The amount of carbon dioxide humans are responsible for generating worldwide each day fell by 17 percent this April compared to the daily average for 2019. The steep drop is a result of the COVID-19 pandemic, according to estimates published today in the journal Nature Climate Change. That gets the world to about the same amount of planet-heating pollution it was pumping out in 2006, showing how much greenhouse gas emissions have grown in just the last 14 years.

Most of the cuts in CO2 came from manufacturing, power generation, and transportation and shipping — excluding aviation. The aviation industry has been particularly hard hit by the pandemic. Aviation’s carbon footprint shrank by 60 percent, but it has a far smaller impact on the climate as a whole compared to other industries.

Scientists and environmentalists, however, aren’t exactly optimistic about the drop in greenhouse gas emissions. The dramatic fall is the result of governments temporarily shutting down businesses and people staying home to avoid spreading the novel coronavirus. But that alone isn’t enough to pump the brakes on climate change. Without more systemic and long-lasting changes to how society operates, pollution could come back with a vengeance once the pandemic subsides.

“Social responses alone, as shown here, would not drive the deep and sustained reductions needed,” the study reads, noting that any benefits the environment is experiencing because of the COVID-19 crisis are probably temporary. The authors looked at data on energy use, industry activity, and government responses to the pandemic to make their estimates.

Total emissions for 2020 are only projected to drop modestly, depending on how long social distancing measures stick around. If carbon emissions are back to where they were before the crisis by mid-June, the pandemic would only have reduced the year’s pollution by roughly 4 percent. If some restrictions stay in place throughout the year — as many public health experts recommend — there could be up to a 7 percent decline, according to study authors. The estimates fall roughly in line with an earlier projection from the International Energy Agency, which forecast a roughly 8 percent drop this year.

Even so, “eight percent is not an awful lot in the grand scheme of things,” Sean Sublette, a meteorologist at the nonprofit Climate Central, told The Verge earlier this month. Carbon dioxide builds up in the atmosphere and can stay there for hundreds or even thousands of years. So the overall amount stuck in the atmosphere trapping heat as a result of human activity over generations is still growing. “It’s like a bathtub and you’ve had the spigot on full blast for a while, and you turn it back 10 percent, but you’re still filling the bathtub,” Sublette said.

If governments delay action on climate change during or after the pandemic, emissions could come roaring back worse than before, like they did after the 2008 financial crisis. That could lead to a climate crisis that’s worse than what was expected before the novel coronavirus emerged.

On the other hand, if that 4 to 7 percent drop in annual carbon dioxide pollution continues each year — not because the pandemic forced us to stay inside, but because of an intentional shift from fossil fuels to renewable energy — that would get us closer to the goals set out in the Paris climate accord, which aims to cut emissions to almost zero by the middle of the century. And that could avert another global disaster brought on by climate change.