At the current rate of increase, the global annual average CO2 concentration is set to cross the 400 parts per million threshold in 2015 or 2016. Here gas-flaring at an oil platform in the Gulf of Mexico. Photo: Flickr.com/dviDshub/CC BY
Radiative forcing increased by 32 per cent between 1990 and 2012, of wich 25 per cent is due to carbon dioxide. The remaining is from other greenhouse gases.
Carbon dioxide, mainly from fossil-fuel-related emissions, accounted for 80 per cent of global warming since 1990 according to the World Meteorological Organization’s (WMO) latest report from November 2013. Between 1990 and 2012 there was more than a 25 per cent increase in radiative forcing – the warming effect on our climate – because of carbon dioxide (CO2).
Carbon dioxide is the single most important greenhouse gas emitted by human activities such as fossil fuel burning and deforestation. CO2 lingers in the atmosphere for hundreds if not thousands of years and so will determine global mean surface warming by the late 21st century and beyond, states the WMO. “Most aspects of climate change will persist for centuries even if emissions of CO2 are stopped immediately.”
The WMO says that on the global scale, the amount of CO2 in the atmosphere reached 393.1 parts per million in 2012, or 141 per cent of the pre-industrial level of 278 parts per million. The amount of CO2 in the atmosphere increased by 2.2 parts per million from 2011 to 2012, which is above the average 2.02 parts per million per year for the past 10 years, showing an accelerating trend.
According to the WMO, since the start of the industrial era in 1750, the global average concentration of CO2 in the atmosphere has increased by 41 per cent. “Monthly observed concentrations of CO2 in the atmosphere exceeded the symbolic 400 parts per million threshold at several Global Atmosphere Watch stations in the Arctic during 2012. During 2013, hourly and daily concentrations passed this threshold in other parts of the world, including at Mauna Loa, Hawaii, the oldest continuous atmospheric measurement station in the world which is widely regarded as a benchmark site in the Global Atmosphere Watch. 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 400 parts per million threshold in 2015 or 2016.”
The WMO shows that between 1990 and 2012 there was in total a 32 per cent increase in radiative forcing – the warming effect on our climate – due to greenhouse gases. In addition to the 25 per cent increase due to carbon dioxide (CO2) mentioned above, the remaining 7 per cent comes from other heat-trapping long-lived gases such as methane, nitrous oxide, ozone-depleting chlorofluorocarbons (CFCs), as well as hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs).
The total radiative forcing by all long-lived greenhouse gases in 2012 corresponds, according to WMO, to an equivalent CO2 concentration of 475.6 parts per million, compared to 473.0 parts per million in 2011.