The global lockdown that was in place for much of April led to a 17 per cent fall in daily carbon emissions, according to the first peer-reviewed study on the impact of the coronavirus crisis on emissions levels.

The study, which was published this afternoon in the journal Nature Climate Change, calculates that daily emissions fell by 17 million tonnes of carbon dioxide during the peak of the confinement measures in early April when compared to mean daily levels seen in 2019. Overall, the lockdown is estimated to have led to fall in global emissions back to a level last observed in 2006.

The analysis confirms the dramatic reduction in emissions was driven largely by a sharp fall in transport, energy, and industrial emissions.

Emissions from surface transport, such as car journeys, accounted for almost half of the decrease in global emissions during the peak confinement day on April 7. Similarly, emissions from industry and power together accounted for a further 43 per cent of the decrease in daily global emissions, while 10 per cent of the fall was driven by the massive contraction in the number of flights from the global aviation industry.

The lower levels of carbon emissions were only marginally offset by an increase in energy use that resulted from millions of people working from home.

The paper highlights how even with drastic changes to behaviour, emissions savings remain far short of the level required to deliver net zero emissions by mid-century.

"Population confinement has led to drastic changes in energy use and CO2 emissions," said Prof Corinne Le Quéré of the University of East Anglia, who led the analysis. "These extreme decreases are likely to be temporary though, as they do not reflect structural changes in the economic, transport, or energy systems."

She added that as such the extent to which world leaders consider climate change when planning their economic responses post COVID-19 "will influence the global CO2 emissions paths for decades to come".

"Opportunities exist to make real, durable, changes and be more resilient to future crises, by implementing economic stimulus packages that also help meet climate targets, especially for mobility, which accounts for half the decrease in emissions during confinement," she said. "For example in cities and suburbs, supporting walking and cycling, and the uptake of electric bikes, is far cheaper and better for wellbeing and air quality than building roads, and it preserves social distancing."

With many countries now easing lockdown restrictions, the report estimates the impact of confinement on 2020 annual emissions will lead to a reduction of around four to seven per cent compared to 2019 levels, depending on the duration of the lockdown and the extent of the recovery. If pre-pandemic conditions of mobility and economic activity return by mid-June, the overall decline would be around four per cent globally, the paper calculated. But if some restrictions remain worldwide until the end of the year, it could result in a fall of around seven per cent.

A seven per cent cut in emissions is comparable to the amount of annual emission reductions needed year-on-year across decades to achieve the climate objectives of the UN Paris Agreement, the report authors noted.

"The drop in emissions is substantial but illustrates the challenge of reaching our Paris climate commitments," said Prof Rob Jackson of Stanford University and Chair of the Global Carbon Project who co- authored the analysis. "We need systemic change through green energy and electric cars, not temporary reductions from enforced behaviour."

The call for systemic change is the latest in an increasingly vocal campaign for governments to prioritise climate action as part of their economic recovery plans. In the past 24 hours alone, a coalition of over 150 corporates and a separate group of over 200 state leaders have added their voices to the chorus of calls for a green recovery.