Since the coronavirus lockdown we’ve seen reports of clear waters in Venice, dramatically reduced air pollution in China and stunningly clear views of the Himalayas from 200 kilometres away – a tantalising snapshot of a low-carbon future.
Now scientists from across Europe and the US have teamed up to quantify the fall in emissions that created these scenarios, publishing their findings in the journal Nature Climate Change.
They found that at the peak of confinement on 7 April, overall daily global carbon dioxide (CO2) emissions dropped by 17% compared to mean levels in 2019, while countries saw an average 26% reduction.
Making these calculations proved tricky, says lead author Corinne Le Quéré from the University of East Anglia, UK, due to lack of daily energy data across countries and economic sectors.
Instead, they used activity data for the primary sectors responsible for emitting CO2, including power generation, industry, surface transport, public buildings and commerce, residential buildings and aviation.
Then they calculated how activities changed in each of those sectors under different lockdown scenarios and established the daily level of confinement for 69 countries, enabling them to estimate the change in 97% of global emissions.
Broken down, the results show that reduced surface transport produced the greatest impact, accounting for a 43% drop in emissions, followed by power and industry which together account for another 43% reduction.
Although aviation is most impacted by the lockdown, grounded planes only produced 10% of the lower emissions –because they only emit 3% of the world’s carbon.
Looking ahead, if we return to pre-pandemic levels of mobility and economic activity by mid-June, the overall emissions for 2020 would decline by 4%, but if some restrictions remain in place the average drop could reach 7%.
The daily decrease in emissions takes us back to 2006 levels, way exceeding the normal variability, and the expected annual decrease thwarts anything we’ve seen since the second world war, Le Quéré says.
But the big picture impact on the climate is negligible, she warns.
“This is because climate sees the accumulation of CO2 that we have done for decades. Also, although emissions are decreasing possibly 4-7% this year, we are still emitting over 30 billion tonnes of CO2 this year alone.”
She also notes that the changes are not structural, so emissions are likely to bounce back to pre-confinement levels – in fact, the fall in emissions during the 2008-09 global financial crisis was followed by a huge rebound in 2010.
To produce the changes that are needed to ease the catastrophic effects of climate change, CO2 emissions need to decrease year by year, not just as a one-off. But the pandemic does show what can be achieved – and offers an opportunity to take stock.
“The extent to which world leaders take into account the need to bring emissions down to zero when planning their economic responses to COVID-19 is likely to influence the pathway of CO2 emissions for decades to come,” says Le Quéré.
“There are many actions that can at the same time support workers, improve public health and tackle climate change.”
Surface transport, the sector most impacted by the pandemic, is a shining example, with opportunities to support active transport through walking, cycling and e-bikes.
Currently, many cities across the world are reallocating road space to pedestrians and cyclists to support social distancing, paving the way forward for enacting longer-term changes.
Other possibilities abound, including supporting people to work from home where possible, investing in transport powered by renewable energy and creating jobs that work towards a cleaner future.
“In other sectors,” Le Quéré suggests, “investments in building renovations create jobs and help reduce energy use in buildings. Planting trees and habitat restoration help enhance the carbon sinks and support the wood industry.
Natalie Parletta is a freelance science writer based in Adelaide and an adjunct senior research fellow with the University of South Australia.
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