Fresh Start for a Critical Relationship Between the U.S. and China There was never any guarantee that President Obama and President Xi Jinping of China would end their informal talks over the weekend with a deeper and more productive relationship. On too many issues, their national interests diverge. Even so, their meeting seems to have laid a reasonable basis for cooperation and for managing the inevitable competition between rising and established powers. There were two concrete results, including an agreement to discuss ways to curb the emission of hydrofluorocarbons, known as HFCs, an important step in addressing global warming. Under the 1987 Montreal Protocol, the current generation of HFCs - the heat-trapping chemicals that are used in air-conditioning and refrigeration - replaced older refrigerants that were depleting the ozone. But while they succeeded in preserving the ozone, they turned out to be powerful greenhouses gases that are accelerating climate change and now themselves must be replaced. Previously, China objected to tackling the HFCs, which it produces in large quantities. Now, Mr. Xi and Mr. Obama said they would work within the protocol on a global phasedown that could significantly reduce the gases by 2050. This would eliminate a powerful greenhouse gas, and it might also provide momentum toward a broader global agreement aimed at the reduction of other greenhouse gases like carbon dioxide. The two sides also made important progress on North Korea, whose leader, Kim Jong-un, in recent months has raised regional tensions with belligerent rhetoric and nuclear and missile tests. Under pressure from China, its chief ally, North Korea agreed to hold high-level talks with South Korea later this week, the first in six years. But that's unlikely to produce results unless Mr. Xi keeps the pressure on the North and shows sustained interest in curbing its nuclear program. There was no sign that any headway was made on the issue that Washington considers most pressing: cyberattacks by hackers linked to the Chinese military and the stealing of American military and economic secrets. While unfortunate, that's not a surprise since American officials predicted that it would take time to lay out their evidence and convince the Chinese government that such activities could seriously threaten relations between the United States and China. They will have another chance to engage on the subject when they convene a senior-level strategic dialogue next month. Nor was there any apparent progress on finding ways to ease China's increasingly assertive territorial claims in the South China and East China Seas, which are stirring dangerous tensions with Japan and South Korea. On human rights, the signals were disquieting. While the Chinese government granted passports to relatives of Chen Guangcheng, a blind lawyer who sought asylum in the United States last year, a Chinese court on Sunday sentenced a brother-in-law of Liu Xiaobo, the persecuted Nobel Peace Prize winner, to 11 years in prison on trumped-up charges of fraud. But the presidential summit meeting was more about each leader getting a feel for the other and figuring out how they could work constructively with each other. On that, they seemed to make some headway. If they can resist political forces that are stoking distrust between the two countries and maintain a dialogue, maybe they can achieve the "new model" of relations they pledged to build. That would be a significant move for both nations.