Global carbon dioxide emissions could fall by up to 7% this year, depending on ongoing restrictions and social distancing measures during the coronavirus pandemic, research published in the journal Nature Climate Change showed on Tuesday.

The study, by a group of scientists from institutions in Europe, the United States and Australia, analysed daily CO2 emissions across 69 countries, 50 U.S. states, 30 Chinese provinces, six economic sectors, and three levels of confinement, using data from daily electricity use and mobility tracking services.


In 2019, the world emitted around 100 million tonnes of carbon dioxide per day by burning fossil fuels and cement production, the research said.


In early April 2020, emissions fell to 83 million tonnes per day, a drop of 17%, and some countries’ emissions dropped by as much as 26% on average during the peak of the confinement.


If pre-pandemic conditions return by mid-June, then 2020 emissions could decline by 4% compared to 2019 but if restrictions remain worldwide until the end of the year, then emissions could drop by 7%, the report added.


This would be the largest single annual decrease in absolute emissions since the end of World War II.


A U.N. report last year said emissions needed to drop by 2.7% a year keep warming well below 2 degrees Celsius, and 7.6% a year to keep below 1.5C.


“Population confinement has led to drastic changes in energy use and CO2 emissions,” said lead author Corinne Le Quéré at the University of East Anglia.


“These extreme decreases are likely to be temporary, however, as they do not reflect structural changes in the economic, transport, or energy systems,” she added.


China saw the largest drop in emissions in April, followed by the United States, Europe and India.


In the countries with the strictest lockdown restrictions, emissions from aviation plunged 75% in early April, while emissions from land transport fell by 50% and from power generation by 15%.Emissions from industry declined by around 35%, with a lack of data causing some uncertainty. Emissions from residential buildings, however, increased by 5%, the study said.


“The emissions reductions occurring because of COVID-19 will clearly be unprecedented. What is less certain is how the economy will rebound in late 2020 and 2021,” said Glen Peters at the CICERO Center for International Climate Research in Norway, which took part in the study.


“As different countries and sectors recover, it is unclear if activity levels will return to normal levels or if we may see permanent shifts in behaviour,” he added.