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After years of gloom, the forecast is brightening for the effort to combat destabilizing changes in the global climate. While formidable barriers still impede domestic and international action, other signs point to new alliances and momentum that could generate meaningful gains.

Two white ducks walk along the beach at Aqualand Marina as emissions spew out of a large stack nearby at the coal-fired Morgantown Generating Station on the Potomac River. (Mark Wilson/Getty Images)In panels I moderated last week at the Aspen Ideas Festival, three leading environmentalists—Fred Krupp, president of the Environmental Defense Fund; Mark Tercek, president and CEO of the Nature Conservancy; and Tom Steyer, the billionaire investor and activist who spent $75 million of his money backing (mostly unsuccessful) candidates committed to climate action in the 2014 election—each pointed to breaks in the clouds. "I am much more optimistic than five years ago," said Steyer. Added Tercek: "We can't be glib: The challenges are huge. But "¦ the logjam seems to be breaking."

The trio's shared optimism contravenes the environmental community's widespread fear that world leaders are sleepwalking toward a rise in atmospheric temperatures that would disrupt the global environment. None of the three believes the international community has yet adopted policies that sufficiently constrain that danger. But they all see a pathway toward that point as the next round of international climate negotiations approaches this fall in Paris.

Opportunities are converging from above and below. Though many environmentalists initially questioned President Obama's commitment to the climate cause, Krupp, Tercek, and Steyer now praise him for an agenda that includes a significant first-term increase in fuel-economy standards for cars and light trucks, and for the impending Environmental Protection Agency rule that will require states to draft plans to reduce carbon emissions from their existing power plants.

Krupp argues that Obama's domestic actions have, in turn, dislodged the international stalemate. Last November, Obama reached an agreement with Chinese President Xi Jinping in which the U.S. promised to cut its carbon emissions by about one-fourth through 2025 and China pledged to reach its peak emissions by around 2030. Krupp acknowledges that the U.S. and China, which is the world's biggest carbon emitter, eventually must do more. But even so, Krupp said, the agreement is "the biggest thing that has happened in the last 12 months, because it takes away the excuses of people in both countries that the other country isn't going to move." The agreement pressures other nations to bring their own serious commitments to the Paris talks as well.

New allies are also joining the cause, both at home and internationally. The biggest is Pope Francis, whose encyclical on climate change supplements economic and environmental arguments with a spiritual case for action. In the United States, Krupp notes, the effects of extreme weather are mobilizing unexpected constituencies such as Southwestern ranchers and ski-resort owners.

Yet entrenched obstacles remain. The International Energy Agency recently reported that the national pledges submitted to the climate talks, if implemented, would hold the increase in carbon emissions to just 8 percent while the world economy grows by 88 percent through 2030. While impressive, the agency concluded those reductions wouldn't significantly diminish climate risks without substantial further cuts later on.

At home, most Americans say they believe that human activities have changed the climate. But the partisan divide over limiting carbon emissions remains gaping, partly because the most conservative states typically rely most on fossil fuels: Four-fifths of the states that preferred Mitt Romney over Obama in 2012 emit more carbon per capita than the national average. Five Republican governors are already signaling they won't submit plans to meet the EPA carbon reductions, and more will inevitably sue to block the rules. No top-tier GOP presidential candidate is pledging national action.

In this tenuous moment, the tipping point may be whether business sees the transition to a low-carbon economy as more threat or opportunity. Steyer said the main reason he's optimistic is the dynamic business investment developing around efficiency and clean energy. "It's incredibly exciting "¦ to see what American business can do [with] the bit in its teeth," he said. Tercek and Krupp, whose organizations often partner with business, also see indications of growing boardroom concern. Even so, while six European oil companies recently endorsed carbon emission limits, very few U.S. corporations have publicly supported government action.

Could that change? When I interviewed Steyer in Aspen, David Koch, the conservative energy and chemicals magnate, sat in the front row; afterward, the two billionaires, who spent millions of dollars attacking each other's candidates in 2014 races, talked alone for the first time. Both during the session and after, Steyer asked Koch to indicate publicly whether he views climate change as a legitimate threat. Koch hasn't yet responded to Steyer's request. If he were to say he believes the climate is warming, it would help shift the debate from whether to respond to the change to ­how. That would represent a political earthquake. But even if that tremor never comes, the other economic and political forces converging at home and abroad may still provide a jolt of momentum for the daunting struggle to stabilize the global environment.

This article is from the archive of our partner National Journal.

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