The same week that President Obama at long last rejected the Keystone pipeline, officials in New York State started investigating whether Exxon Mobil had for decades lied to the public—and denied its own research—about the risks and causes of climate change. One can sense momentum shifting in the politics of climate change.

That momentum could get another boost in early December when world leaders gather outside Paris for a major United Nations conference—pared down after the devastating terrorist attacks of November 13—on climate change. The primary aim is to finalize a pact to reduce greenhouse gas emissions so as to limit global temperature rise to 2° C above preindustrial levels.

Many nations are still sketchy about their commitments and the extent to which their pledges are binding. Scientists disagree about what difference one conference can make. Business leaders argue that economic incentives are the best way forward.

But several things are new since the Kyoto Protocol of 1999. For one thing, Exxon Mobil now acknowledges that emissions contribute to climate change. The United States has also drafted an ambitious preconference plan, saying it will cut carbon emissions by 26 to 28 percent by 2025. The European Union and Canada and 150 other nations have put similar plans on the table. While not setting a target for reducing emissions, India has put together a plan to invest in renewable sources of energy. China and the United States—two nations that account for over one-third of global greenhouse gas emissions—announced in November an aggressive joint agreement on limiting emissions. Meanwhile, public and private investment in renewable energy sources such as wind and solar have risen exponentially as their costs have dropped.

To keep momentum moving, the United States needs not only to follow through on its own plans, but also to help developing nations pursue their goals. Obama has pledged $3 billion to developing nations working toward nonfossil fuel energy economies—money that is currently being held captive in Congress. Public pressure can also be brought to bear on the 90 companies that researchers have identified as responsible for two-thirds of all carbon emissions. Clear “fingerprinting” of emissions is one way to make sure pressure stays on these companies. Congress should also renew tax incentives for solar power, set to expire in 2017.

Even if the new global standards are met, the world will not escape the effects of climate change. Andrew Jones, the codirector of Climate Interactive, an MIT-affiliated climate policy group, believes that even an optimistic reading of the trends points toward “a world that we would not be able to adapt to.”

But it’s possible the Paris conference will be a turning point, the moment the world leaders agree, in the words of Jennifer Morgan at the World Resources Institute, that “there’s just one direction” to go with emissions—down.