It is fairly well understood by now that releasing carbon dioxide and other greenhouse gases into the atmosphere imposes an economic cost, in the form of climate change impacts. In most cases, however, those responsible for carbon emissions are not required to pay that cost. Instead, it’s borne mainly by the world’s poor and low-lying countries, and of course by future generations, as many of the worst impacts of climate change will emerge years after the emissions that drive them. People sometimes refer to the unpaid cost of carbon pollution as a subsidy, or an “implicit subsidy,” to polluting businesses. The IMF recently issued a report saying that total worldwide subsidies to energy, mainly fossil fuel energy, amounted to $5.2 trillion a year. The reason that number is so high is that the IMF includes implicit subsidies — the social costs imposed by businesses (including climate damages) that they don’t have to pay for.