The climate-energy nexus

Key Concepts

  • CO2 emissions from human activity are by far the primary cause of climate change, and about 93% of these CO2 emissions are caused by burning fossil fuels. That points to three powerful means of mitigating the negative effects of climate change: (1) transition to lower- or non-carbon energy sources such as hydropower, wind, and solar; (2) capture more of the carbon released by fossil fuel combustion; and (3) reduce energy consumption through efficiencies.
  • The Paris Climate Accord, signed by the United States and 195 other parties in 2016, set an international goal to limit global temperature change to 2°C (3.6°F) above pre-industrial levels, to avoid the most drastic effects of climate change. Achieving that goal will require substantial reductions in carbon dioxide (CO2) emissions in the years ahead, given that an approximately 1°C increase has already occurred.
  • The sooner CO2 emission reductions are initiated and expanded, the longer the world will have before arriving at the 2°C limit—which means more time to implement adaptations (such as sea walls and higher-capacity storm sewers) and perhaps develop helpful technologies such as affordable methods for removing CO2 from the atmosphere. For example, if the world maintains its current rate of CO2 emissions, there is a 66% chance that the 2°C limit will be reached by 2044 (100% certainty is impossible to attain because of scientists’ incomplete understanding of how the many contributors to climate change interact). But if emissions reductions of just 4% annually were to start this year, it would take more than 100 years to reach that limit—essentially buying the world an extra 80 years to develop solutions.

A Few Facts to Know

  • U.S. annual CO2 emissions rose in 2018 after two years of declines; the independent federal Energy Information Administration has projected that U.S. energy-related CO2 emissions were “virtually flat” in 2019.
  • The United States is home to 4% of the world’s population but accounts for about 14% of global CO2 emissions.
  • CO2 is but one of several greenhouse gasses contributing to climate change. Methane, for example, is a far more potent greenhouse gas than CO2 although it has a shorter lifespan in the atmosphere.
  • The average U.S. resident consumes twice as much energy as the average E.U. resident, primarily because of Europe’s higher use of nuclear energy and hydro to produce its electricity.
  • Both wind and solar energy are now generally price competitive with fossil fuels for production of electricity, but these sources present challenges because their peak availability does not match peak demand (in winter, for example, peak energy demand is early morning and late evening, but peak sunlight for solar energy production occurs during midday), meaning the energy they produce must sometimes be stored for later use.
  • Burning natural gas to generate electricity produces about 60% less CO2 than using coal, making gas an imperfect but useful “bridge fuel” to help reduce CO2 emissions during a transition to renewables.
  • Renewable energy sources such as hydropower, solar, and wind cannot address the approximately 25% of global CO2 emissions that result from air travel, rail and ocean shipping, and certain industrial processes such as cement and steel making, which require extremely high temperatures, most easily achieved with fossil fuels. For those fossil fuel energy plants that must remain, carbon-capture technologies that absorb CO2 at the plant before it escapes to the atmosphere can significantly reduce greenhouse gas emissions.

SciLine generated this summary based on a presentation by Dr. Sally Benson, from Stanford University, on August 5, 2019, as part of our Science Essentials for Political Reporters boot camp. It is not intended to be comprehensive; it conveys the key points and major takeaways for reporters from Dr. Benson’s presentation.

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