Carbon dioxide concentration surges

View from Manua Loa observatiry, where CO2 concentrations greater than 400 ppm have been recorded both in 2013 and 2014.

The concentration of carbon dioxide in the atmosphere increased last year at the fastest rate for nearly 30 years, according to the latest data from the WMO.

The World Meterological Organization (WMO) reported in September 2014 that the amount of greenhouse gases in the atmosphere reached a new record high in 2013, propelled by a surge in levels of carbon dioxide. 

“We must reverse this trend by cutting emissions of CO2 and other greenhouse gases across the board,” said WMO Secretary-General Michel Jarraud. “We are running out of time.”

Between 1990 and 2013 there was a 34 per cent increase in radiative forcing – the warming effect on our climate – because of long-lived greenhouse gases such as carbon dioxide (CO2), methane and nitrous oxide.

In 2013, the concentration of CO2 in the atmosphere was 142 per cent of the pre-industrial era (1750), while concentrations of methane and nitrous oxide were 253 per cent and 121 per cent of pre-industrial levels respectively.

CO2 levels increased more between 2012 and 2013 than during any other year since 1984. The WMO says that this was possibly related to reduced CO2 uptake by the earth’s biosphere in addition to the steadily increasing CO2 emissions.

The atmospheric concentrations represent what remains in the atmosphere after the complex system of interactions between the atmosphere, biosphere and the oceans. About a quarter of the total emissions are taken up by the oceans and another quarter by the biosphere, thus reducing the amount of CO2 in the atmosphere.

The ocean cushions the increase in CO2 that would otherwise occur in the atmosphere, but with far-reaching impacts. The current rate of ocean acidification appears unprecedented at least over the last 300 million years, according to the WMO analysis.

The WMO general secretary said: “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. The concentration of carbon dioxide in the atmosphere actually increased last year at the fastest rate for nearly 30 years. Carbon dioxide remains in the atmosphere for many hundreds of years and in the ocean for even longer. Past, present and future CO2 emissions will have a cumulative impact on both global warming and ocean acidification. The laws of physics are non-negotiable.” 

Annual carbon dioxide concentrations in the Earth’s atmosphere are very close to reaching 400 parts per million for the first time in three million years. At the current rate of increase, the global annual average CO2 concentration is set to cross the symbolic 400 parts per million threshold in 2015 or 2016 according to WMO. Instruments at the Mauna Loa Observatory in Hawaii recorded daily atmospheric levels of carbon dioxide greater than 400 parts per million in spring 2013 and 2014.

The Mauna Loa carbon dioxide (CO2) record, also known as the “Keeling Curve,” is the world’s longest unbroken record of atmospheric carbon dioxide concentrations. This record, from the Mauna Loa Observatory , near the top of Mauna Loa on the big island of Hawaii, shows that carbon dioxide has been increasing steadily from values around 317 parts per million (ppm) when Charles D. Keeling began measurements in 1958, to nearly 400 ppm today.

Geologist Ralph Keeling, director of the CO2 and O2 measurement programmes, said that the next significant milestone to be passed will be monthly averages in excess of 400 ppm. Fossil fuel burning continues to increase concentrations of the greenhouse gas to levels not seen in human history and not in perhaps as many as three to five million years.

“We’re already seeing values over 400,” said Keeling. “It’s just a matter of time before it stays over 400 forever. At this pace we’ll hit 450 ppm within a few decades.”

In the Pliocene era, the last time that CO2 reached the symbolic milestone of 400 parts per million in the atmosphere, temperatures rose by between three and four degrees and sea levels were between five and 40 metres higher than today. 

Reinhold Pape

Edited from WMO press release 9 September 2014 and Scripps measurements notes 17 March 2014

Facts on atmospheric concentrations

Carbon dioxide (CO2) accounted for 80 per cent of the 34 per cent increase in radiative forcing by long-lived greenhouse gases from 1990 to 2013, according to the U.S. National Oceanic and Atmospheric Administration (NOAA) Annual Greenhouse Gas Index.
On the global scale, the amount of CO2 in the atmosphere reached 396.0 parts per million in 2013. The atmospheric increase in CO2 from 2012 to 2013 was 2.9 parts per million, which is the largest annual increase for the period 1984–2013. Concentrations of CO2 are subject to seasonal and regional fluctuations. At the current rate of increase, the global annual average CO2 concentration is set to cross the symbolic 400 parts per million threshold in 2015 or 2016.

Methane (CH4) is the second most important long-lived greenhouse gas. Approximately 40 per cent of methane is emitted into the atmosphere by natural sources (e.g., wetlands and termites), and about 60 per cent comes from human activities like cattle breeding, rice agriculture, fossil fuel exploitation, landfills and biomass burning. Atmospheric methane reached a new high of about 1824 parts per billion (ppb) in 2013, due to increased emissions from anthropogenic sources. Since 2007, atmospheric methane has been increasing again after a temporary period of levelling off.

Nitrous oxide (N2O) is emitted into the atmosphere from both natural (about 60%) and anthropogenic sources (approximately 40%), including oceans, soil, biomass burning, fertilizer use, and various industrial processes. Its atmospheric concentration in 2013 was about 325.9 parts per billion. Its impact on climate, over a 100-year period, is 298 times greater than the same emissions of carbon dioxide. 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.

Ocean acidification: The ocean currently absorbs one-fourth of anthropogenic CO2 emissions, reducing the increase in atmospheric CO2 that would otherwise occur because of fossil fuel combustion. Enhanced ocean CO2 uptake alters the marine carbonate system and leads to increasing acidity. The ocean’s acidity increase is already measurable as oceans take up about four kilogrammes of CO2 per day per person.

The current rate of ocean acidification appears unprecedented at least over the last 300 million years, based on proxy-data from paleo archives. In the future, acidification will continue to accelerate at least until mid-century, based on projections from Earth system models.

The potential consequences of ocean acidification on marine organisms are complex. A major concern is the response of calcifying organisms, such as corals, algae, molluscs and some plankton, because their ability to build shell or skeletal material (via calcification) depends on the abundance of carbonate ions. For many organisms, calcification declines with increased acidification. Other impacts of acidification include reduced survival, development and growth rates, as well as changes in physiological func-tions and reduced biodiversity.

Atmospheric CO2 at the Manua Loa Observatory, Hawaii.

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