The World Meteorological Organization has found that the volume of greenhouse gases in the earth’s atmosphere reached a new high in 2013, mainly due to a surge in carbon dioxide levels
With carbon dioxide levels showing the fastest annual increase since 1984, there were more greenhouse gases in the atmosphere in 2013 than at any time since measurements started. The carbon dioxide concentration reached 396 parts per million (ppm), up from 250 at the start of the Industrial Age in 1750. At this rate, the world is looking at an average temperature increase of over four degrees Celsius by the end of this century.
The Greenhouse Gas Bulletin of the World Meteorological Organization (WMO) showed in its latest issue that between 1990 and 2013 there was a 34% increase in radiative forcing – the warming effect on our climate – because of long-lived greenhouse gases (GHGs) such as carbon dioxide, methane and nitrous oxide.
GHGs prevent the earth from losing heat into space, thus changing the climate. In turn, climate change is already having an adverse effect on farm production worldwide, making droughts, floods and storms more frequent and more severe and raising the sea level. Carbon dioxide – emitted by industrial processes including thermal power generation – is the principal GHG in the atmosphere.
The bulletin says that in 2013, carbon dioxide concentration in the atmosphere was 142% of the pre-industrial era (1750), while the atmospheric concentrations of methane and nitrous oxide were 253% and 121% respectively.
Observations from WMO’s Global Atmosphere Watch network showed that carbon dioxide levels increased more between 2012 and 2013 than during any other year since 1984. Preliminary data indicated that this was possibly due to reduced carbon dioxide uptake by the earth’s biosphere in addition to the steadily increasing emissions.
The bulletin reports on atmospheric concentrations of GHGs but not on emissions. About a quarter of the emissions are taken up by the oceans and another quarter by the
biosphere, thus reducing the amount of carbon dioxide in the atmosphere.
Ocean waters turn more acidic in the process, with far-reaching adverse impacts. Marine organisms such as corals, algae, molluscs and some plankton depend on carbonate in the water to build their skeletons. With carbonate availability going down due to acidification, their survival is at risk. The current rate of ocean acidification appears to be the highest in the last 300 million years, according to the report. The acidity increase is already measurable as oceans take up about four kg of carbon dioxide per day per person.
“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 WMO Secretary-General Michel Jarraud.
“The Greenhouse Gas Bulletin shows that, far from falling, the concentration of carbon dioxide in the atmosphere actually increased last year at the fastest rate for nearly 30 years. We must reverse this trend by cutting emissions of carbon dioxide and other greenhouse gases across the board. We are running out of time.”
“Carbon dioxide remains in the atmosphere for many 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.”
Carbon dioxide accounted for 80% of the 34% increase in extra heating by long-lived GHGs from 1990 to 2013, according to the US National Oceanic and Atmospheric Administration’s Annual Greenhouse Gas Index.
On the global scale, the amount of carbon dioxide in the atmosphere reached 396 ppm in 2013, up by 2.9 ppm from 2012. At the current rate of increase, the global annual average carbon dioxide concentration is set to cross the symbolic 400 ppm threshold in 2015 or 2016.
Methane is the second most important long-lived GHG. Approximately 40% of methane is emitted into the atmosphere by natural sources such as wetlands and termites, and about 60% comes from human activities like cattle breeding, rice agriculture, fossil fuel use, landfills and biomass burning. Atmospheric methane concentration reached a new high of 1,824 parts per billion (ppb) in 2013, due to increased emissions from human sources. After a temporary levelling-off, atmospheric methane concentration has been increasing again since 2007.
Nitrous oxide – another GHG – is emitted from both natural (about 60%) and human sources – including oceans, soil, biomass burning, fertiliser use, and various industrial processes. Its atmospheric concentration in 2013 was 325.9 ppb. Its impact on climate, over a 100-year period, is 298 times greater than equal emissions of carbon dioxide. This is of concern as the gas also plays an important role in the destruction of the stratospheric ozone layer which protects us from the harmful ultraviolet rays of the sun.