Net Greenhouse Gas Emissions
Net greenhouse gas emissions (carbon dioxide, methane, nitrous oxide, fluorinated gases), including discharge from land use and deforestation.
Why did we include this measure?
Greenhouse gases trap the sun’s rays and cause the earth to warm, resulting in several predictable environmental effects. The number of extreme heat days increases, causing dehydration, exhaustion, and heat strokes and making us less healthy and productive. Warming also increases extreme weather events. The rising number and severity of droughts and floods make it difficult to grow crops, while the increasing severity of hurricanes, superstorms, and wildfires destroys homes and businesses and sometimes costs lives. Climate change is a concern in part because a large share of the nation’s—and the world’s—population lives near large bodies of water. Climate change is melting glaciers, raising sea levels, and likely increasing the severity of hurricanes, all of which particularly affect coastal areas.
How does the US rank globally?
- Specific Measure: (Same as above.)
(Source: Authors’ analysis of Climate Watch data).
- Percentage of countries the US outperforms: 1% (out of 114 countries)
- International Rank Trend: Stable
National Trend Mixed
What do the data show?
The United States is the second-highest annual emitter of greenhouse gases after China. Our trends are mixed because our emissions were rising into the mid-2000s and that trend has subsequently reversed, so that our emissions are still almost identical to 1990. We are still easily the highest cumulative emitter since the Industrial Revolution.
What might explain these patterns?
Greenhouse gas emissions are driven heavily by economic activity, which is currently dependent on energy consumption and the burning of fossil fuels. It is no coincidence that China and the US are the top two countries ranked by economy size and emissions. We are generating economic output more efficiently than in the past—with lower greenhouse gas emissions per unit of output—but the overall problem is getting worse because these gases accumulate in the atmosphere.
The primary greenhouse gas is carbon dioxide, which is responsible for 80% of gross US greenhouse gas emissions. The main sources are transportation, electricity generation, and industry. We have improved in these areas in recent years by switching from coal to natural gas, expanding the use of renewable energy, and improving efficiency in all of the major sources, especially vehicles. Methane represents only 12% of US greenhouse gas emissions but has particularly large warming effects. Methane comes mainly from animal agriculture, oil and gas industry operations, and landfills.
For more information about data sources and treatments, download the Data Notes.