The world cut its daily carbon dioxide emissions by 17%, or 17 million tonnes, in April when the pandemic-induced lockdown was at its peak, a new study found on Tuesday. But with life and heat-trapping gas levels inching back towards normal, the brief pollution break will likely be “a drop in the ocean” when it comes to climate change, scientists said.

The study, published in the British journal Nature Climate Change, said India cut its carbon emissions by 26% in April. For a week in April, the United States cut its carbon dioxide levels by about one-third or 30.7%. China, the world’s biggest emitter of heat-trapping gases, sliced its carbon pollution by nearly a quarter, that is by 23.9%, in February.

The international team of scientists calculated that although the pollution levels are heading back up, the world could be on the course of recording a 4% to 7% drop in emissions by the end of 2020. It will be 7% if the strictest lockdown restrictions remain all year long across much of the globe, and 4% if they are lifted soon. “That figure would mark the largest annual decrease in carbon emissions since World War II,” the study added.

But the scientists warned that the decrease in emissions this year will not do much to impact overall climate change, as it is “extremely small” compared to the emissions accumulated so far, and compared to the emissions cuts needed to tackle climate change. The study cited the United Nations Environment Programme, which states that a decrease of 2.7% per year of greenhouse gases are needed to global keep warming well below 2 degrees Celsius and 7.6% per year to keep below the temperature below 1.5 degrees Celsius.

Furthermore, most changes observed in 2020 are likely to be temporary, as they do not reflect structural changes in the economic, transport or energy systems, the study added. “The change for the rest of the year will depend on the duration and extent of the confinement, the time it will take to resume normal activities and the degree to which life will resume its pre-confinement course,” it said.

The authors recommended that decision-makers should focus on policies around transport and mobility, given that it contributed to nearly half the decrease in emissions during confinement. “Emissions from land transport accounted for almost half – 43% – of the decrease, while power generation accounted for 19%, industry for 25% and aviation for 10%,” it said.

Scientists warned that the rush for economic stimulus packages must not make future emissions higher by delaying new green deals or weakening emissions standards. “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.”