VATICAN CITY (AP) — John Kerry, President Joe Biden’s climate envoy, met privately with Pope Francis on Saturday, afterward calling the pope a “compelling moral authority on the subject of the climate crisis” who has been “ahead of the curve.”

The former U.S. Secretary of State told Vatican News that the pope's embrace of climate issues “hopefully can push people to greater ambition to get the job done.”

Kerry is visiting European capitals to strengthen cooperation on climate change ahead of the next round of U.N. climate talks in Glasgow this November.

Kerry said United States, the second-largest emitter of greenhouse gases after China, must take a lead in cutting emissions and be joined by other big emitting countries.

“Everybody shares an obligation here. No one country can get this job done. If the United States was at zero emissions tomorrow, we’d still have crisis,” Kerry said.

The United States, which is responsible for 11% of the world's greenhouse gas emissions, has set a target under Biden of reducing emissions over the next decade by 50% to 52%, Kerry said.

Another 20 developed countries are responsible for 73.75% of emissions, he added.

“We need other big emitting countries to step up and also offer some reductions. You can’t just keep going along with a coal-fired power plant or with more coal coming online and really be the part of the solution that we need,’’ Kerry said.

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