You've seen the tweets or witnessed the changes firsthand. With COVID-19 lockdowns in place, skies over cities around the world were bluer. The notoriously dirty air in New Delhi was cleaner, and the canals in Venice were so clear you could see the marine life swimming through them.
The catchphrase "The Earth is healing, we are the virus," was immortalized as a meme.
The observations weren't just anecdotal. A May study found significant drops in daily global carbon dioxide emissions, with a peak decline of 17% in early April. But if the coronavirus pandemic is giving the Earth a breath of fresh air, it may only be temporary. As lockdown orders lift across the globe, experts have warned emissions will quickly rebound. As we resume everyday tasks, any environmental progress can be undone just as quickly as it arrived.
That is, unless policymakers, governments and other groups start working on the structural and societal changes needed to tackle climate change. That includes embracing flexible work-from-home schedules to reduce traffic, closing down streets to vehicles, encouraging the use of bicycles and increasing investments in clean energy.
"This is the right moment to make drastic changes," said Francisco Artigas, director of the Meadowlands Environmental Research Institute in New Jersey. "We have to start engineering ourselves out of the way we live, because it's just not sustainable."
As governments make investments to restart the economy, it's critical they think about promoting advancements like electric vehicles and renewable energy, which create jobs while helping the planet, adds climate scientist Corinne Le Quéré, a professor at the University of East Anglia. If they bail out car or airline industries, for example, they should do so under the condition that companies produce electric vehicles within a certain time frame.
European Union lawmakers in June approved rules ensuring investments won't support polluting industries. The Commission is looking at ways the rules can support the European Green Deal, which aims to eliminate net emissions of greenhouse gases by 2050. The US has not yet unveiled any similar measures in light of the COVID-19 pandemic.
"The changes seen during the lockdown are not structural changes," said Le Quéré, who co-authored the May study on daily carbon emissions, published in the scientific journal Nature Climate Change. "They never were going to last."
With the many deadly and destructive effects of the coronavirus pandemic -- including more than half a million deaths worldwide, mass unemployment, business closures and strains on the US health care system -- there has also been some progress. In China, for instance, air pollution plummeted in February during the country's lockdown period. But the world's most populous country, with nearly 1.4 billion people, also demonstrates why swift action is critical: Air pollution in China had already risen by May after restrictions were lifted. It returned to 2019 levels by June.
As the US continues to loosen restrictions and more businesses reopen, scientists anticipate air pollution and daily emissions will also quickly rise.
"We saw enormous declines temporarily, but things are inching back towards normal," said Rob Jackson, a climate scientist at Stanford University and a co-author of the Nature study.
Because the drop in daily emissions was due to forced behavioral change -- with people being ordered to stay at home by governments -- rather than because of systemic change, it wasn't designed to last, Jackson says. Total miles driven in the US, for instance, fell by more than 40% in March before climbing again as more Americans returned to the road, even before restrictions were lifted. There have also been significant drops in air travel, with the Federal Aviation Administration reporting in mid-May that the number of commercial flights operating in the US had dropped 71% compared to the same time last year.
To effectively tackle climate change, Le Quéré says, there needs to be systemic change to the energy infrastructure, such as a stronger focus on green energy and also behavioral change aimed at improving an individual's well-being. Doing things like biking and walking instead of driving, as well as eating less red meat, aren't only good for the environment, they're also good for personal health.
"These are behavior changes that are not so brutal and fast," she said.
One of the biggest shifts in behavior during the lockdown has been the exponential rise in people working from home. About half of American workers are telecommuting, according to an April report from the Brookings Institution, a nonprofit public policy organization in Washington, DC. That's more than twice as many as were working from home in 2017-18. Climate scientists hope that's a trend that continues to some degree even after the pandemic ends, perhaps with some people staying home permanently. Fewer people on the road means less pollution from vehicles.
"We have had false starts before on telecommuting," Artigas said. "But maybe the pandemic will make a difference."
Meanwhile, many people who can't work from home are rethinking their commutes in the age of social distancing. Riding a crowded train, for instance, is a lot less appealing during a pandemic. Several cities around the world, including Milan and Paris, are reimagining their transit services by adding bike lanes and wider sidewalks. Seattle has permanently closed several roads to promote bike and pedestrian traffic.
"We realize that as things start to open up again, people are still going to need to get around and transit isn't going to play exactly the same role it used to," said Ethan Bergerson, a spokesman for the Seattle Department of Transportation. "We still want people to have those good, safe options to get around without a car and we want to do whatever we can to encourage it."
But a push to socially isolate in cars or seek space on the sidewalk means that COVID-19 could potentially have a detrimental effect on public transit infrastructure and investment. In the San Francisco Bay Area, several bus lines are on the chopping block as transit budgets dwindle and ridership plummets. Other cities like Los Angeles and Washington, DC, have also made significant cuts to bus and rail service amid decreases in revenue and ridership.
The drop in carbon emissions during the lockdown, though significant, still isn't enough to impart long-lasting change. Scientists say that won't happen until we bring emissions down to net zero, meaning we remove as much carbon from the atmosphere as we release.
In fact, carbon dioxide levels still hit a record high this year, according to data from the Scripps Institution of Oceanography and the National Oceanic and Atmospheric Administration. May saw the highest monthly average amount of CO2 in the air ever recorded, at around 417 parts per million.
"We're still emitting," said Ralph Keeling, Scripps CO2 program director. "A short-term reduction like this doesn't make that much difference in the long run, unless it's followed up by a change in trajectory where we start to emit less year-on-year. The compound effect of that is what we need to make a course change."
It's easy to be pessimistic. Even with a global lockdown, one could think, we still couldn't lower emissions enough to meet environmental goals. But that's not how we should be looking at the issue, says Dan Cohan, associate professor of civil and environmental engineering at Rice University. Instead, we should be focused on implementing sustainable environmental measures, especially now that things are opening up again.
"If the lesson gets mistaken as assuming the path to a cooler planet is going to come from everybody staying home, that's not a sustainable path," he said. "This has a danger of people conflating emissions reductions with economic destruction."
Tech companies are also taking steps to tackle climate change. Last week, Apple said it planned to become carbon neutral across its entire business by 2030. Microsoft also teamed up with major companies including Nike, Unilever and Starbucks to form Transform to Net Zero, an initiative geared toward achieving net zero carbon emissions by 2050. In January, Microsoft CEO Satya Nadella said the company aims to become carbon negative by 2030 and seeks to undo by 2050 the greenhouse gas emissions it's sent into the Earth's atmosphere over the company's lifetime.
Cohan says stabilizing the climate will involve growing the economy, as there'll need to be investments in measures like replacing fossil fuels with cleaner forms of energy.
A long-term value of the lockdown so far is that it's provided a peek into how changed behavior can help reverse damage to the environment. Fewer cars on the road, for instance, shows what's possible if more people choose to walk, bike or drive electric cars. The decline in coal use -- which began in the US far before the pandemic -- also paints a picture of the impact that more green measures, like wind and solar energy, can have on the planet.
"Even though the changes have been incredible," Artigas said, "there's a long way to go."