For the last 40 years, whenever the world economy grew, so did the Earth's carbon dioxide levels — until 2014, The Washington Post reports. The International Energy Agency (IEA) announced that in 2014, the economy grew and CO2 levels didn't.

In the past, a reduction in greenhouse gas emissions was due to an economic downturn. That's because economic growth is often linked to increased energy use, which in turn increases emissions. The "decoupling" of the economy and carbon emissions was likely the result of efforts by energy companies to fight climate change, the IEA says.

Last year, global carbon dioxide emissions reached 32.3 billion metric tons — an amount equal to 2013's levels. During the 40 years the IEA has been collecting data, there have only been three other periods of time when atmospheric CO2 levels did not rise: in the early 1980s, 1992, and 2009. However, these years were also associated with global economic instability, and in 2014, the global economy grew by 3 percent, according to the IEA.

"This gives me even more hope that humankind will be able to work together to combat climate change, the most important threat facing us today," IEA chief economist Fatih Birol said in a statement.

But atmospheric carbon dioxide levels are still high

The shift is due to China's increased use of renewable resources and efforts by countries in the Organization for Economic Co-operation and Development (OECD) to promote sustainable forms of energy, according to the IEA. Per-person energy use in the US is also expected to decline as the gross domestic product increases, The Washington Post reports.

This doesn't mean the fight against climate change is over. Carbon dioxide levels in the Earth's atmosphere reached record highs in 2013, and greenhouse gas continues to affect rapid and potentially disastrous climate change. Birol notes that the data provides "much-needed momentum to negotiators preparing to forge a global climate deal" at the United Nations Climate Change Conference in December.

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