There are essentially only three long-run solutions to the climate challenge. The first is to price carbon emissions to reflect the damages from climate change. In practice, this means pricing carbon in as many parts of the world as possible — and ideally, globally — so that there is a level playing field for all energy sources. There has been important progress in this area, including in the European Union, individual American states and regions (for example, California and the Northeast’s Regional Greenhouse Gas Initiative), and parts of China.

And there are several ways to introduce carbon pricing, as a New York Times Op-Ed by David Hayes and James Stock underscored. But we are a long way from a global price on carbon, and the prices in existing carbon markets are lower than the projected damages from increased carbon emissions.

The second way to disrupt the energy market is to have low-carbon energy sources like nuclear, wind and solar become cheaper than their fossil fuel competition. Although there has been much progress in reducing the costs of wind and solar recently, they generally remain more expensive than fossil fuels. Further, the fracking revolution makes it clear that there will be continued technical advances that reduce the costs of recovering fossil fuels.

Indeed, it is well known that there are ample supplies of coal deeper beneath the Earth’s surface that do not yet qualify as resources, and there is increasing evidence that energy from methane hydrates may become relevant commercially. In other words, it seems unlikely that today’s low carbon energy sources will play a major role in the solution without significant public investment in research, development and test deployments of new technologies.

The third approach is to continue using those fuels, but capture and store the carbon before it is released or pull it out of the atmosphere after its release. Neither approach has yet been proved to work at scale, and costs remain high. Even if costs come down, it will very likely remain more expensive than using fossil fuels without capture and storage, so a carbon price would be necessary for it to be applied broadly. A related idea is to reflect sunlight away from the earth so temperatures do not rise as much. This approach does not reduce the buildup of carbon dioxide in the atmosphere, and there is agreement that further research is necessary.

If we use all of the fossil fuels in the ground, the planet will warm in a way that is difficult to imagine. Unless the economics of energy markets change, we are poised to use them.