us a long way in thinking about our policies to address climate change.

Those who emit carbon don’t mean to cause harm, any more than a kid playing backyard baseball means to knock out a neighbor’s window. But it’s not enough to have good intentions. We’re not required to avoid ever doing anything that could possibly harm others — there’s no way to avoid every possibility — but we do have a duty to take reasonable precautions to prevent avoidable damages.

Defining what is reasonable in a particular context can be difficult, but it generally involves consideration of the foreseeable risks and the burden of installing preventative measures. As to climate change, the question is whether we have taken reasonable precautions in light of the available evidence.

There’s room for debate about when the dangers of climate change became clear enough to elicit a response, but the evidence definitely arrived well before the end of the 20th century. By then, scientists agreed that greenhouse gases were causing global warming and that continued warming was likely to become dangerous. In fact, in 1992, the world’s nations — including the United States under President George H.W. Bush — signed a treaty acknowledging the risks and the need for action.

Given that the risk from climate change is high and foreseeable, it seems clear that reasonable precautions are called for (and have been for some time now). Economists who have studied climate change carefully disagree with each other about just how fast we should reduce carbon emissions. Some say we should start out with modest emissions reductions; others call for immediate, stringent limitations. Still, taking into account the costs of reducing emissions and the risk to the planet, they all agree that reductions are necessary.

At the risk of oversimplification, one might boil this down to a simple mandate to phase out emissions from coal as soon as reasonably possible. Coal is the worst fossil fuel in terms of emissions. It’s often touted as a cheap energy source, especially for developing countries, but its price is an illusion once we taken into account the hidden costs. Coal mining remains a dangerous occupation, and mining can cause severe environmental harm.

But more important, emissions from coal cause more than climate change: They are the source of severe health problems. Even in the United States, which has been requiring improved pollution control for coal plants for decades, emissions continue to result in thousands of deaths a year. Our pollution issues are nothing compared with those of Beijing or many other cities in China and India.

Continued reliance on coal for energy is as foolish as drunken driving. We should develop alternatives as soon as possible, even in developing countries. As always, the standard should be what is reasonable — somewhere between shutting down coal plants today and waiting for new technology that could save us.

You might question comparing carbon emissions to ordinary careless behavior. It’s certainly true that identifying who is the injured party in a car accident is easier than defining who is suffering from the additional boost our own actions are giving climate change. But how can we justify carelessly harming others simply because it is difficult to identify who will be hurt?

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