Carbon dioxide levels hit new record

Atmospheric concentrations of carbon dioxide have recorded a new high, with the monthly average in May touching 424 parts per million, a new update from National Oceanic and Atmospheric Administration of the United States said.

The current concentrations are now more than 50 per cent higher than the pre-industrial times, it said.

Carbon dioxide is the most common among greenhouse gases responsible for causing global warming that is leading to climate change. Other major greenhouse gases are methane, nitrous oxide, a set of fluorinated gases like HFCs and HCFCs, and ozone. Carbon dioxide, generated during the process of burning fossil fuels, accounts for over 70 per cent of all human-induced greenhouse gas emissions.

The NOAA update said the average monthly concentration in May this year was about 3 parts per million higher than May of last year.

Scientists have been able to estimate carbon dioxide concentration levels till about 400,000 years in the past, mainly through the study of polar ice cores that have remained unchanged for millions of years. In this period, CO2 concentrations have remained around 200 ppm during the ice ages, and about 280 ppm during the warmer inter-glacial periods. The monthly average crossed the 400 ppm mark for the first time in May 2013.

But since the middle of last century, CO2 levels have remained at unprecedented levels and have been rising rapidly. In May of 1990, the year that is generally considered as the start of a phase of climate awareness and response, monthly average concentrations of CO2 was around 357 ppm, according to data from the Mauna Loa Observatory in the United States which has been making direct observations of carbon dioxide and other gases since the 1950s.

The monthly average crossed the 400 ppm mark for the first time in May 2013. Data shows that the concentrations were growing at less than 1 ppm per year in the decade between 1960 and 1970, but this rate of growth has increased to nearly 2.5 ppm per year after 2010. This year it has grown by 3 ppm.