In the last post we wrote about carbon dioxide, the #1 cause of global warming. But methane, the #2 contributor, is not exactly negligible. It’s caused 20% of global warming so far. Each molecule is much more important than CO2: around 30 times as much if considered on a 100 year timescale.
Methane concentrations (as measured in ice cores and direct measurement) have also skyrocketed since preindustrial times:
Compare methane with carbon dioxide, which has risen by 45% since preindustrial times. Methane reached a 45% larger level than its preindustrial concentration back in the 1920s! There’s now over 2.5 times the methane in the air than in preindustrial times. Methane has much smaller concentration than CO2 — 2 ppm vs 400 ppm.
There was some indication recently that concentrations were leveling off, but CH4 is back on the rise since 2006:
Natural gas is mostly methane, and so is swamp gas, which is produced in wetlands by tiny microorganisms called methanogens. Methanogens work well in warm, wet, low-oxygen environments, so wetlands or flooded rice patties are big sources. So are the bellies of cows, sheep, and goats — and even termites! Methane is a big reason why beef has such a high carbon footprint.
There’s a lot of methane locked up in permafrost and ice in the Arctic, and there’s also huge amounts of frozen organic material that’s ripe for decomposition by methanogens. Certain Arctic lakes have methane bubbling to the top, where they can be lit on fire! There’s concern about these sources releasing or creating more methane as the climate warms, leading to an amplifying feedback that causes even more warming. Scientists are closely monitoring methane emissions in the Arctic, and worldwide, to identify potential surprises.
However, it’s quite difficult to estimate with precision how much methane comes from different sources. Estimates from the individual sources on the ground don’t add up to the atmospheric increase/sinks. Different groups provide their own estimates of the sources, three of which are shown below (GAINS-ECLIPSE5a and EDGARv4.2EXT from the Global Methane Project spreadsheet and CEDS).
Why would methane concentrations have stabilized starting in 2000, and accelerated in 2006, if there were no matching trends in the anthropogenic emissions? Scientists are still arguing about that one, but it could be that natural wetland sources have changed, that concentration of the hydroxyl radical (the main way methane breaks down) in the atmosphere has changed, or that we haven’t accounted all the sources well enough.
About those anthropogenic sources. Leaking coal mines, natural gas wells, and pipelines contribute a tremendous amount to methane emissions, and have risen sharply since the early 2000s (data from CEDS):
For example, the Aliso Canyon natural gas storage facility in Los Angeles began spewing tons of methane (watch infrared video footage here) and other chemicals in October 2015. Local residents began suffering from headaches, nose bleeds, and other illnesses, and eventually thousands of families were forced to evacuate. The leak wasn’t capped until February 2016, by which time over 100,000 tons of methane had leaked.
There is little government oversight on these wells, and industry self-regulation is not exactly stellar. Check out this article for descriptions of some of the utter failures of risk management in the industry. SoCalGas recently agreed to a $119M settlement, which will go to offsetting methane emissions across the state, a long-term health study of affected residents, and environmental justice-related projects, among other projects.
Imagine 1500 Aliso Canyon blowouts each year. That’s the best estimate of fugitive methane leakage from coal, oil, and natural gas facilities across the world. Could we be doing a better job at detecting leaks? The Environmental Defense Fund plans to launch their own satellite called MethaneSAT for much-needed oversight on fugitive fossil fuel emissions.
The waste category includes methane released from landfills and water treatment. Note this source has more than doubled since 1970. There are ways to mitigate these, e.g., capturing biogas from landfills or installing methane digesters to water treatment facilities. And we shouldn’t forget (gasp!) creating less waste.
Rice is typically grown in flooded fields, which create anoxic conditions that methanogens love. There are well-known methods to reduce these emissions and grow more efficiently at the same time.
Finally, animal agriculture is another major source of methane, specifically ruminants that have multiple stomachs for digestion. Cows, goats, and sheep all burp out large amounts of methane in their digestive system. There simply wouldn’t be nearly as many cattle on the planet if it wasn’t for our appetite for beef. When combined with the inherent inefficiency of animals as a calorie source (it takes 30 pounds of feed to create 1 pound of beef, per the USDA), the meat industry has an extremely high carbon footprint.
Are we shifting towards less meat intensive diets? Definitely not — as the world becomes more rich, more and more people are demanding more meat in their diet. Projections suggest that satisfying the demand for more meat is the main challenge for feeding the world in future decades, not rising populations.
The future doesn’t have to be like these projections though. That’s why we’re making Flourish. If you want to support our efforts to build this game, you can donate to the EarthGames Support Fund. Donations right now would go hiring a paid student research assistant.