<em>The Weekly Planet</em>: What 2020’s Bizarre Economy Taught Us About Climate Change

Instead, the pandemic happened, and emissions fell below 1990 levels in a matter of months. But that tumble downhill only showed how much further we still have to hike: For all the economic upheaval, the U.S. did not reach the goal that, in accordance with the Paris Agreement, it’s meant to hit just four years from now, in 2025.

The math only gets harder for more ambitious targets. President-elect Joe Biden has said that the U.S. should aim to zero out its carbon emissions by 2050. That scale of reduction obviously couldn’t happen in a single year, so analysts have tried to estimate a glide path for getting there. Larsen’s rule of thumb is that by 2030, the U.S. would need to cut emissions to about 40 percent below their historic peak to stay on track.

But last year, amid the pandemic, the U.S. managed a cut of only 21 percent. So the U.S. would need to double 2020’s cuts in less than a decade if we hope to stay on track for net zero.

In other words: “We will need emissions reductions of this scale … for many years to come, and we need to do it differently than we did in 2020,” Larsen said.

Across the economy, the sheer strangeness of the pandemic economy held other climate lessons. Here are three takeaways from 2020 emissions that might help you think about climate change:

1. The good news in a bad report: Coal is crumbling

Generally, emissions declined last year because the economy crumbled. The one exception to that trend is the power sector. Electricity demand declined by only about 2 percent: We used the same amount of electricity as we would in a normal year; we just used it all at home. Yet greenhouse-gas pollution from the power sector fell by 10.3 percent.

Coal’s ongoing decline explains this shift. In 2019, the American coal industry entered a free fall, with coal use dropping 18 percent. Last year, the plunge continued, and coal use fell by almost 19 percent. Renewables and gas made up the difference.

In the past decade, most of the power sector’s emissions declines have come from the coal-to-gas switch. This can make climate advocates nervous, because the climate cannot sustain an indefinite build-out of natural-gas infrastructure. Gas is, after all, still a fossil fuel, and even though it is a cleaner fuel source than coal, its production releases the hyper-heat-trapping pollutant methane.

2. Transportation was gutted by the pandemic

The rest of the 2020 energy system looked more like the transportation sector, which bore the brunt of the pandemic. Transportation emissions fell nearly 15 percent as gasoline and jet-fuel consumption plummeted. Diesel, however, didn’t fall nearly as far, and by December it had returned to its 2019 level.

Larsen sees a lesson in this divergence: Diesel tends to be used to transport goods, so it’s a proxy for economic consumption more widely. But jet fuel and gasoline are used for personal travel. “Rather than the economy shutting down, we still made things and we still moved things around,” she said. “This was really about making people stay in one place.”

Many of 2020’s emissions drops were due to the springtime shutdowns—in most cases, and to Larsen’s surprise, transportation activity had rebounded by the end of the year. Vehicle miles traveled, a metric that tracks how much Americans are driving their personal cars and trucks, reached its low point in April and May, then bounded partway back:

In May, too, jet-fuel demand dropped by 68 percent compared with the year before. But by December it had made up nearly half of that gap.