May 27, 2021 | Alan Miller

IMT’s board members boast a plethora of accomplishments, and Alan Miller has added a new book on super climate pollutants to his credentials. In the book, Miller, an associate with Climate Finance Advisors and an adjunct professor at the Kogod School of Business at American University and the University of Maryland School of Public Policy, teamed up with co-authors Stephen Andersen and Durwood Zaelke to explain the importance of reducing four key pollutants as a means of rapidly slowing global warming. Miller recently spoke with IMT about the implications of these pollutants for buildings and the commercial real estate sector.

Can you explain what a super climate pollutant is and why they matter?

Super climate pollutants are technically called short-lived climate pollutants. We changed the name to more quickly and clearly communicate the power of these pollutants, and the opportunity to affect climate change now.

The core message of the book is that while carbon dioxide is the largest single contributor to global warming, it is very difficult to reduce it at the pace needed to avert the worst climate change consequences. The good news is that there is still a lot we can do to save what we can of our planet by accelerating strategies that slow warming the most in the near-term, starting with strategies that cut short-lived climate pollutants—hydrofluorocarbons (HFCs) used primarily as refrigerants and foam-blowing agents; black carbon (often called “soot”); methane (the primary component of natural gas); and tropospheric ozone (the bad kind of ozone at ground level, compared to the good ozone in the stratosphere that protects us from harmful ultraviolet radiation).

The short atmospheric lifetime of these “super pollutants” means that when we stop emitting them, they will fall out of the atmosphere much more quickly than carbon dioxide (CO2), and 90% of the warming they are causing will stop within a decade. For comparison, somewhere between 25 and 40% of CO2 stays in the atmosphere for 500 years or more causing warming. To avoid the most warming in the shortest amount of time we need to cut the super pollutants as quickly as possible, while also protecting the forests and other natural “sinks” that draw down and store CO2

In your book, you say that the four super climate pollutants cut across many sectors, including buildings, transportation, agriculture, and energy. Can you give examples of where these super climate pollutants show up in buildings? 

Two of the super climate pollutants commonly show up in buildings:  HFCs are embedded into most air conditioners and methane is released when natural gas is used for cooking and heating.

Air conditioning often uses HFCs as a refrigerant. These HFCs were originally introduced as a replacement for chlorofluorocarbons (CFCs), which were destroying the ozone. However, HFCs are nearly 12,000 times as powerful in terms of their warming potential compared to carbon dioxide. The Kigali Amendment to the Montreal Protocol addresses HFCs, and it is already spurring action. The U.S. Environmental Protection Agency, for example, is moving to take action and now China has announced it will ratify the amendment. Air conditioning manufacturers are supportive of reducing HFCs and will be incorporating solutions into new equipment. The issue is how to get rid of the existing air conditioners. People in hot climates are increasingly demanding air conditioning, at a rate that outstrips the capacity of renewable energy. This trend will continue as climate change continues to increase daily temperatures. People will want affordable air-conditioning machines, and that means they will likely purchase the cheapest models, which are often the least efficient. This means more CO2 will be burned to provide the energy needed to keep them on because renewable energy can’t keep up. Increasing efficiency is really the best way to deal with this.

Buildings often also use natural gas for heating and cooking and that gas is fundamentally methane. Over a 20-year time period it’s about 84 times as powerful a pollutant as CO2. In general, no one wants methane leaks because that represents wasted revenue for the producers or wasted expenses for the buyers. Additionally, methane has been connected to negative health outcomes, including to poor indoor air quality.

What are the main challenges to avoiding the use of super climate pollutants in buildings? 

The biggest challenges are really that so many existing buildings use air conditioners with HFCs and gas heating, making it logistically challenging and expensive to replace all those units. With air conditioning, we really need more efficient units at low prices to prevent additional CO2 emissions. To reduce methane, we need to get gas out of buildings as quickly as possible, and switch to electrified heat or ground-source (geothermal) heat pumps. Switching to electricity will have the most beneficial climate consequences if the relevant utility then switches the source of the electricity from fossil fuels (coal, oil, gas) to renewables.

What are the most promising solutions to eliminating super climate pollutants in buildings? 

In terms of air conditioning, there are a few approaches:

  • Bulk procurement is one solution. India’s government did a bulk procurement of efficient A/C systems as a way to reduce costs for these products.
  • Another solution is incentives, but they are tricky because it’s hard to do so equitably. You might end up subsidizing purchases of wealthier companies or individuals that can better navigate the bureaucratic processes involved.
  • Passive cooling is a promising solution that provides benefits regardless of what equipment is installed. Examples include planting trees or altering the roof to more effectively prevent heat transfer.
  • The best path is really to work with real estate and with manufacturers to develop joint solutions with support and expertise from all involved.

To reduce building-related methane, key solutions include:

  • Increase building efficiency
  • Switch from gas-powered to electrified HVAC systems and cooking appliances
  • Replace gas-powered heating systems with ground-source heat pumps. These are extremely efficient because they take advantage of the consistent temperature of the earth to produce heat.

In terms of reducing super climate pollutants more broadly, we need to focus on international collaboration, continue to invest in technological innovation, and to better utilize passive approaches to energy reduction. The international aspect is critical because many products are international. Air conditioners, for example, are largely produced in China. We need all new units to switch away from HFCs while retaining affordability. We also need to continue looking for technology solutions for everything ranging from building energy and heating to appliances and sensors. Lastly, we need to better use existing passive technology, like building shading and energy conservation, which is often relatively inexpensive and proven to lower energy use.  Our book, of course, provides more detail on what I’ve outlined here. Additionally, there is good data on Project Drawdown’s website that quantifies carbon savings from various solutions and delves deeper into building-related fixes.

How do we convince people to adopt these solutions?

It’s essential to help people, especially younger ones, see the importance of taking action. People who are buying properties and renting need to signal they care about efficiency and climate outcomes. We need clear market signals to facilitate a faster transition away from fossil fuels toward a more sustainable future.

Program Area(s):

International , Real Estate

Meet the Author

Alan Miller

Former IMT Board Member

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