The global pandemic unleashed in China and now spreading around the world is paralyzing economies, as factories shut down, banks close, and people isolate to contain the outbreak.

The effects are clear. China’s GDP might have dropped 40% during the first three months of the year, while the US’ GDP could fall by 30% to 50% by summer. Similar trends are seen in all countries, with annual output expected to decline across the globe.

But countries’ GDP isn’t the only figure expected to drop this year. Reduced economic activity has a direct effect on the level of greenhouse gas emissions, now expected to decline up to 4% in 2020, according to an analysis by CarbonBrief – based on data that represents three-quarters of global emissions.

Such an annual drop would be larger than any previous economic recession or war managed to bring about, according to Simon Evans, the deputy editor at CarbonBrief. But it still underscores just how massive and challenging a job the world faces in cutting emissions fast and deep enough to combat climate change.

The Paris Agreement, signed in 2015, seeks to limit global warming to 1.5ºC compared to pre-industrial levels. To reach that goal, the world would have to cut emissions by 6% every year for the next decade, according to CarbonBrief. That means that shutting down the economy this year won’t be enough to solve the problem.

At the same time, emissions are also likely to rebound as soon as economies get back on track, which is what happened in the wake of previous downturns. Indeed, China’s are already about within the normal range, a few months after the outbreak crested in some provinces.

Data from countries and sectors not yet available is expected to increase the total drop of emissions, CarbonBrief explained, also noting that some estimates of oil consumption declines have grown since they completed their post. They also cautioned that efforts to gauge the virus’s effects are complicated by unknowns regarding the duration of the crisis and lockdowns, among other variables.

The report provides a sense of the staggering effects of the outbreak that’s freezing huge amounts of travel and economic activity. But it also gives an unfolding, real-time look at the immense challenge implementing policies to meet the goals of the Paris climate agreement.

With the current country’s pledges, the global temperature increase is expected to reach 4ºC, instead of the 1.5ºC agreed on in Paris. New climate plans are expected by all countries this year — with Chile as the most recent example weeks ago — in order to increase ambition further.