Climate 411

For the U.S. to do its part to help avoid the worst impacts of climate change, we must achieve a 100% clean economy by 2050 at the latest – removing at least as much climate pollution from the atmosphere as we put into it each year. (Read this for more on what we mean by “100% clean” or why this should be the goal.)  But what does a 100% clean economy actually look like and how do we get there?

Several studies have examined how the U.S. can cut emissions 80% from 2005 levels by 2050, such as the Obama Administration’s Mid-Century Strategy for Deep Decarbonization. More recently, Evolved Energy’s 350 ppm Pathways for the United States became the first major report to identify pathways for the U.S. to achieve even deeper reductions: net-zero carbon dioxide (CO­₂) emissions by 2050.

A 100% clean economy by 2050 is ambitious but necessary. To achieve it, we’ll need policies that drive down  climate pollution and substantial acceleration of clean energy innovation. Deep decarbonization studies suggest that with comprehensive climate policy and technology progress as a foundation, a 100% clean economy will most likely rely on:

• Rapidly transitioning to a clean electricity system. We already have a good idea of how to clean up the electricity sector. Several zero-carbon sources (wind, solar, hydro, nuclear) have been widely deployed and are already among the most cost-effective options for new generation. As a result, the electricity sector is likely to transition quicker and more cost effectively than any other part of the economy.
• Electrifying as much as possible. Electrifying major sectors like transportation and buildings cuts fossil fuel use and reduces emissions even with today’s electricity mix. It will lead to even greater reductions as electricity gets cleaner.
• Deploying low carbon fuels where electrification isn’t practical. Cleaner alternatives to fossil fuels, including hydrogen, synthetic gas, and biofuels can fill in where electrification is tricky, such as for high temperature heat needed for manufacturing processes and in aviation.
• Advancing energy efficiency. Energy efficiency lowers the amount of energy required—and therefore the emissions produced. Today, there are cost-effective energy efficiency opportunities in every sector of the economy, from vehicles to appliances to industrial equipment. As technology improves, even more opportunities to save energy while saving money will become available.
• Removing carbon dioxide from the atmosphere. Protecting and increasing natural carbon “sinks” like forests or by deploying technologies that suck CO₂ directly out of the air can help lower concentrations of carbon dioxide in the atmosphere, helping us reach 100% clean as quickly as possible. Also, because it will be very challenging to completely eliminate emissions from all parts of the economy, especially industry and transportation, carbon dioxide removal (CDR) can help ensure we’re taking as much carbon out of the atmosphere as we’re putting into it. There is disagreement over how big the potential carbon sink is from natural sources (the Evolved study, for instance, assumes the potential for natural CDR is large relative to other estimates). To the extent less natural CDR is available, we will need more technological CDR or more carbon mitigation.
• Reducing non-CO₂ CO₂ is the dominant climate pollutant responsible for climate change, but there are other major greenhouse gases that trap more heat on a per ton basis, such as methane, nitrous oxide and hydrofluorocarbons (HFCs). These gases are emitted not only through energy consumption but as byproducts of a wide variety of activities such as agriculture, oil and gas industries, landfills, and refrigeration and air conditioning. There are various strategies available to reduce these greenhouse gas emissions, but some sources are easier to reduce than others. For example, cutting edge techniques to limit methane emissions from livestock can only reduce emissions by 30%, even as livestock-related emissions are likely to grow as the population grows. More RD&D, incentives, regulations and technical assistance across the economy will be needed to reduce these emissions and deploy available technologies.

This suite of strategies, some of which are already cost-competitive with more polluting alternatives, could take off with a pollution limit in place. The chart below, based on Evolved Energy’s data, shows how these strategies might intersect to help the U.S. reach a 100% clean economy (although it’s important to note that the Evolved analysis only considered energy-related CO­₂ emissions).

(Click to Enlarge) *With electrification, there will be less direct use of fossil fuel, but the fuels that remain will tend to be more energy and carbon intensive **Includes negative emissions from biomass, increased sequestration in natural sinks, and negative emissions technologies +Some of the savings attributed to EE could also be attributed to electrification, as many electric technologies use less energy to provide the same service compared to fossil fuel burning alternatives

The contributions of each of the strategies in the figure should be considered rough orders of magnitude rather than precise estimates. There are many different ways to project the potential emissions reductions from each strategy, and each strategy also interacts and influences the others. For example, the extent to which expanded electrification leads to emissions reductions depends heavily on how clean the electricity sector becomes. The important thing to note is that we will have to make dramatic progress in each of these areas in order to achieve a 100% clean economy.

We can also see that even as overall emissions decline, there are forces pushing some sources of emissions up: Historically, as economic growth increased, so did energy consumption and emissions. While there’s recent evidence this relationship may be growing weaker, in general, higher GDP is associated with more energy demand. And while we expect to electrify a lot of the economy, not all equipment can be easily electrified, especially those that require the most energy, like airplanes and some industrial processes that require extremely high temperatures. As a result, the remaining fuels that are not replaced with electricity are more carbon intensive than the average of all of the fuels used today. So while there’s less direct use of fossil fuels, what’s left may be more carbon intensive.

At the big picture level, a 100% clean economy will be vastly more efficient, more reliant on clean electricity, and will deploy technologies and practices that capture and store at least as many emissions as we produce. Let’s go deeper and explore how a 100% clean economy might transform specific sectors:

• In commercial and residential buildings, much of the energy needed for space and water heating and cooking will come from electricity. This will require next-generation appliance standards, more ambitious building codes, and incentives to adopt efficient electric technologies like electric heat pumps. Maximizing energy efficiency in new buildings will be essential: many of the buildings built today will still be standing in 2050.
• Increased electrification will also be necessary in the industrial sector, although many industrial processes will be hard to electrify. Fuel switching to alternative low- or no-carbon sources like hydrogen or sustainable biofuels, as well as energy and material efficiency – making less resource-intensive products – can also significantly reduce industrial sector emissions. Finally, many industrial processes are good candidates for carbon capture and storage technologies that capture carbon emissions to be stored underground or put to productive use.
• Electrification and efficiency will drive a lot of the transportation sector emission reductions. The Evolved analysis assumes that electric vehicles and other zero carbon alternatives like fuel cells make up nearly 100% of new vehicle sales by the end of the 2030s, up from only a few percent today. This will require expanded incentives for electric vehicles coupled with stronger climate pollution standards for cars and trucks (like the ones the Trump Administration is trying to roll back).

Deep decarbonization studies also often rely on biofuels as a large source of transportation emissions reductions, although measuring the full emissions footprint of biofuels is challenging and controversial.  What we do know is that, for applications such as jet fuel, electrification is unlikely, and therefore deployment of verifiably sustainable biofuels could play an important role in getting to 100% clean.

Taken together, transitioning to a 100% clean economy by midcentury will require an unprecedented transformation of our economy. Understanding the core elements of a 100% clean economy can help us design policies to accelerate the needed transition to a more efficient economy that relies more heavily on clean electricity and low carbon fuels, and which reduces as much climate pollution as it produces.

The good news is there are signs of progress. Several pieces of federal climate legislation have been introduced by members of both parties that would begin to put us on the right path. While a 100% clean economy ultimately requires that Congress enact legislation to drive down climate pollution, innovation is also an important piece of the climate puzzle, and it currently enjoys bipartisan support in Congress. And states across the country are already taking action.

100% clean is 100% achievable: now we need to build the political will to make it a reality.