Annual Greenhouse Gas Emissions

Carbon dioxide is the main gas heating the planet. Six others—more powerful than CO2 but much less abundant—absorb heat as well. They are expressed below as equivalents to CO2.
Photographs: Luke Sharrett, Daniel Acker, Adam Berry, Munshi Ahmed, Andrew Harrer, Chris Ratcliffe / Bloomberg News
Source: Rhodium Group

Why this number

There was a time, about three centuries ago, when human civilization released no significant amount of greenhouse gases. That changed with the start of the Industrial Revolution and large-scale coal-burning to power steam engines. Along the way, humanity discovered new resources and engineered new chemicals that, along with CO2, make up the catalog of gases that trap heat in the atmosphere.

Inside the metric

CO2 is responsible for about three-quarters of global warming. Given this dominant role, scientists simplify things by rendering all other heat-trapping gases into terms of carbon-dioxide equivalent, or CO2e, when tracking cumulative emissions. Each of the other gases has a “global warming potential,” or a measure of how much heat it absorbs, expressed in relation to CO2, and CO2 itself has a global warming potential of 1. Added up, we get worldwide total CO2e of all greenhouse gases released each year.

The other six greenhouse gases are much more powerful than CO2 in a molecule-for-molecule comparison, but are released in lower amounts or leave the atmosphere more quickly. Atmospheric CO2 lingers for hundreds or thousands of years. Methane is 25 times more potent than CO2 over a century, the timespan over which estimates are calculated. Sulfur hexafluoride, a chemical used in the power sector, is 22,800 times stronger than CO2.

How we know

The Rhodium Group, which provided data to Bloomberg Green, estimates CO2-equivalent annually by analyzing sector- and country-level economic data.

The six other greenhouse gases are responsible for about 25% of the planet’s rising temperature. The second-most prevalent, methane, accounts for almost 17% of the global total and has been rising significantly since 2007. The most common human sources of methane are farming and livestock—cows are notoriously prolific methane producers, in the form of belching—and the energy industry. The top natural sources include wetlands, lakes, geologic seeps and termite colonies. What worries scientists is the potential for warming itself to cause enormous new leaks of methane. In particular, melting arctic permafrost could release large amounts.

Agriculture is also the main source of nitrous oxide, which accounts for 6% of total emissions, mostly from fertilizer. It’s also emitted from vehicles, power plants and manure. The rest, about 2%, are called “F-gases” because they contain the element fluorine. These chemicals are used in refrigerators, air conditioning and power-transmission equipment. Some are by-products of aluminum production and semiconductor manufacturing.

What progress looks like

In principle, the goal is simple: Roll this number downward by phasing-out emissions until reaching zero. In practice, however, this number continues to rise. Global CO2 emissions from fossil fuels stopped growing from 2014-2016, suggesting that the level may be close to peaking. Increases resumed since then, despite a temporary drop-off during 2020 pandemic quarantines. These emissions need to fall to half their 2010 level by 2030 to keep alive the Paris Agreement goal of limiting warming to below 1.5°C.

There’s some help on the way. Dozens of countries, including nine of the 10 largest economies have pledged to zero-out emissions by mid-century. Ground and satellite monitoring is exposing the world’s most-concerning sources of methane, with awareness rising both inside and outside industry. No collective task has ever been more difficult.