Concentrations of CO2, methane and nitrous oxide all broke records in 2013, report says

Surging levels of carbon dioxide sent greenhouse gases in the atmosphere to a 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, which 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. "We are running out of time."

Concentrations of carbon dioxide, methane and nitrous oxide all broke records in 2013, the report said.

The volume of carbon dioxide, or CO2, the primary greenhouse gas emitted by human activities, was 396.0 parts per million in 2013, 2.9 ppm higher than in 2012, the largest year-to-year increase since 1984, when reliable global records began.

Historic climate deal

The second-most important greenhouse gas, methane, continued to grow at a similar rate to the last five years, reaching a global average of 1824 parts per billion. The other main contributor, nitrous oxide, reached 325.9 ppb, growing at a rate comparable to the average over the past decade.

The report came ahead of a Sept 23 summit called by UN Secretary-General Ban Ki-moon to try to build momentum for change ahead of talks next year aimed at forging a historic climate deal that will take effect in 2020.

The UN is seeking to limit global warming to 2 degrees C over pre-Industrial Revolution levels, but scientists say current emission trends could hike temperatures to more than twice that level by century's end.

"We have the knowledge and we have the tools for action to try to keep temperature increases within 2 degrees Celsius to give our planet a chance and to give our children and grandchildren a future," Jarraud said, insisting that "pleading ignorance can no longer be an excuse for not acting".

Dave Reay, chair in Carbon Management at the University of Edinburgh, reacted with dismay to the report.

"This is the litmus test when it comes to our efforts to reduce emissions, and on this evidence we are failing," he said.

Radiative forcing

Tuesday's report also showed that so-called radiative forcing, or the warming effect on our climate attributed to greenhouse gases like carbon dioxide, 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 about 4 kg 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".

AFP - Reuters

(China Daily 09/10/2014 page11)