Surging levels of carbon dioxide sent greenhouse gases in the atmosphere to a new record in 2013, while oceans, which absorb the emissions, have become more acidic than ever, the UN said on Tuesday.
"We know without any doubt that our climate is changing and our weather is becoming more extreme due to human activities such as the burning of fossil fuels," said Michel Jarraud, the head of the World Meteorological Organization (WMO) that released a report on the issue on Tuesday.
"We must reverse this trend by cutting emissions of CO2 and other greenhouse gases across the board," Jarraud said in a statement.
"We are running out of time," he warned.
Concentrations of carbon dioxide (CO2), methane and nitrous oxide all broke fresh records in 2013, said the report.
Global concentrations of CO2, the main culprit in global warming, soared to 396 parts per million last year, or 142 percent of pre-industrial levels—defined as before 1750.
That marked a hike of 2.9 parts per million between 2012 and 2013 alone—the largest annual increase in 30 years, according to the Greenhouse Gas Bulletin.
The report also showed that so-called radiative forcing, or the warming effect on our climate attributed to greenhouse gases like CO2, increased 34 percent from 1990 to 2013.
A quarter of emissions are absorbed by the oceans, while another quarter are sucked into the biosphere, naturally limiting rates of warming gases in the atmosphere.
But CO2 remains in the atmosphere for hundreds of years and in the oceans for even longer.
The gases stored in the oceans also have "far-reaching impacts," WMO warned, since more CO2 in the water leads to increased acidity, altering the ocean ecosystem.
Every day, the world's oceans absorb some four kilos (8.8 pounds) of CO2 per person each day, WMO said, calling current ocean acidification levels "unprecedented at least over the last 300 million years."
And things will only get worse, Jarraud said.
"Past, present and future CO2 emissions will have a cumulative impact on both global warming and ocean acidification," he said, adding that "the laws of physics are non-negotiable."
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