Greenhouse Gas Levels Keep Accelerating
Weekly CO₂ levels at Mauna Loa, Hawaii, recently reached 413.77 ppm, while – several times recently – daily average levels exceeded 414 ppm and hourly levels exceeded 415 ppm.
Current CO₂ levels far exceed levels that were common during the past 800,000 years.
Next to carbon dioxide, there are further greenhouse gases. Methane is important, because of its high short-term potency as a greenhouse gas and because methane levels in the atmosphere have hugely risen since 1750, and especially recently, as illustrated by the image on the right.
Carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) levels in the atmosphere in 2017 were, respectively, 257%, 146% and 122% their 1750 levels.
A recent study concludes that, since sudden collapse releases more carbon per square metre because it disrupts stockpiles deep in frozen layers, and since abrupt thawing releases more methane than gradual thawing does, the impact of thawing permafrost on Earth’s climate could be twice that expected from current models.
Furthermore, there is a huge and growing danger of large abrupt methane releases from clathrates contained in sediments at the seafloor of the Arctic Ocean.
Next to carbon dioxide and methane, there are further greenhouse gases, of which nitrous oxide is particularly important. Nitrous oxide is up to 300 times as potent as a greenhouse gas as carbon dioxide and has a lifetime of 121 years. Several recent studies point at the danger of huge releases of nitrous oxide from permafrost.
According to a 2017 study by Voigt et al., Arctic permafrost contains vast amounts of nitrogen (more than 67 billion tons). Warming of the Arctic permafrost is accelerating, causing rapid thaw of permafrost soils, and this now threatens to cause huge releases of nitrous oxide to the atmosphere. The study concluded that nitrous oxide emissions in the Arctic are likely substantial and underestimated, and show high potential to increase with permafrost thaw.
A recent study shows that nitrous oxide emissions from thawing Alaskan permafrost are about twelve times higher than previously assumed. A 2018 study points at the danger of large nitrous oxide releases from thawing permafrost in Tibet. Even more nitrous oxide could be released from Antarctica. The danger is illustrated by the image below, which shows that massive amounts of nitrous oxide were recorded over Antarctica on April 29, 2019.
Depletion of the Ozone Layer
In addition to being a potent greenhouse gas, nitrous oxide is also an ozone depleting substance (ODS). As the left panel of the image below shows, growth in the levels of chlorofluorocarbons (CFCs) has slowed over the years, yet their impact will continue for a long time, given their long atmospheric lifetime (55 years for CFC-11 and 140 years for CFC-12). Since nitrous oxide levels continue to increase in the atmosphere, while the impact of CFC-11 and CFC-12 is slowly decreasing over time, the impact (as an ODS) of nitrous oxide has relatively grown, as the right panel of the image below shows.
In conclusion, while it’s important to reduce emissions of all greenhouse gases, reducing emissions of methane and nitrous oxide is particularly important. To reduce all such emissions, the Climate Plan recommends feebates as depicted in the image below.
• Climate Plan
• Permafrost collapse is accelerating carbon release, by Merritt Turetsky et al. https://www.nature.com/articles/d41586-019-01313-4
• Permafrost nitrous oxide emissions observed on a landscape scale using the airborne eddy-covariance method, by Jordan Wilkerson et al.
• Magnitude and Pathways of Increased Nitrous Oxide Emissions from Uplands Following Permafrost Thaw, by Guibiao Yang et al.
• Increased nitrous oxide emissions from Arctic peatlands after permafrost thaw, by Carolina Voigt et al.
• A rise of 18°C or 32.4°F by 2026?
• Care for the Ozone Layer