Underlockdowns, countries around the world have restricted travel and closed businesses. Flights were grounded and highways deserted. The major slowdown of movement has led to an "extreme" decline in — with daily levels 17% lower compared to averages from last year.
According to a study published Tuesday in the journal Nature Climate Change, daily emissions in early April, when most of the world was under strict lockdown measures, fell to levels last seen in 2006. Lockdowns could lead to an annual decline of up to 7% — the biggest drop since World War II, the researchers say.
Scientists studied lockdown measures in 69 countries that are responsible for 97% of global carbon dioxide emissions, looking at data from key economic sectors. They point to massive decreases in transportation usage and industrial activities during the pandemic as the main sources of the decline.
According to the study, the largest factor was a lack of vehicles on the road, accounting for 43% of the decrease. While's carbon footprint fell by a staggering 60%, that industry only generally accounts for about 3% of yearly global carbon emissions — making its overall impact far smaller than other industries.
While those numbers are significant, carbon dioxide stays in the atmosphere for thousands of years. Scientists warn that even this sharp but relatively brief decline is unlikely to make a meaningful difference in the long run if governments don't makea priority.
"Population confinement has led to drastic changes in energy use and CO2 emissions. These extreme decreases are likely to be temporary though, as they do not reflect structural changes in the economic, transport, or energy systems," Professor Corinne Le Quéré of the University of East Anglia, one of the study's lead authors, said in a press release. "The extent to which world leaders consider climate change when planning their economic responses will influence the global CO2 emissions paths for decades to come."
Researchers said the largest change in emissions came from, followed by the U.S., Europe and India. They expect to see a yearly decline between 4% and 7%, depending on how long various countries remain under lockdown.
Such a large yearly emissions drop is on par with the kind of decrease the globe would need to sustain going forward to achieve the goal set in the Paris climate agreement of keeping the Earth's warming from exceeding 2 degrees Celsius, CBS News meteorologist and climate specialist Jeff Berardelli . But shutting down the economy is obviously not a sustainable way to get there.
"The drop in emissions is substantial but illustrates the challenge of reaching our Paris climate commitments," said Professor Rob Jackson of Stanford University, who co-authored the study. "We need systemic change through green energy and electric cars, not temporary reductions from enforced behavior."
The concern is not unfounded — air pollution in China is alreadynow that lockdown measures there have been lifted. The rebound appears to be driven by industrial emissions, as China has permitted most economic activity to resume.
Moreover, the current crisis could push environmental initiatives farther down the list of people's priorities. Following the Great Recession in 2008, climate change researchers saw a decline in public concern for the environment, most likely driven by economic insecurity. When faced with an immediate threat, like the virus and widespread unemployment, people tend to pay less attention to what they view as a more distant risk, like, Berardelli explained.
But there is some hope that the pandemic may shift people's behaviors permanently. Cities around the world are closing streets for pedestrian traffic,may be the new normal, and electric cars are more popular than ever.
The pandemic is also shining new light on thefor . "Air pollution weakens hearts and lungs and makes the virus stronger," Jackson said. "Clean power coupled with electric cars could give everyone clean air without sheltering at home."
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