There’s a pretty story we tell ourselves about environmental problems: Once you fix them, they immediately start to improve.
Smog works like this. In cities where air quality is a problem, smog tends to worsen on weekdays, because millions of people are commuting and factories are fully productive. On weekends, when fewer people drive, the air tends to clear.
Likewise, when the country chose to address its smog problem, it got better. In 1970, Congress passed the Clean Air Act and told the EPA to start regulating air pollution. Smog across the country began to dissipate, and certain lung conditions became less common. Air pollution is not the problem today that it was in the 1960s and early 1970s because the United States addressed it.
It is a pleasant story. It’s true for some issues. For global warming, it is a fable.
Greenhouse gases released into the atmosphere today will cause the seas to rise for centuries to come, even if those gases leave the atmosphere relatively rapidly, finds a new study published Monday in the Proceedings of the National Academy of Sciences.
The study specifically examined short-lived greenhouse gases like methane. Methane is the main ingredient in natural gas, and it contributes about a third of modern-day global warming. It’s very powerful, trapping heat 25 times more efficiently than carbon dioxide, but it’s also ephemeral. On average, a molecule of methane is absorbed in the soil or destroyed in the atmosphere 12 years after it is emitted. A molecule of CO₂ can float around for centuries.