eia-2017年美国与能源有关的二氧化碳排放量（英文）-2018.10-22页

U.S. Energy-Related Carbon Dioxide Emissions, 2017 Summary

Core Content

The U.S. energy-related carbon dioxide (CO2) emissions decreased by 0.9% in 2017, reaching 5,142 million metric tons (MMmt), down from 5,189 MMmt in 2016. This decline occurred despite a 2.3% increase in real GDP, indicating that the reduction in emissions was driven by factors other than economic growth. These factors included a decline in carbon intensity of the energy supply, a drop in energy intensity, and a decrease in the overall carbon intensity of the economy.

Main Points

Overall Emissions Trend

• Total emissions: 5,142 MMmt in 2017, a 47 MMmt decrease from 2016.
• Annual GDP growth: 2.3% from 2016 to 2017.
• Emissions decline since 2005: 14% below 2005 levels, representing an 849 MMmt reduction.
• 2017 emissions growth above trend: 20 MMmt higher than the 2006–2016 trend due to more robust economic growth.

Fuel Contributions

• Coal emissions: Continued decline since the recession, though still more carbon-intensive than natural gas.
• Natural gas emissions: Declined by 1.5% in 2017, surpassing coal emissions in 2015. Its increasing share in electricity generation helped reduce the carbon intensity of the energy supply.
• Petroleum and other liquids: Emissions have been increasing since 2012 after a period of stability and decline.
• Non-carbon sources: Wind and solar electricity generation contributed significantly to the decline in carbon intensity.

End-Use Sectors

• Transportation sector: The only end-use sector with an increase in CO2 emissions, up by 16 MMmt (0.8%).
  • Jet and diesel fuel: Led the increase, with jet fuel contributing 58% of the total transportation emissions growth.
  • Motor gasoline: Declined by 0.3% due to higher prices.
• Commercial sector: Emissions decreased by 19 MMmt (2.1%).
  • Indirect emissions: Declined by 3.5% due to lower electricity use and reduced carbon intensity.
  • Direct emissions: Increased by 1.7%.
• Residential sector: Emissions fell to the lowest level since the late 1980s, down by 26 MMmt (2.6%).
  • Seasonal variation: First-quarter emissions were unusually low due to reduced heating demand.
  • Energy efficiency: Improved lighting efficiency contributed to lower emissions.
• Industrial sector: Emissions declined by 1.3% (18 MMmt), driven by less energy-intensive production and increased natural gas use.

Electricity Generation

• Carbon intensity decline: The shift from coal to natural gas and growth in non-carbon sources (wind, solar) reduced the carbon intensity of electricity generation.
• Coal share: Declined from 52% in 1990 to 30% in 2017.
• Natural gas share: Increased from ~12% in 1990 to 32% in 2017.
• Non-carbon generation: Exceeded coal and natural gas in 2016 and 2017, with wind and solar contributing 22% of non-carbon generation in 2017.

Key Information

• Economic factors: GDP per capita growth (1.5%) and population growth (0.7%) contributed to higher emissions than the 2006–2016 trend.
• Carbon intensity: Declined by 1.1% in 2017, consistent with the 2006–2016 average.
• Energy intensity: Fell by 2.0%, faster than the 2006–2016 average of 1.5%, leading to a 27 MMmt reduction in emissions.
• Sectoral changes:
  • Transportation: Emissions increased due to higher jet and diesel use, offset by lower motor gasoline emissions.
  • Commercial and residential sectors: Indirect emissions from electricity use declined significantly, while direct emissions increased slightly.
  • Industrial sector: Emissions decreased due to a shift toward less carbon-intensive fuels and production methods.

Future Implications

• The 2017 decline in CO2 emissions does not necessarily indicate future trends.
• EIA forecasts and projections are available in the Short-Term Energy Outlook (STEO) and Annual Energy Outlook (AEO), which provide insights into emissions and their drivers up to 2050.
• The International Energy Outlook (IEO) also contains projections for global energy consumption and emissions.

Terms and Methodology

• British thermal unit (Btu): A unit of energy used to measure heat.
• Carbon intensity (economy): CO2 emissions per unit of GDP (CO2/GDP).
• Carbon intensity (energy supply): CO2 emissions per unit of energy consumed (CO2/Btu).
• Cooling degree days (CDD): Used to measure air conditioning energy demand.
• Heating degree days (HDD): Used to measure heating energy demand.
• Energy intensity: Energy consumed per unit of economic output (Btu/GDP).
• Kaya Identity: A framework used to decompose CO2 emissions into factors such as GDP, population, energy intensity, and carbon intensity of the energy supply.

Tables Summary

• Table 1: Shows the weighted changes in electricity and primary energy consumption by sector, along with their impact on CO2 emissions.
• Table 2: Provides CO2 emissions from electricity generation in the commercial and industrial sectors for the years 2005 to 2017.

Conclusion

The 2017 U.S. energy-related CO2 emissions were influenced by a combination of economic growth, fuel mix changes, and energy efficiency improvements. While emissions declined overall, the transportation sector remained a growing source of CO2, and the shift toward natural gas and non-carbon energy sources played a key role in reducing the carbon intensity of electricity generation. These trends highlight the complex interplay between economic activity, energy consumption, and environmental impact.