Concentrations in the atmosphere of the three main global warming gases rose in 2012 to the highest on record, increasing impacts of climate change including ice melt and rising sea levels, the United Nations said.
Carbon dioxide, responsible for about 80 percent of the warming effect of greenhouse gases, gained 0.56 percent to 393.1 parts per million molecules of air, the UN World Meteorological Organization said today in an e-mailed bulletin. The methane concentration increased 0.33 percent and the nitrous oxide level climbed 0.28 percent.
Increasing levels of the gases are at odds with the UN-endorsed goal of keeping the temperature rise since pre-industrial times to below 2 degrees Celsius (3.6 degrees Fahrenheit). The World Bank says the Earth is on track to warm by 4 degrees, and UN scientists said Sept. 27 that humans have already emitted more than half the carbon compatible with the temperature target.
The observations “highlight yet again how heat-trapping gases from human activities have upset the natural balance of our atmosphere,” WMO Secretary-General Michel Jarraud said in the statement. “As a result of this, our climate is changing, our weather is more extreme, ice sheets and glaciers are melting and sea levels are rising.”
Climate treaty envoys from more than 190 nations will gather in Warsaw next week for two weeks of talks to try to help craft by 2015 a legally binding global deal to cut greenhouse gases.
Pledges made by nations to curtail emissions between now and 2020 are insufficient to keep to a 2-degree pathway, the UN Environment Program said yesterday. At best, greenhouse-gas output by the end of this decade will be about 18 percent above levels needed, it said.
If countries take a “business-as-usual” approach, total warming since industrialization may reach 4.6 degrees by 2100, with “devastating” consequences, Jarraud said.
The methane concentration in 2012 was 1,819 parts per billion molecules of air, according to the WMO bulletin. The nitrous oxide concentration was 325.1 parts per billion.