Southern oceans losing out in the climate war

Researchers have forecasted a fall in the ability of Southern oceans to absorb greenhouse gases from the atmosphere due to increased global warming rate by up to 30% making it more difficult to stabilize man-made carbon dioxide (CO2) levels in the air and increased risk of accelerated global warming effects as published in the International weekly journal, Science.

The scientists from countries including Britain, France and Germany termed the southern oceans as one of the world’s natural “carbon sinks” accounting for 15 per cent of all the carbon taken out of the atmosphere and believed that this rate has declined constantly each decade since 1981 on the basis of a four year study of data from 51 carbon dioxide monitoring stations around the world. This is feared to have been caused by none other than man’s own actions and has happened at least two decades earlier than expected.

Temperatures due to global warming are predicted to rise by almost 1.5C (2.7F) midway of the century, not taking into account any increase in further emissions. Till now, since the industrial revolution, 500 giga-tonnes of carbon dioxide has been stated to be released into the atmosphere through the use of fossil fuels, cement manufacture and changes in land use, a quarter being absorbed by the oceans and the other quarter by vegetation.

“This is serious,” said Corinne Le Quéré, of the University of East Anglia (UEA) and the British Antarctic Survey (BAS), two of the world’s leading environmental research centers and the paper’s lead author. “This is the first time that we’ve been able to say that climate change itself is responsible for the saturation of the Southern Ocean sink. With the Southern Ocean reaching its saturation point more CO2 will stay in our atmosphere. Since the early 1980s the carbon sink hasn’t changed. In the same period the emissions have gone up by 43 per cent.”

The fall in the ability to soak up carbon dioxide emissions from the atmosphere is ascribed to high winds acting on ocean currents, bringing deeper waters that already contain high levels of carbon to the surface leaving the surface more saturated and unable to absorb high portions of CO2. The high winds are believed to have been caused by climatic changes due to combined alterations in the ozone layer and carbon emissions.

The theory behind the strengthening of winds describes how emissions of chemicals such as chlorofluorocarbons (CFCs), along with other chlorine- and bromine-containing compounds have depleted the stratospheric ozone levels, resulting in a massive thinning or "ozone hole" over the Antarctic, in turn producing a cooling 20 to 40 kilometers above the icy surface of the continent, thus increasing the intensity of westerly winds.

Ian Totterdell, a climate modeler at the Met Office Hadley Centre said “This is the first time we have been able to get convincing evidence that a change in the uptake of CO2 by the oceans is linked to climate change. It’s one of many feedbacks we didn’t expect to kick in until some way into the 21st century.”

The team used CO2 measurements in water collected during research cruises in the Southern Ocean in 1998, 2000, 2001 and 2002 to check their calculations. The statistics of the research state that the net quantity of carbon dioxide absorbed by the Southern Ocean from the atmosphere in 1981 was 0.6 billion tonnes but it emitted 0.3 billion tonnes back into it. In 2004 it absorbed 0.8 billion tonnes but emitted 0.5 billion tones.

The southern ocean winds are projected to get more intense in case CO2 emissions continue to be released at the same rate. Current carbon dioxide levels are 383 parts per million (ppm) and climbing at roughly two ppm per year. The IPCC, the European Union and other organizations have also declared 450 ppm as the CO2 level that needs to be stabilized to minimize extreme impacts and risks of global warming.

A secondary finding also revealed that the combination of CO2 and seawater, leading to water becoming acidic, is faster in the Southern oceans, the fourth largest of the world's five oceans, as compared to other oceans where it is believed to affect marine life not before 2050.

Professor Chris Rapley, director of BAS confessed that uncertainties in the research remain but the findings are a cause of worry.

Global warming has not been globally uniform. Some areas (including parts of the southeastern U.S.) have, in fact, cooled over the last century. The recent warmth has been greatest over North America and Eurasia between 40 and 70°N.