Atmospheric greenhouse gas levels hit record, report says

Atmospheric greenhouse gas levels hit record, report saysGlobal concentrations of carbon dioxide in Earth’s atmosphere surpassed 400 parts per million for a monthly average this past spring, breaching a symbolic barrier set by climate scientists and policy makers, according to a report released Monday.

Concentrations of other greenhouse gases produced from human activities, such as methane and nitrous oxide, also reached records in 2014, the World Meteorological Organization announced in its annual Greenhouse Gas Bulletin. The report is one of several measurements made by different climate agencies to address the state of greenhouse gases in advance of the Paris Climate Summit.

“This evidence shows us that the concentrations are increasing, and they are increasing with increasing rates,” said Oksana Tarasova, chief of the W.M.O.’s Atmospheric Environment Research Division. “This calls for urgent and very strong actions to limit the emission of those greenhouse gasses.”

In 2014, the average global atmospheric carbon dioxide level rose to 397.7 parts per million, substantially higher than the 278 parts per million floating in the atmosphere during preindustrial time, or before 1750. The researchers reported that the annual average is expected to pass 400 parts per million in 2016.

But Dr. Tarasova noted that exceeding the 400 mark does not denote an immediate catastrophe.

“There is nothing magic about 400, it’s nothing better than 399 or 401,” she said. “This is like our obligation to ourselves, we’d like to not go over 400. It’s symbolic.” She said that surpassing the threshold “only shows that our commitments are not there.”

In 2014, methane in the air increased by nine parts per billion over 2013, which represented two and a half times its preindustrial levels. Nitrous oxide reached 1.1 parts per billion more than its levels in 2013, an increase of 20 percent from its preindustrial levels, according to the findings.

The report also noted interactions between greenhouse gas emissions and water vapor in the atmosphere. Humans produce carbon dioxide that heats up Earth’s surface, which then heats up the atmosphere.

Hotter air can hold more moisture, which exacerbates greenhouse warming. According to Dr. Tarasova, if carbon dioxide levels reach 560 parts per million, or double their preindustrial levels, the feedback loop would cause water vapor and clouds to increase atmospheric warming to a rate that is three times as much as what the human-caused gases can do by themselves.

“We shouldn’t blame water vapor for making this place warmer,” she said. Rather, she said, by limiting the emissions of carbon dioxide, nitrous oxide and methane, people can balance the feedback loop and mitigate future warming.

Source: New York Times
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