The graph above shows methane concentrations in Earth’s atmosphere over the past 10,000+ years: 8000 BCE to 2018 CE. The units are parts per billion (ppb). The year 1800 is marked with a circle.
Note the ominous spike. As a result of increasing human-caused emissions, atmospheric methane levels today are two-and-a-half times higher than in 1800. After thousands of years of relatively stable concentrations, we have driven the trendline to near-vertical.
Here are 10 things you should know about methane and the climate:
1. Methane (CH4) is one of the three main greenhouse gases, along with carbon dioxide (CO2) and nitrous oxide (N2O).
2. Methane is responsible for roughly 20% of warming, while carbon dioxide is responsible for roughly 70%, and nitrous oxide the remaining 10%.
3. Methane is a powerful greenhouse gas (GHG). Pound for pound, it is 28 times more effective at trapping heat than is carbon dioxide. Though humans emit more carbon dioxide than methane, each tonne of the latter traps more heat.
4. Fossil-fuel production is the largest single source. Natural gas is largely made up of methane (about 90%). When energy companies drill wells, “frac” wells, and pump natural gas through vast distribution networks some of that methane escapes. (In the US alone, there are 500,000 natural gas wells, more than 3 million kilometers of pipes, and millions of valves, fittings, and compressors; see reports here and here.) Oil and coal production also release methane—often vented into the atmosphere from coal mines and oil wells. Fossil-fuel production is responsible for about 19% of total (human-caused and natural) methane emissions. (An excellent article by Saunois et al. is the source for this percentage and many other facts in this blog post.) In Canada, policies to reduce energy-sector methane emissions by 40 percent will be phased in over the next seven years, but implementation of those policies has been repeatedly delayed.
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