Greenhouse gas concentrations in the atmosphere hit another record

“Carbon dioxide remains in the atmosphere for hundreds of years and in the ocean for even longer. Past, present and future emissions will have a cumulative impact on both global warming and ocean acidification. The laws of physics are non-negotiable,” Jarraud added.

The WMO Greenhouse Gas Bulletin reports on atmospheric concentrations — and not emissions — of greenhouse gases. Emissions represent what goes into the atmosphere. Concentrations represent what remains in the atmosphere after the complex system of interactions between the atmosphere, biosphere, cryosphere, and the oceans. About a quarter of the total emissions is taken up by the oceans and another quarter by the biosphere, reducing in this way the amount of CO2 in the atmosphere.

The Greenhouse Gas Bulletin provides a scientific base for decision-making. WMO releases it ahead of the UN climate change negotiations in Paris, to be held from 30 November to 11 December. A separate Emissions Gap report, from the United Nations Environment Program, focuses on annual emissions of CO₂.

Atmospheric concentrations
Carbon dioxide (CO₂ ) accounted for about 83 percent of the total increase in radiative forcing by long-lived greenhouse gases over the past decade. The pre-industrial level of about 278 ppm represented a balance between the atmosphere, the oceans, and the biosphere. Human activities such as the burning of fossil fuels has altered the natural balance and in 2014, globally averaged levels were 143 percent of pre-industrial levels. In 2014, global annual average concentration of CO₂ concentrations reached 397.7 ppm with annual increase close to the ten year averaged. The global annual average is likely to pass 400 ppm in 2016.

Methane(CH₄) is the second most important long-lived greenhouse gas. Approximately 40 percent of methane is emitted into the atmosphere by natural sources (for example, wetlands and termites), and about 60 percent comes from human activities like cattle breeding, rice agriculture, fossil fuel exploitation, landfills, and biomass burning. Atmospheric methane reached a new high of about 1833 parts per billion (ppb) in 2014 and is now 254 percent of the pre-industrial level.

Nitrous oxide(N₂O) is emitted into the atmosphere from both natural (about 60 percent) and anthropogenic sources (approximately 40 percent), including oceans, soil, biomass burning, fertilizer use, and various industrial processes. Its atmospheric concentration in 2014 was about 327.1 parts per billion. This is 121 percent of pre-industrial levels. It also plays an important role in the destruction of the stratospheric ozone layer which protects us from the harmful ultraviolet rays of the sun.

Water vapor
Water vapor and CO₂ are the two major greenhouse gases. But it is CO₂  which is the main driver of climate change. Water vapor changes are the so-called feedback mechanisms and happen as a response to the change in CO₂. For a scenario considering doubling of is CO₂ concentration from pre-industrial conditions, that is, from about 280 to 560 ppm, water vapor and clouds globally would lead to an increase in atmospheric warming that is about three times that of long-lived greenhouse gases, according to the Bulletin.

— Read more in “The State of Greenhouse Gases in the Atmosphere Based on Global Observations through 2014,” WMO Greenhouse Gas Bulletin no. 11 (9 November 2015)