Image courtesy of Britannica
Few eyebrows will likely be raised by the World Meteorological Organization's (WMO) latest report, which concluded that levels of atmospheric carbon dioxide and nitrous oxide hit record highs last year. According to the report, carbon dioxide levels rose 0.53% from 2005 to 381.2 ppm while nitrous oxide levels, third among greenhouse gas emissions, rose 0.25% from 2006 to 320 ppb - 36% and 19% above pre-industrial times, respectively.
Perhaps surprisingly - given the recent discovery of significant new sources of methane in arctic regions - the report also found that methane levels actually dipped slightly, 0.06% from 2005 to 1,782 ppb (which is still 155% higher than pre-industrial times). Geir Braathen, WMO's senior scientific officer, explained that scientists' fears that widespread permafrost thawing in Siberia would drastically increase methane concentrations haven't been borne out by the data, a sentiment echoed in an op-ed written by Russian scientist Dmitry Zamolodchikov.While it is possible that methane's impact on global warming may have been overstated, it's likely that the data used in the report doesn't yet encompass the figures obtained in some of the newest studies - many of which estimate that up to 500 Gt of the gas could be trapped within Siberia's permafrost layers. Moreover, there may be other sources of methane that have simply not yet been identified. Zamolodchikov may be right to point out that, in the short term at least, methane may not influence global warming much; over the next few centuries, however, this could well change.
How much of it and how long it will take for this vast amount of methane to be released remains unclear - possibly hundreds of Gt within the span of several centuries. What is evident is that carbon dioxide still has the edge in effecting global warming - according to Braathen, it contributed 91% of the total greenhouse gas heating effect in the past 5 years.