WASHINGTON • The level of carbon dioxide in the atmosphere increased at a record pace last year, United States government scientists reported, raising new concern about one of the top greenhouse gases and global warming.
The measurement came from the National Oceanic and Atmospheric Administration (NOAA) Mauna Loa Observatory in Hawaii as US President Barack Obama and Canadian Prime Minister Justin Trudeau announced joint efforts to curb emissions of planet-warming gases.
The NOAA said the annual growth rate of atmospheric carbon dioxide jumped by 3.05 parts per million last year, "the largest year-to-year increase in 56 years of research".
Last year also marked the fourth consecutive year that CO2 grew more than two parts per million.
As of last month, the average global atmospheric CO2 level was 402.59 parts per million. This is a significant rise over pre-industrial times. Prior to 1800, atmospheric CO2 averaged about 280 ppm.
"Carbon dioxide levels are increasing faster than they have in hundreds of thousands of years," said Dr Pieter Tans, lead scientist of NOAA's Global Greenhouse Gas Reference Network. "It's explosive compared with natural processes."
NOAA said the jump in CO2 is partially due to the weather phenomenon known as El Nino, which warms some parts of the world's oceans and causes unusual precipitation and drought patterns.
The rest of the growth is driven by continued high emissions from fossil fuel consumption, said NOAA.
The last time a similar jump in CO2 was observed was in 1998, also a strong El Nino year.
"The impact of El Nino on CO2 concentrations is a natural and relatively short-lived phenomenon," said a statement by World Meterological Organisation secretary-general Petteri Taalas.
"But the main long-term driver is greenhouse gas emissions from human activities. We have the power and responsibility to cut these," he added.
"This should serve as a wake-up call to governments about the need to sign the Paris Climate Agreement and to take urgent action to make the cuts in CO2 emissions necessary to keep global temperature rises to well below 2 deg C."
President Obama and Mr Trudeau announced on Thursday they were teaming to reduce the release of methane, a chemical contained in natural gas. They promised that their two countries would "play a leadership role internationally in the low carbon global economy over the coming decades".
As part of the announcement during Mr Trudeau's official visit to Washington, US officials said they would immediately begin a new push to regulate methane emissions from existing oil and gas facilities, though finishing that process before the end of Mr Obama's tenure is unlikely.
The Obama administration wants to cut methane emissions from the oil and gas sector by 40 to 45 per cent from 2012 levels by 2025. The Interior Department has proposed a number of regulations on methane leaks, but it has yet to write a regulation governing such leaks from current oil and gas drilling on public land.
Mr Obama and Mr Trudeau also pledged to cooperate in preserving the Arctic, and to move more quickly to carry out agreements made in climate talks in Paris last year.
While Canada and the US have long been close allies, Mr Obama's efforts to confront global warming had been a major point of contention with Mr Trudeau's predecessor Stephen Harper, who sought to aggressively expand Canada's oil industry.
AGENCE FRANCE-PRESSE, NEW YORK TIMES