Concentrations of greenhouse gases in the atmosphere continue to break records, with global average carbon dioxide concentrations reaching 397.7 parts per million in 2014, the World Meteorological Organization (WMO) says.
“We will soon be living with globally averaged CO2 levels above 400 ppm as a permanent reality,” says WMO Secretary-General Michel Jarraud.
Two other key greenhouse gases also set records in 2014. Methane levels were 1,833 parts per billion and concentrations of nitrous oxide reached 327 ppb, says WMO, the United Nations agency considered the world’s scientific authority on Earth’s atmosphere.
Radiative forcing—a warming effect—from greenhouse gases increased 36% between 1990 and 2014, WMO says. The organization points out that warming caused by climbing CO2 concentrations has led to an increase in the level of water vapor, which is also a greenhouse gas. Warmer air holds more moisture, WMO explains.
“We have to act now to slash greenhouse gas emissions if we are to have a chance to keep the increase in temperatures to manageable levels,” Jarraud warns.
Global diplomatic talks to cut those emissions are under way and are expected to produce a new climate change treaty in Paris next month. Thus far, 160 countries have individually pledged to carry out specific actions to control emissions.
But a scientific assessment of those pledges, conducted by the United Nations Environment Programme (UNEP), says they fall short of what’s needed to hold the global temperature rise to 2 °C by 2100 when compared with preindustrial levels.
Annual global greenhouse gas emissions need to be equivalent to 42 billion metric tons of CO2 in 2030 for at least a 66% chance of meeting that policy goal, UNEP says. Full implementation of all pledges made thus far would lead to emissions equivalent to 52 to 57 billion metric tons of CO2 in 2030, the agency estimates. This level would put the world on track for a temperature rise of about 3 °C by the end of the century, UNEP adds.