The South American giant emitted 9.4 billion metric tonnes of greenhouse gases during Bolsonaro's four years in power (2019-2022), breaking the nine billion mark for the first time since 2003-2006, the Climate Observatory, a Brazilian coalition of environmental groups, said in its annual emissions report.

In 2022, Brazil's emissions fell by eight percent, to 2.3 billion tonnes, but that was still the third-highest level since 2005, surpassed only by 2019 and 2021, also under Bolsonaro.

The report attributed much of the fall in 2022 to heavy rains that enabled the country to rely on its vast network of hydroelectric dams for power.

With Brazil, like much of the world, hit by a recent series of environmental disasters, the group said the figures are a wake-up call on the urgency of limiting global warming to 1.5 degrees Celsius, the target of the Paris climate accord.

"The catastrophic extremes of 2023 have shown the world what life looks like above 1.5 degrees. No one wants that," Marcio Astrini, the Climate Observatory's executive secretary, said in a statement.

The emissions figure makes Brazil the world's sixth-biggest greenhouse gas polluter, after China, the United States, India, Russia and Indonesia, it said.

If the European Union is counted as a single unit, Brazil falls to seventh.

The report found that the lion's share of Brazil's emissions last year -- 48 percent -- came from deforestation, especially in the Amazon rainforest, a vital resource against climate change.

The agriculture sector came second, at 27 percent.

Deforestation in the Brazilian Amazon rose sharply under Bolsonaro, an agribusiness ally who pushed to develop the rainforest for farming and mining.

President Luiz Inacio Lula da Silva, who took office in January, has vowed to end illegal deforestation by 2030.

With the next round of UN climate talks opening next week, Brazil has room to slash its emissions by far more than it has pledged under the Paris deal (to 1.2 billion tonnes by 2030), the study's authors said.

"If this government is serious when it says it defends the Paris accord... it will have to increase its ambition for 2030, like all the biggest emitters," said David Tsai, the study's coordinator.