Last year’s average carbon dioxide concentration crossed a major milestone and will likely stay at or above that level for several generations, the World Meteorological Organization announced Monday.
In 2015, average global CO2 levels for the year surpassed 400 parts per million for the first time, the WMO revealed in its annual Greenhouse Gas Bulletin. Many scientists regard that measurement, which indicates the ratio of carbon dioxide to other gases in the atmosphere, as a climate change touchstone ― though it’s not considered a tipping point.
And the uptick is happening at an alarming rate.
“The increase of CO2 from 2014 to 2015 was larger than that observed from 2013 to 2014 and that averaged over the past 10 years,” the report noted.
CO2 concentrations last year were about 144 percent higher than pre-industrial levels. Other emissions measured in the report, methane and nitrous oxide, were up 256 percent and 121 percent from pre-industrial levels, respectively. Among those, however, CO2 contributes the most to warming and is responsible for about 81 percent of the increase in radiative forcing over the past decade.
The increase was in part fueled by last winter’s El Niño event, which contributed to droughts that reduce the ability of forests and other carbon sinks to absorb excess CO2, but the bulk of the increase is due to unbridled human activities ranging from “growing population, intensified agricultural practices, increase in land use and deforestation, industrialization and associated energy use from fossil sources,” the report noted.