The first half of 2020 has seen the largest-ever drop in carbon emissions in a single year, with bigger falls than the financial crisis of 2008, the 1979 oil crisis and even World War II.
“What makes our study unique is the analysis of meticulously collected near real-time data” said lead author Zhu Liu from Tsinghua University in Beijing.
“By looking at the daily figures compiled by the Carbon Monitor research initiative, we were able to get a much faster and more accurate overview, including timelines that show how emissions decreases have corresponded to lockdown measures in each country.
“In April, at the height of the first wave of corona infections, when most major countries shut down their public life and parts of their economy, emissions even declined by 16.9 per cent.
“Overall, the various outbreaks resulted in emission drops that we normally see only on a short-term basis on holidays such as Christmas or the Chinese Spring Festival.”
The greatest reduction of emissions was observed in the ground transportation sector, where working from home restrictions resulted in a 40 per cent drop in transport CO2 emissions worldwide.
In contrast, the power and industry sectors contributed less to the decline, with -22 per cent and -17 per cent respectively, as did the aviation and shipping sectors.
Surprisingly, even the residential sector saw a small emissions drop of 3 per cent: because of an abnormally warm winter in the northern hemisphere, heating energy consumption decreased with most people staying at home all day during lockdown periods.
The researchers based their estimates on a wide array of data: precise hourly datasets of electricity power production in 31 countries; daily vehicle traffic in more than 400 cities worldwide; daily global passenger flights; monthly production data for industry in 62 countries, as well as fuel consumption data for building emissions in more than 200 countries.
The researchers also found strong rebound effects. With the exception of a continuing decrease of emissions stemming from the transportation sector, by July 2020, as soon as lockdown measures were lifted most economies resumed their usual levels of emitting CO2.
Even if they remained at their historically low levels, this would have a rather minuscule effect on the long-term CO2 concentration in the atmosphere.
“While the CO2 drop is unprecedented, decreases of human activities cannot be the answer,” said Hans Joachim Schellnhuber, co-author and founding director of the Potsdam Institute for Climate Impact Research.
“Instead, we need structural and transformational changes in our energy production and consumption systems. Individual behaviour is certainly important, but what we really need to focus on is reducing the carbon intensity of our global economy.”