Year Begins Above The 400 PPM Mark - "Many Months" More Likely In 2015
The new year has only just begun, but we’ve already recorded our first days with average carbon dioxide levels above 400 parts per million, potentially leading to many months in a row above this threshold, experts say.
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The 400 ppm mark was first passed on May 9, 2013. In 2014, it happened two months earlier, in March. The average CO2 concentrations for March, April and June 2014 were all above 400 ppm, the first time that has been recorded. The peak CO2 measurement of 2014 was just shy of 402 ppm in May.
While the 400 ppm mark is somewhat symbolic (as the increase in warming between 399 ppm and 400 ppm is small), it is a large increase from pre-industrial CO2 concentrations, which were around 280 ppm. The progressively earlier occurrence of these high CO2 levels — not seen in somewhere between 800,000 and 15 million years — points to the inexorable buildup of heat-trapping gas in the atmosphere as human emissions continue unabated. That increase in CO2 and other greenhouse gases has raised Earth’s average temperature by 1.6°F since the beginning of the 20th century. Some scientists say that to avoid the worst consequences of climate change, that warming needs to stay under 2°C, or 3.6°F.
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NOAA’s own CO2 record-keeping varies slightly from the Scripps numbers, coming it at nearly 400 ppm. The differences are due to different methods of dealing with the data, though those differences are quite small, Keeling said. Tans initially expected February to be the first month of the year above 400 ppm, but predicting that threshold is tricky because CO2 concentrations depend both on emissions and natural ecosystem processes, which can be influenced by climate phenomena like the El Nino Southern Oscillation cycle, he said.
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http://www.climatecentral.org/news/2015-begins-with-co2-above-400-ppm-mark-18534
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