"Pretty simple, folks: It’s everyone’s responsibility, because it’s the net amount of carbon that
matters, not each country’s share," Kerry said Thursday.

He warned that neglecting to forge an effective plan to fight climate change would be judged a
"massive, collective moral failure of historical consequences."

"If we don’t lead, future generations will not forgive us," Kerry said. "They will want to
know how we together could possibly have been so blind, so ideological, so dysfunctional and, frankly,
so stubborn" by failing to act on overwhelming scientific evidence.

How to divide the emissions cuts that many scientists say are needed to avoid dangerous levels of warming
is a major sticking point in the negotiations toward the global climate pact that governments aim to
adopt in Paris.

Optimism injected into the negotiations last month by a joint U.S.-China announcement on their planned
emissions targets faded in Lima as rich and poor countries argued over the content of the formal pledges
that countries are supposed to make early next year.

Rich countries insist the pledges should focus on efforts to control emissions and are resisting demands
to include promises of financing to help poor countries tackle climate change.

Top carbon polluter China and other major developing countries oppose plans for a review process so the
pledges can be compared against each other before Paris.

Brazil’s top negotiator, Antonio Marcondes, called the review an "unnecessary effort" that
would detract from the main goal of reaching an agreement next year.

Some delegates expressed surprise that China, despite its joint announcement with the U.S., continued to
insist on clear dividing lines between the climate action expected from developed and developing
nations.

"I thought that they would not be as stern as they used to be in the past," said Tony de Brum,
the foreign minister of the Marshall Islands, which is among the small island states that fear they will
be submerged by rising seas caused by global warming.

Liu Zhemin, the deputy head of the Chinese delegation, stressed the principle in the 1992 U.N. climate
convention that rich countries have a greater responsibility to fight climate change. He called China’s
announcement last month that it its emissions would peak by 2030 "a very ambitious target"
that would require tremendous action.

Scientific reports say climate impacts are already happening and include rising sea levels, intensifying
heat waves and shifts in weather patterns causing floods in some areas and droughts in others.

According to the U.N.’s scientific panel on climate change, the world can pump out no more than about 1
trillion tons of carbon to have a likely chance of avoiding dangerous levels of warming. It has already
spent about half of that carbon budget as emissions continue to rise, driven by growth in China and
other emerging economies.

China, the U.S. and the European Union, which are the three biggest emitters, have announced their
emissions targets, but no other country has. Governments are supposed to submit their pledges by the end
of March, though many have said they need more time.

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Associated Press writers Matthew Lee and Frank Bajak contributed to this report.