How to limit global warming to less than 1.5 degrees Celsius

Many climate scientists and policymakers believe that the 2015 Paris Agreement’s goal of limiting global warming to less than 1.5 degrees Celsius (2.7 degrees Fahrenheit) is unattainable. This is not surprising given that the global average temperature is already 1.2 degrees Celsius above pre-industrial levels. Climate modelers project that it will rise to about 1.5 degrees Celsius by 2030, 2 degrees Celsius by 2050, and 2.5 to 3 degrees Celsius by 2100.

Instead of accepting this defeatist attitude, the United States should lead a global “moonshot” program to limit global warming to less than 1.5 degrees Celsius.

The U.S. Inflation Reduction Act (IRA) of 2022 is a good start in reducing America’s greenhouse gas emissions. However, it is not nearly enough to limit global warming to less than 1.5 degrees Celsius. This bill provides about $370 billion in subsidies and $250 billion in loan guarantees over the next decade to promote:

• Clean technologies and industries, including solar, wind and nuclear power generation
• Energy storage, energy efficiency and electric vehicles
• Building insulation and electrification
• Hydrogen and ammonia production
• Forest management and agricultural practices to enhance nature-based carbon removal
• Carbon capture and sequestration
• Energy breakthrough research and development

In addition to these investments, the bill includes a hefty methane-emissions fee to influence oil and gas companies to eliminate most methane emissions.

While the IRA is a significant step forward, two additional policies are needed to limit global warming to less than 1.5 degrees Celsius:

Carbon pricing: First and most importantly, the U.S. must price carbon and other greenhouse gases at their social cost — and encourage all other countries to do the same. This will create a robust global market for clean, renewable and efficient energy technologies as well as carbon removal and sequestration processes.

Carbon can be priced in three ways: 1) carbon taxes 2) emissions trading and 3) carbon fees and dividends. About one-quarter of the world’s countries currently price carbon using one or more of these methods. Unfortunately, in most countries, the carbon price is too low to reduce emissions significantly.

Every country should price carbon at its social cost. The carbon price should start low to prevent excessive economic disruption (for example, less than $50 per ton of carbon dioxide) and increase over time to reflect its actual social cost (perhaps $200 per ton in 2022 dollars). To be most effective, the carbon price should apply to all greenhouse gas emissions, not just carbon dioxide, and the credit should be given for carbon removed from the atmosphere.

Carbon pricing has several significant side benefits. For example, in addition to decreasing greenhouse gas emissions, it will 1) reduce air pollution 2) decrease dependence on oil, natural gas and coal, 3) promote sustainable forestry and farming practices and 4) improve land-use policies and decisions.

The wealthiest households will pay most of the cost of addressing climate change if carbon is priced using a carbon fee and dividend program, as proposed by leading economists, the bipartisan Citizens’ Climate Lobby, and the Republican Climate Leadership Council. This is fair because 1) the wealthiest households are responsible for a disproportionate share of greenhouse gas emissions, and 2) they can afford the (small) incremental cost of addressing climate change.

Solar geoengineering: Second, the U.S. should initiate and lead a global research program to develop solar geoengineering technology to mitigate global warming. The National Academies of Science, Engineering, and Medicine proposed such a program in their report, “Reflecting Sunlight: Recommendations for Solar Geoengineering Research and Research Governance.”

The goal of this program should be to develop at least one geoengineering technology by 2030 to limit global warming to less than 1.5 degrees Celsius. The United Nations could then decide whether to use this technology in 2030 or succeeding years.

The most-studied method of solar geoengineering is the injection of sulfur into the stratosphere at an altitude of about 20 kilometers (12 miles). Volcanoes currently inject sulfur into the atmosphere at various locations and heights. This lowers global and regional temperatures. In the case of solar geoengineering, the location, altitude, timing and quantity of the injections would be selected to reduce global and regional temperatures while minimizing potentially harmful side effects.

Solar geoengineering should only be used after all viable emissions reduction strategies have been implemented. Modeling with EN-ROADS, a computer model developed by MIT and Climate Interactive, suggests that carbon pricing can limit global warming to about 2 degrees Celsius in 2100, after which carbon removal exceeds emissions. A pragmatic, incremental solar geoengineering program should be able to offset one-quarter of this temperature increase (0.5 degrees Celsius) and limit global warming to less than 1.5 degrees Celsius with acceptable risk and a cost of less than $5 billion annually. An example program is defined in “Stratospheric Aerosol Injection Tactics and Costs in the First 15 Years of Deployment,” published in Environmental Research Letters in2018.

If the world continues today’s incremental, scatter-shot approach to address climate change, global warming will almost certainly exceed 1.5 degrees Celsius of warming in less than 10 years. However, who could have imagined in 1957, when the Soviet Union launched the Sputnik satellite, that the U.S. would land astronauts on the moon and return them safely in 1969? Now, an international “moonshot” program can cost-effectively limit global warming to less than 1.5 degrees Celsius. This will encourage clean, sustainable economic growth and provide an improved foundation for global prosperity and peace.

The U.S. should lead this endeavor and invite China, the European Union, and other countries to participate and co-lead this effort. This will challenge and revitalize America — and the world — just as the space race did in the 1960s.

Jim Hartung recently retired from Pratt and Whitney Rocketdyne after a 40-year career in aerospace and energy. He helped develop the International Space Station as the director of systems engineering and integration for its Electric Power System. He led the development of many clean and renewable energy technologies as director of energy systems for Pratt and Whitney Rocketdyne. Hartung is also the author of “Rational Tax Reform: Using the Systems Engineering Process to Fix America’s Broken Tax System,” Which illustrates how systems engineering can address complex social, economic and political problems. He is a member of the International Council on Systems Engineering (INCOSE) and the Citizens’ Climate Lobby (CCL). The ideas presented in this op-ed are the author’s own.