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What it would take for U.S. to meet its Paris commitment

Posted on 20 June 2022 by dana1981

This is a re-post from Yale Climate Connections

The Biden administration in April 2021 dramatically ratcheted up the country’s greenhouse gas emissions reductions pledge under the Paris target, also known as its Nationally Determined Contribution (NDC).

The Obama administration in 2014 had announced a commitment to cut U.S. emissions 26-28% below 2005 levels by 2025. The Trump administration formally withdrew the country from the Paris agreement in late 2020, but the Biden administration, upon taking office in January 2021, swiftly reversed that move and subsequently pledged to cut U.S. emissions 50-52% below 2005 levels by 2030.

Based on current emissions trends and climate policies, however, the U.S. is not on track to meet even the Obama administration’s commitment, let alone its new and far more ambitious NDC. With two-thirds of the time between 2005 and 2030 having passed, national emissions today are only about 15% lower than the 2005 levels. In fact, carbon pollution rates had been rising during the Trump administration’s tenure until the COVID pandemic struck.

With eight years remaining before the looming 2030 deadline, authors of a new study in the journal Science examine how seven energy system model scenarios envision the U.S.’s ramping up efforts to meet its NDC. In short, achieving its commitment would require efforts to dramatically accelerate the deployment of solar panels, wind turbines, electric vehicles (EVs), trees, heat pumps, insulation, and measures to significantly curb the emissions of other potent greenhouse gases like methane.

What it would take to meet the Biden pledge

The U.S. released 6.6 billion tons (gigatons, or Gt) of carbon dioxide (CO2)-equivalent greenhouse gases in 2005, about 5.6 Gt in pre-pandemic 2019, and has pledged not to exceed 3.3 Gt of emissions in 2030. That objective means the U.S. needs to reduce its annual emissions a further 2.3 Gt in the next eight years. The Science study incorporated the results of seven separate energy system modeling scenarios that tried to project how the U.S. could achieve that goal:

  • A scenario designed and directed by the Environmental Defense Fund using the Rhodium Group’s version of the U.S. Energy Information Administration’s National Energy Modeling System (NEMS);
  • An analysis by the University of Maryland Center for Global Sustainability, World Resources Institute, and Rocky Mountain Institute using the Joint Global Change Research Institute’s Global Change Analysis model (GCAM);
  • A scenario from the Lawrence Berkeley National Laboratory using its own model in collaboration with models from the National Renewable Energy Laboratory (NREL) and Energy Exemplar;
  • An analysis by the Natural Resources Defense Council using a model developed by Evolved Energy Research;
  • A scenario by the Electric Power Research Institute using its own model; and
  • Two analyses by the Massachusetts Institute of Technology using its own model integrated with one from NREL.

Consistency among model scenarios

The various model scenarios were fairly consistent in projecting that close to half of the needed reduction – about 1.1 Gt – should come from the electricity sector. That effort would require installing an average of about 60 gigawatts (GW) of combined solar and wind energy per year from now through 2030. For comparison, about 33 GW of wind and solar were installed in the U.S. in both 2020 and again in 2021. That’s approximately double the amount of national renewable energy installations in 2015, and the rate would need to approximately double again on average over the subsequent eight years to put the U.S. on track to meet its Paris commitment. At the same time, 90 to 100% of American coal power plants would need to retire by 2030.

The models were similarly aggressive in projecting the contribution to the needed emissions cuts from transportation, estimating that this sector would have to reduce its annual greenhouse gases by about 600 million tons (Mt) by 2030 (nearly a quarter of the total emissions cuts needed). More than 80% of U.S. transportation sector emissions come from road transport – cars, SUVs, pickup trucks, buses, and heavy-duty trucks – all of which could be electrified. Switching to EVs would dramatically reduce transportation emissions, especially as the electric grid continues to decarbonize.

Reaching the models’ target would require that EV popularity grow from 4% of U.S. annual new car sales today to 34 to 100% (the model average was 67%) in eight years. Based on current policies, EVs are projected to reach around 35 to 40% of new car sales in 2030, and the Biden administration has set a target of boosting that figure to 50%.

EV deployment chartAnnual EV share of new car sales in the U.S. through 2021 (yellow) and in the growth required in the seven model scenarios to meet the 2030 national NDC. Source: Bistline et al. (2022), Science.

The models were consistent in finding that the next-largest emissions cut would likely need to come from potent greenhouse gases like methane and hydrofluorocarbons (HFCs, which are primarily used for cooling in refrigeration and air conditioning units). Those emissions would need to decrease by around 460 Mt of CO2-equivalent by 2030, representing 18% of the reductions required to meet the NDC.

Land sinks would need to sequester about 200 Mt more CO2 in 2030 than they do today (about 8% of the total cuts needed). Nearly all annual natural carbon sequestration in the U.S. currently comes from tree growth in forests and urban settings. Other approaches to achieve more permanent carbon dioxide removal are being developed, but in the near-term, reforestation and afforestation are the most promising ways to boost American natural carbon sequestration.

Finally, emission reductions from building electrification (primarily transitioning from fossil fuel heating to electric heat pumps) and efficiency (e.g., improving insulation) would need to amount to about 125 Mt per year by 2030 to meet the U.S. NDC, according to the average of the model scenarios. Those cuts would represent about 5% of the overall emissions reductions needed.

Average projected contributionProportion of emissions cuts needed in each sector by 2030 to meet U.S. NDC, according to the average of model scenarios. Created by Dana Nuccitelli based on data from Bistline et al. (2022), Science.

U.S. Paris commitment technically achievable … with a big BUT

All of the individual sectoral goals outlined above are technically achievable. But based on current policies, energy systems models agree that U.S. emissions will decline only modestly between now and 2030, likely falling at least halfway short of its NDC.

The deployment of solar panels, wind turbines, and EVs could be accelerated through the expansion of existing tax credits such as those included in the House’s Build Back Better legislation last November, but since stalemated in the U.S. Senate. Senator Joe Manchin (D-WV)  has been negotiating with Senate Majority Leader Chuck Schumer, which could potentially lead to passage of the tax credit expansions sometime this summer.

On the question of potent greenhouse gases, the Environmental Protection Agency is expected to soon adopt stricter methane regulations for the oil and gas industry, and Manchin says he remains open to the possibility of including a methane pollution fee in a budget reconciliation package. The Senate Foreign Relations Committee also recently advanced to the Senate floor the international Kigali Amendment, which would phase out HFCs.

The amount of carbon sequestered by U.S. lands has remained steady over the past 15 years, but the bipartisan Infrastructure Investment and Jobs Act signed into law last year included reforestation legislation that could help boost that number. Recent studies from the National Academy of Sciences and published in Science Advances and Global Change Biology conclude that by maximizing its land sinks, the U.S. potentially could increase its annual natural CO2 sequestration by about 1 Gt. The bipartisan infrastructure package also included $3.5 billion for the Weatherization Assistance Program to help low-income households weatherize their homes. That funding could help weatherize about 500,000 homes – a good start, but only a fraction of a percent of all homes in the U.S.

In short, America’s NDC remains within reach, but meeting it would require substantial efforts to accelerate the deployment of solar panels, wind turbines, EVs, trees, heat pumps, and insulation, and for the oil and gas industry to reign in its methane leakage problem. Without additional legislative efforts like the tax credits being negotiated by Manchin and Schumer, the U.S. will fall well short of its 2030 climate commitment.

As the latest report from the Intergovernmental Panel on Climate Change concluded, the Paris targets remain technically within reach, but political will remains a substantial roadblock in their path.

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