How has staying home affected global CO2 emissions?

In order to prevent further spread of COVID-19, governments around the world closed borders and confined people to their homes. These measures reduced transportation and changed energy consumption habits. Le Quéré et al. found that global CO2 emissions decreased by 17% from April 2019 to April 2020.

As of May 28, some countries have started to ease their restrictions, while others are still in lockdown. What happens with the spread and intensity of the coronavirus in the coming months will help determine how governments and the public choose to act. The team behind the Nature paper estimates that overall 2020 emissions will be around 4% lower if pre-pandemic conditions return by June 2020 and around 7% lower if some restrictions remain worldwide until the end of the year.

Based on the data used in the Nature paper, which looked at emissions from the beginning of 2020 through April, the day when CO2 pollution dropped the most was April 7. The one sector with the greatest drop was land transport, which accounted for more than 40% of the decrease.

A working paper done in collaboration between university scientists and the National Bureau of Economic Research found that around 46 million metric tons less of CO2 were emitted per month, a 19% decline. This reduction is attributed to social distancing.

While the first cases of COVID-19 in the United States go as far back as January 2020, it was on March 11 when President Donald Trump addressed the nation about the pandemic and shut down a significant amount of international travel. Soon after, states began to order lockdowns. Overall, the United States has experienced an overall emissions drop of 32% this year due in large part to these shutdowns and travel stoppages.

China was the first country to experience the novel coronavirus; although at first the government tried to cover up the problem, eventually it shut down much of the country surrounding Wuhan, the worst-hit area. Since the beginning of 2020, the country’s overall emissions have dropped by 24%. The country has already begun reopening.

China’s Hubei province is home to the city of Wuhan, where the COVID-19 outbreak is believed to have started. It experienced the earliest and most restrictive lockdown in the country. Reduced movement, consumption, and manufacturing caused the province to experience a drop in CO2 emissions of 27%.

Italy was the first European country to experience a surge in COVID-19 cases, leading the country to begin quarantining different areas in February 2020. The majority of the country’s cases were in the north, where much of the nation’s business and manufacturing takes place. Eventually, all nonessential production was shut down along with travel and all other businesses, and emissions in the country dropped by 28% between January and April.

California’s CO2 emissions dropped by 41.8%—more than any other state in the United States—with 50% of this reduction coming from transportation and 19% from industry. California was the first state to enact sweeping lockdowns.

New York saw its emissions go down by 33%, with 41% of this reduction coming from transportation and 20% from residential reductions. New York state has been the hardest hit in terms of coronavirus cases and deaths, and New York City's economy will remain closed until at least mid-June.

Across the globe, CO2 emissions decreased by 7% due to reduced power use through April. This power includes both residential and public/commercial use electricity, as well as heat production, and it accounts for 44.3% of global CO2 emissions.

Across Europe, the demand for electricity decreased overall. This is unsurprising as manufacturing shut down, and stores and offices closed beginning in February or March, depending on the country. The data from the Nature paper for Europe was collected through April 17.

Electricity use dropped in the United States by 6% in March and April for similar reasons as Europe during the same time period. The Edison Electric Institute, which is an industry lobby group, indicated that during the week of April 18, the demand for power in the United States hit a 17-year low.

Every state experienced a decrease in demand for electricity except for two—California and Florida. High temperatures requiring air conditioning, coupled with the fact that the state never totally shut down, accounts for this discrepancy in Florida.

Emissions from industry, which includes production of material such as steel, manufacturing, and cement, dropped by 19% worldwide during the period included in Nature's data. According to the paper, the reduction in CO2 emissions comes primarily from changes in China's coal consumption. These industry emissions represent 22.4% of global CO2 emissions.

Another factor in emission drops from industry is that American steel production has decreased since mid-March, when automakers temporarily halted production in order to limit the spread of COVID-19. Plants began reopening in late May, although the Chicago Assembly Plant on the city’s far south side had to close twice in two days because workers showed up sick.

The beginning of the COVID-19 crisis in China happened right around the time of the Chinese New Year, which is also a time of low industrial production. The Lunar New Year, combined with the road blockades and lockdowns due to the pandemic, caused a decline of 6% in the first two months of the year. As of Feb. 14, only 57% of China’s coal mines were functional. However, the production is expected to recover for the rest of the year with a forecasted decline of only 1.2% by the end of the year.

Due to less commercial transport as well as fewer people driving to their offices or taking their cars on vacation, global emissions from cars and trucks have decreased by 36% as compared with 2019. This has contributed to an overall global CO2 emissions decrease of 43%. However, scientists fear that as restrictions are lifted, car use will spike with people remaining wary of public transportation.

Across six continents, excluding Antarctica, mobility of people has decreased. This mobility doesn’t just include car, plane, train, and bus transport, but also movement by bicycle or foot. In the United States, this is due in large part to lockdown measures, which have kept people at home, and places with stronger measures have less mobility.

Because fewer cars, trucks, and buses are on the road, cities around the world are experiencing much lower levels of traffic congestion. In Mumbai, India, once lockdown measures took effect, average traffic congestion went down 60% in March compared to the 2019 average.

Due to lockdown measures, road traffic decreased in the United Kingdom, which naturally affects CO2 emissions. By the end of March, road travel levels were lower than any year since 1955.

The United States has also experienced a reduction in car traffic caused by COVID-19 lockdown measures. A March mapping study by Smart Cities Dive found that due to reduced traffic congestion caused by lockdowns, travel time into the core of Chicago sped up by 77% and into Los Angeles by 53%.

As many cities and states went into lockdown due to the COVID-19 pandemic, personal travel in the United States dropped by 40%. However, as the summer vacation season approaches, it is possible that people will resume travel but will opt for road trips instead of the air.

As borders shut down and air traffic decreased, CO2 emissions from flying dropped by 60% when comparing April 7, 2020 to the same time in 2019. This has contributed to 10% of the total global CO2 decrease. In an average year, aviation accounts for around 2.8% of total CO2 emissions. However, flying also emits nitrogen oxides, water vapor, and particulates that have additional warming impacts.

As governments tried to limit the spread of the novel coronavirus, countries closed their borders and many flights were canceled. For example, on Jan. 23, 20,000 flights landed in or departed from Europe. However, Italy soon became a COVID-19 epicenter and travel restrictions took hold in Europe. By March 23, flights to and from Europe dropped to fewer than 5,000 per day.

Half of all flights were canceled once stay-at-home orders went into effect in the United States. Although as of May 28, more flights are being scheduled and taken, there are still far fewer air travelers than last year. On May 22, 348,673 people had been screened by the Transportation Security Administration across the United States. Last year at the same time, more than 2.7 million people had been screened.

Germany’s airline Lufthansa cut its long-haul flights by 90% starting in mid-March and ran only 20% of its flights within Europe. Austrian Airlines, a subsidiary of Lufthansa, halted all its flights at that time except to repatriate Austrians stuck abroad.

Outdoor air pollution causes an estimated 4.2 million deaths each year, according to the World Health Organization. The reduced CO2 emissions are expected to avert 25% of premature deaths caused by air pollution this year. Already in Europe, scientists estimate that 11,000 fewer people have died because of the cleaner air.

A working paper from the National Bureau of Economic Research found that the environmental benefit from social distancing will add up to $5.5 billion per month. Nearly 60% of this economic benefit comes from reduced deaths resulting from lower emissions.

A Harvard study from April found that counties in the United States with higher amounts of particle pollution are linked to higher COVID-19 death rates. Hopefully the reduction in CO2 emissions due to lockdown will help lower the death rate in these at-risk communities, and everyone will be able to maintain lower emissions once social distancing restrictions are eased.