The U.S. was the world’s biggest carbon polluter until it was overtaken by China in the mid-2000s. However, despite cutting emissions in recent decades, the U.S remains by far the biggest emitter in history. Cumulatively, fossil fuel combustion in the U.S. has released more than 400 GtCO₂ since the Industrial Revolution began in the 1750s. Due to the sheer volume of planet warming gases it has released into the atmosphere throughout its history, many critics and observers believe the country bears the most responsibility for climate change.
What are the largest sources of U.S. emissions?Greenhouse gases are emitted by a variety of sources in the U.S., with some far more polluting than others. Transportation generates the largest share of GHG emissions in the U.S. at around 29 percent, followed by the electric power sector, at 25 percent. The latter was previously the largest producer of CO₂ in the U.S., but a shift away from coal-fired power to natural gas and renewable energy sources has reduced emissions of CO₂ in this sector by 36 percent since 2005. Meanwhile, CO₂ emissions from transportation have been on an upward trend, and although they plummeted in 2020 because of COVID-19, they have since rebounded and totaled 1.8 GtCO₂ in 2022.
U.S. climate targetsFollowing the election of Joe Biden in 2020, his administration vouched to prioritize climate action. In addition to rejoining the Paris Agreement, the Biden Administration committed the U.S. to a net-zero future by 2050 at the latest. During the 26th United Nations Climate Change Conference (COP26) in 2021, the U.S. also signed-up to the Global Methane Pledge, to slash methane emissions by 30 percent by 2030.
Additionally, the United States' Nationally Determined Contribution (NDC) was strengthened in 2021 by setting a new and ambitious climate target of cutting emissions by 50 to 52 percent below 2005 levels by 2030. This new target is significantly higher than the previous pledge of cutting emissions by 26 to 28 percent by 2025. However, while this target is deemed achievable, it is projected that additional policies will need to be implemented for it to be met. The U.S.’s pathway to net-zero includes the deployment of new technologies such as renewable energy sources and sustainable fuels, as well as improving energy efficiency across economic sectors.