Carbon dioxide emissions are up again—and increased coal use is the main culprit.

That’s the key takeaway from a report released last week by the International Energy Agency, which found that global energy-related CO2 emissions rose by 6% in 2021 to 36.3 billion tons.

It’s the highest-ever level, as the world rebounded from the Covid-19 crisis and relied more heavily on coal to power that growth, the IEA said. The fossil fuel accounted for more than 40% of the overall growth in global CO2 emissions last year, reaching an all-time high of 15.3 billion tons.

The chart above shows the pandemic-induced CO2 emissions decline in 2020, the strong rebound in 2021 and the net annual change.

The biggest increase in CO2 emissions by sector was in electricity and heat production, which represented 46% of the global increase. China accounted for almost all the global increase in this sector between 2019 and 2021.

Overall, the CO2 emissions increase in the power and heat sector was driven by the biggest ever year-on-year increase in global electricity demand, which stood at 5.9%, the IEA said. This was more than 15 times the size of the drop in demand in 2020.

But there’s good news here as well. Despite the rebound in coal use, renewable energy sources and nuclear power provided a higher share of global electricity generation than coal in 2021.

Transport was the only sector in which global CO2 emissions remained well below 2019 levels, the IEA said. However, the emissions reduction impact of record electric car sales in 2021 was cancelled out by the parallel increase in the sales of SUVs.

These numbers show that the world has not recovered sustainably from the pandemic.

“The world must now ensure that the global rebound in emissions in 2021 was a one-off—and that an accelerated energy transition contributes to global energy security and lower energy prices for consumers,” the IEA said.