U.S. Carbon Emissions Fall Most Since World War II — But Will Likely Bounce Back Quickly, Experts Warn

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Greenhouse gas emissions in the United States fell in record-breaking numbers in 2020 — but experts warn that the data still doesn't mean all is well when it comes to global warming, according to a new report.

U.S. emissions fell by an estimated 10.3 percent this past year, the single largest drop in annual emissions in the post-World War II era, the Rhodium Group said in a report released Tuesday.

The numbers mean that U.S. emissions dropped below 1990 levels for the first time in 30 years, and also far outpaced the then-record 6.3 percent drop in emissions that came along with the Great Recession in 2009.

According to the report, the decline in emissions is largely due to the coronavirus pandemic, as the economic sectors that were hit the hardest — transportation, electric power and industry – are the country's leading sources of greenhouse gas emissions.

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Had COVID-19 not been a factor, emissions likely would only have declined by about 3 percent, the report said.

Though the decline means that the U.S. is likely to far exceed its goals for the 2020 Copenhagen Accord — which were to achieve a 17 percent reduction below 2005 levels — experts warn that the drop shouldn't exactly be celebrated.

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The report emphasized the fact that the reductions were only due to a temporary decrease in economic activity, and not from structural change that could deliver a more long-term, lasting impact.

"With growth expected to bounce back in 2021 (most forecasts currently project GDP growth of 3 to 4 percent), emissions will likely increase as well absent a concerted effort," the report said. "The emission reductions of 2020 have come with an enormous toll of significant economic damage and human suffering. With coronavirus vaccines now in distribution, we expect economic activity to pick up again in 2021, but without meaningful structural changes in the carbon intensity of the U.S. economy, emissions will likely rise again as well."

It also stressed that the decline should not be "considered a down payment" toward the U.S. meeting the levels laid out in the Paris Agreement, which is 26-28 percent below 2005 levels by 2025. Though President Donald Trump removed the U.S. from the agreement, President-elect Joe Biden has pledged to rejoin as soon as he enters office.

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The fact that the declines should not be seen as having a positive effect on the climate is something not only emphasized in the report, but echoed by climate activist Greta Thunberg in a recent chat with PEOPLE.

Thunberg, 18, warned that despite the fact that global CO2 emissions decreased by about 7 percent in 2020, that reduction would eventually be erased.

"Some people might think that this pandemic has had positive effects on the climate, and that, of course, that's far from the truth," she said. "There are no good lessons to learn from this pandemic… [but] it has shown us that we are not living sustainable, and also just shows the importance of science. That we cannot, we will not, make it without listening to the science."