The Paris climate deal is, potentially, an important first step toward addressing climate change. But some of the headlines have been wildly overstated, saying the treaty marks the "end of the fossil fuel era."

That's awfully premature. Oil, gas, and coal still make up about 86 percent of the world's energy supply — a fraction that has barely budged since 1997. Until that drops sharply, we can't really declare the end of the fossil fuel era:

Yes, there are some genuinely hopeful signs that this is changing. Solar and wind power consumption is growing at 15.9 percent per year, whereas coal, oil, and gas are growing at less than 1.7 percent per year. But renewables are still rising from a tiny base, and in many cases can't yet offer the reliability or versatility of fossil fuels. By and large, oil, gas, and coal continue to rule our world.

Robert Wilson puts it vividly: "Fossil fuels continue to dominate new energy infrastructure. Maersk is not unveiling solar powered container ships. Boeing and Airbus appear content with the age of kerosene. Steel makers are sticking with coal. 20 million new cars are added to China’s roads each year. ... India plans to double its coal production by 2020. Green Germany just opened a new coal power plant last month." And on and on.

It will take massively ambitious measures to halt these trends and shift toward cleaner energy. To prevent serious global warming, as the University of Colorado's Roger Pielke Jr. likes to point out, carbon-free sources will have to rise from 14 percent of the energy supply today to more than 90 percent by the second half of the century.

This @rogerpielkejr chart is a good way to visualize the scale of the climate challenge. A *lot* more work to do: pic.twitter.com/HY96FyEPgJ — brad plumer (@bradplumer) December 12, 2015

That means (roughly) deploying 1 gigawatt of carbon-free power every single day for the next century — the equivalent of opening a large nuclear power plant around the world every day, or raising 1,500 wind turbines every day. It will mean shifting our cars and trucks to clean electricity, overcoming the intermittency problems with renewables, radically increasing energy efficiency, finding new ways to fuel our ships and airplanes (hydrogen? biofuels?) and steel and cement production.

This isn't impossible, at least not in theory. The detailed reports from the Deep Decarbonization Pathways Project offer a vivid illustration of how we might make that shift to clean energy. But it is hard. It will require much more than a single climate treaty that corrals fairly weak and largely voluntary national efforts. And that's the real work that lies ahead. Declaring victory after Paris is premature.

Read more: The world just agreed to a major climate deal in Paris. Now comes the hard part.