earth on fireA WIDELY read cover story on the impact of global warming in this week’s New York magazine starts ominously: “It is, I promise, worse than you think.” It goes on to predict temperatures in New York hotter than present-day Bahrain, unprecedented droughts wherever today’s food is produced, the release of diseases like bubonic plague hitherto trapped under Siberian ice, and permanent economic collapse. In the face of such apocalyptic predictions, can the world take solace from those who argue that it can move, relatively quickly and painlessly, to 100% renewable energy?

At first glance, the answer to that question looks depressingly obvious. Despite falling costs, wind and solar still produce only 5.5% of the world’s electricity. Hydropower is a much more significant source of renewable energy, but its costs are rising, and investment is falling. Looking more broadly at energy demand, including that for domestic heating, transport and industry, the share of wind and solar is a minuscule 1.6% (see chart). It seems impossible to eliminate fossil fuels from the energy mix in the foreseeable future.

But all energy transitions, such as that from coal to hydrocarbons in the 20th century, take many decades. It is the rate of change that guides where investments flow. That makes greens more optimistic. During the past decade, solar photovoltaics (PV) and wind energy have been on a roll as sources of electricity. Although investment dipped slightly last year, the International Energy Agency, a global forecaster, said on July 11th that for the first time the amount of renewable capacity commissioned in 2016 almost matched that for other sources of power generation, such as coal and natural gas. In some countries the two technologies—particularly solar PV in sunny places—are now cheaper than coal and gas. It is no longer uncommon for countries like Denmark and Scotland to have periods when the equivalent of all their power comes from wind.

Continue reading at The Economist