The national debate about climate change has reached a crucial point. We have had eight years of modest progress in reducing greenhouse gas emissions. The best known and most controversial part of that effort is the Clean Power Plan, which is intended to reduce greenhouse gas emissions from fossil fueled power plants. The new Trump Administration is bent on scrapping the Clean Power Plan and, it appears, much of the rest of the national greenhouse gas reduction effort.
The politics of this issue obscure the massive challenge ahead of us. Starting now, we must rapidly engage in “deep decarbonization”—reducing greenhouse gas emissions to zero or below by the second half of this century. For the U.S., this requires a reduction of at least 80% by 2050. (Reducing greenhouse gas emissions to zero by 2050 would be even better.) To put this in perspective, U.S. greenhouse gas emissions in 2014 were nine percent below those of a decade earlier (2005). But achieving deep decarbonization will require the U.S. to reduce its greenhouse gas emissions by at least five percent every year.
A recently developed concept—the carbon budget—provides a way of understanding both the magnitude of this challenge and possible pathways for an effective response. In the 2015 Paris Agreement on Climate Change, nations of the world agreed that keeping atmospheric greenhouse gas levels below dangerous levels requires keeping the temperatures “well below” 2 degrees Celsius (or 3.6 degrees Fahrenheit) above preindustrial levels.
Scientists have translated these limits on temperature increases into carbon “budgets”—numerical limitations on additional emissions. To have a two-in-three chance of keeping the global temperature increase below 2 degrees Celsius, the U.N. Environmental Program says in a 2016 report, global greenhouse gas emissions must fall from 52.7 gigatons of carbon dioxide equivalent in 2014 to 23 gigatons in 2050, and -3 gigatons in 2100. (A gigatons is one billion tons).
Three sets of decarbonization reports have been prepared for the United States. The Deep Decarbonization Pathways Project (DDPP), which is led by Sustainable Development Solutions Network and the Institute for Sustainable Development and International Relations, has prepared both a technical report and a policy report. In November 2016, the U.S. government issued a deep decarbonization strategy for 2050, entitled U.S. Mid-Century Strategy for Deep Decarbonization. (It was posted on the White House website but was removed from that site shortly after Trump’s inauguration.) Late last year, the Risky Business Project, which was founded by former New York City Mayor Michael Bloomberg, former U.S. Secretary of the Treasury Hank Paulson, and businessman and philanthropist Tom Steyer, issued its own decarbonization strategy for the U.S., entitled From Risk to Return, Investing in a Clean Energy Economy.
The two DDPP reports for the U.S. provide a sense of the changes required to actually achieve deep decarbonization. Because it is difficult to decarbonize gas and liquid fuels, the researchers said, meeting the 2050 objective would require almost complete decarbonization of electricity. Among other things, that would require switching a “large share” of end uses that require gasoline and liquid fuels over to electricity (such as electric cars). It would also be necessary to produce fuel from electricity itself, they said, citing the production of hydrogen from hydrolysis as an example.
These changes would double electricity generation but reduce its carbon intensity (carbon emissions per dollar of GDP) to 3 to 10 percent of current levels. Achieving that result would require not only great increases in energy efficiency but a vast increase in either renewable energy (as much as “2,500 gigawatts (GW) of wind and solar generation (30 times present capacity))” or carbon capture and sequestration. The average fuel economy for light duty vehicles such as cars would need to be over 100 miles per gallon, and these vehicles would need to be fueled almost entirely by electricity and hydrogen.
The overall cost of this effort would be roughly one percent of GDP, the researchers say. But it would bring considerable economic, security, job creation, public health, and environmental benefits—apart from the avoided costs of climate change.
A next step is figuring out the legal pathways to achieve these reductions at the federal, state, and local level. These legal pathways also include forms of private law and governance, including supply chain contracts. Professor Michael Gerrard of Columbia University Law School and I are editing a book on this topic that should be published later this year.
From the chapters we have edited thus far, it is clear that there are a variety of legal approaches to deep decarbonization. The loss of the Clean Power Plan would not set back a U.S. decarbonization effort if it were replaced with equivalent or more effective measures.
There is no time to lose. We are already about half way to the 2 degree Celsius limit. According to a January 18 NASA report, global surface temperatures in 2016 reached their highest level ever, 1.78 degrees Fahrenheit (0.99 degrees Celsius) warmer than the mid-20th century average. The federal effort must be strengthened, not weakened. And whatever the federal government does or does not do, states, localities, and businesses must step up their efforts to decarbonize.