Global emissions of greenhouse gases jumped 2.3 percent in 2013 to record levels, scientists reported Sunday, in the latest indication that the world remains far off track in its efforts to control global warming.

The emissions growth last year was a bit slower than the average growth rate of 2.5 percent over the past decade, and much of the dip was caused by an economic slowdown in China, which is the world’s single largest source of emissions. It may take an additional year or two to know if China has turned a corner toward slower emissions growth, or if the runaway pace of recent years will resume.

In the United States, emissions rose 2.9 percent, after declining in recent years.

The new numbers, reported by a tracking initiative called the Global Carbon Project and published in the journal Nature Geoscience, came on the eve of a United Nations summit meeting meant to harness fresh political ambition in tackling climate change. Scientists said the figures showed that vastly greater efforts would be needed to get long-term global warming within tolerable limits.

“You can no longer have some countries go first and others come in later, because there is no more time,” said Glen P. Peters, a scientist at the Center for International Climate and Environmental Research in Oslo, who helped compile the new numbers. “It needs to be all hands on deck now.”

Yet expectations for the summit meeting on Tuesday are low, with no sign of any political breakthrough that would lead to more ambitious efforts. Scientists say emissions must peak within the next few years, and then begin to decline, if the world is to have any hope of keeping global warming to an upper limit that countries agreed on five years ago. So far, no plans are in place that would come close to achieving that.

Emissions have been falling gradually in recent years in most of the developed