COVID-19 and greenhouse gas emissions

The world saw striking images in the months of March and April 2020 as countries dealt with a pandemic. Some metropolitan areas experienced clear skies as shuttered factories and reduced transport eliminated the smoggy emissions that had previously fouled the air. During this unusual pause, many wondered what impacts this might have on greenhouse gas emissions.

The New Zealand experience

In a move to eliminate COVID-19 from the country, New Zealand closed its borders and confined people to their homes for 29 days during an Alert Level 4 lockdown. From 26 March to 27 April 2020, essential work continued and supermarkets stayed open, but schools, shops and workplaces closed. Those who could worked from home.

Scientists with the Ministry for the Environment wondered how this radical and sudden behaviour change affected emissions. They are also curious to know whether the changes resulting from this event can inform what changes in activity (and the forces driving emissions) may mean for emissions.

Changes in travel

During the lockdown, traffic in large urban areas dropped an average of 19–25% of 2019 levels. Heavy vehicles travelled up to 50–60% less compared to mid-March, but buses still ran to transport essential workers, sometimes with few or no passengers. Sea freight reduced, imports decreased by 21% and exports decreased by 17% in April compared to April 2019. Domestic air travel restrictions and the closed border decreased air traffic volume by about 80%.

Large reductions in air pollutants and emissions were observed. In Auckland, nitrogen dioxide levels decreased by 34–57%, and black carbon fell by 55–75%.

Globally, similar lockdowns cut carbon dioxide to 2006 levels. At its peak during the lockdowns in early April, daily carbon dioxide emissions were estimated to have decreased by 17% from 2019 levels. Reductions in road and air traffic made the biggest contributions.

Annual global emissions for 2020 are estimated to be down 4–7% on 2019 levels. Because annual global emissions are so large, a decrease of this size is unlikely to significantly affect the accumulation of carbon dioxide in the atmosphere unless this rate of decrease continues year on year for the next decades.

Short-term decreases during economic crises

The response to COVID-19 has come at an economic cost to New Zealand. Previous economic crises have caused emissions to decrease in the short term. For example, carbon emissions in America dropped by 26% during 1930–1932 due to the Great Depression. When the Soviet Union fell in 1991, its emissions also decreased.

Emissions levels rebounded except when the crises were driven by energy supply. Energy efficiency improved substantially, and alternative energy sources were developed as a result of the oil crises of the 1970s and 1980s. The current decreases to emissions are unlikely to be lasting unless structural changes are made to the world’s economic, transport or energy systems.

Normal activity and emissions resume

Transport and economic activity in New Zealand increased as restrictions on movement were eased in April and May. Normal activity resumed on 9 June 2020 (except for the border remaining closed). Traffic volumes returned to about 2019 levels 1 month later, being up to 94% in Auckland, 96% in Wellington and 100% in Dunedin. Christchurch and Hamilton exceeded 2019 traffic volumes by 4–5%.

The longest-lasting emission reductions are likely to be in tourism, which makes up about 7% of New Zealand’s greenhouse gas emissions (most of which is from air and land-based travel). However, reductions in international tourism may be partially offset by more domestic tourism as New Zealanders are encouraged to travel and support the recovery of local economies.

2021 – industry emissions still below pre-COVID 19 levels

StatsNZ reported that the New Zealand economy was still dealing with significant upheaval due to the pandemic. In the year ended September 2021, the country's businesses and households emitted 4.4% fewer greenhouse gases when compared with pre-COVID 2019 levels.