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Greenhouse Gas Levels Reach World Record

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Concentrations of carbon dioxide, methane, and nitrous oxide in the atmosphere in 2012 reached the highest levels ever recorded, according to a new report issued by the World Meteorological Organization. Wikimedia Commons/Dori

The World Meteorological Organization releases data revealing that carbon dioxide in the atmosphere reached record levels in 2012, and 2013 is likely to rank among hottest years on record.

November 19, 2013—Concentrations of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in the atmosphere in 2012 reached the highest levels ever recorded, according to a new report issued by the World Meteorological Organization (WMO), in Geneva, Switzerland. The levels top the previous record, set in 2011.

The WMO is an intergovernmental organization comprising 191 members. The organization traces its roots to the 1873 founding of the International Meteorological Organization. In 1950, that group was brought under the umbrella of the United Nations, where it serves as a specialized arm for meteorology, hydrology, and geophysical sciences.

The atmospheric concentration levels were published in the WMO Greenhouse Gas Bulletin. The measurements were recorded by WMO’s Global Atmosphere Watch (GAW) program—a complex network of 29 global monitoring stations and more than 400 regional stations dispersed around the globe and hosted by more than 80 countries.

The globally averaged CO2 level was 393.1 parts per million (ppm), an increase of 2.2 ppm from 2011 levels, a 0.56 percent increase. This increase is higher than the yearly average in the past 10 years. This places CO2 levels at 41 percent above preindustrial era levels in 1750. At some observation centers in the Arctic, monthly CO2 levels exceeded 400 ppm, a symbolic threshold. Recently, that threshold has also been exceeded in hourly and daily observations in Hawaii.

“The value of 400 parts per million in one hand has a symbolic meaning as an alarm threshold,” said Oksana Tarasova, a scientific officer for the WMO, in written comments to Civil Engineering online. “There also discussions among scientist that reaching 400 parts per million of global CO2 may enforce a number of feedback processes in the climate system.

“In 1750, which is considered as the beginning of the industrial era, CO2 was 278 part per million. During the last 800,000 years, CO2 fluctuated between about 180 parts per million during ice ages and 280 parts per million during interglacial warm periods. Today’s rate of increase is more than 100 times faster than the increase that occurred when the last ice age ended,” Tarasova said.

Carbon dioxide is the most prevalent greenhouse gas, a primary source being the combustion of fossil fuels. It is responsible for an estimated 64 percent of the radiative forcing—the difference between the radiant energy that enters the atmosphere and the radiant energy that exits. In recent decades it has been blamed for a growing percentage of radiative forcing—approximately 84 percent in the past 10 years.

Methane levels also increased to record concentrations in 2012, reaching 1819 parts per billion (ppb). The WMO estimates that 40 percent of methane in the atmosphere comes from natural sources; 60 percent is the result of agriculture, fossil fuel exploration, biomass burning, and other human activities. The levels of methane observed in 2012 represent a 160 percent increase from levels in 1750.

Nitrous oxide, a less potent and more naturally occurring greenhouse gas, reached 325 ppb in 2012, representing a 20 percent increase from preindustrial levels. That represents an increase of 0.9 ppb, which is slightly higher than the 10-year average rate of growth.

“The observations from the WMO’s extensive Global Atmosphere Watch network highlight yet again how heat-trapping gases from human activities have upset the natural balance of our atmosphere and are a major contribution to climate change,” said the WMO’s secretary-general, Michel Jarraud, in a press release announcing the findings. “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.”

Also in November, the WMO released a preliminary examination of global temperatures for January through September, finding that 2013 is on pace to be one of the 10 warmest years recorded since 1850. The first nine months of 2013 ties 2003 as the seventh-warmest on record, reversing a cooling trend in 2011 and 2012, when La Niña conditions prevailed.

The WMO notes that 2013 has been marked by sharp weather variations, with colder than normal temperatures in Europe, parts of the United States, Russia, and Japan; at the same time, extreme heat baked Australia and melted ice in the Arctic.

Arctic ice melted to just 5.10 million sq km in 2013, a figure that is 18 percent below the recent average. This level places the year as having the sixth-smallest ice coverage on record, though still well in excess of the 3.41 million sq km recorded in 2012. Likewise, ice melt rates in Greenland moderated from record levels in 2012.

“With some natural variability between years, Arctic sea ice is steadily declining at an average rate of 13.7 percent per decade,” said Jessica Blunden, the scientific coordinator of the provisional climate statement, who provided written comments to Civil Engineering online. “The last seven years have seen the lowest Arctic sea ice extents on record. Melting of Arctic sea ice, along with glaciers and ice sheets, contribute to sea level rise.”

Conversely, Antarctic sea ice continues to set records for growth. The 19.47 million sq km of Antarctic seas ice recorded on September 22 broke a record set in 2012 and is 2.6 percent higher than the recent average for ice cover.

“The maximum Antarctic sea ice extent has been increasing at an average rate of 1.1 percent per decade,” Blunden said. “While the last two years have seen the largest maximum extents on record, there is no obvious trend in the increase.” The rate of increase doesn’t offset ice loss in the Arctic, she added.

“Temperatures so far this year are about the same as the average during 2001-2010, which was the warmest decade on record,” said Jarraud. “All of the warmest years have been since 1998 and this year once again continues the underlying, long-term trend. The coldest years now are warmer than the hottest years before 1998.

“Atmospheric concentrations of carbon dioxide and other greenhouse gases reached new highs in 2012, and we expect them to reach unprecedented levels yet again in 2013. This means that we are committed to a warmer future,” Jarraud said. “Surface temperatures are only part of the wider picture of our changing climate. The impact on our water cycle is already becoming apparent—as manifested by droughts, floods, and extreme precipitation.”



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