People seeking to reduce their carbon footprint can choose from many sources of advice. One 2018 post by Columbia University’s Earth Institute offered 35 ideas – all well-researched and reasonable, but not clearly ranked, other than to note that air travel is likely the biggest contributor.

For the record, we at Impact Delta subscribe to the idea that every decision counts as the world seeks to chart a path to 45% lower emissions by 2030. Why 45%? This is the IPCC’s assessment of what is required to keep global warming below the 1.5 degrees Celsius threshold, nicely summarized by The Guardian here.  Meanwhile, the media firm Quartz has taken the “every decision” concept and turned it into a tagline for its coverage of climate change, for example here.

But the debate, for reasons which may not be totally innocent, is only recently moving to a prioritization of actions individuals can take. Part of the problem is most people don’t know what their carbon footprint is, nor where it comes from. A December 2019 national poll by the Washington Post and the Kaiser Family Foundation produced some conflicting results. It found rising levels concern about climate change. But it also found relatively low levels of climate-related knowledge. For example:

  • Two out of five adults, and nearly three out of five teens, thought plastic bags were a major contributor to climate change;
  • More than one in three thought “the sun getting hotter” was a major contributor; and
  • Only 24% thought airplane travel was a major contributor.

These findings prompt some further questions:

  • First, what are the facts? What do we know about which actions lower emissions the most? Are individuals more able to adjust some aspects of their carbon footprint than others?
  • Second, what are the investment implications? Specifically, will there be demand for more education? And as the public becomes more educated, what longer-term investable themes can we identify?

High-impact carbon reduction

We won’t go through all 35 ideas discussed by the Earth Institute. But there is a lot of ground to cover, and so we’ll split it up over a series of posts.

We’ll take a look at the five biggest areas of energy use to see how they compare. The punchline? Air travel is the area most consumers should review, if they seek to shrink their footprint quickly. But there’s nuance to this too.

The category-by-category exploration blends some personal experience with U.S. national level data. It also tests out some of the arithmetic that goes into standard estimates of carbon footprints in the U.S.

Consistent with most research on the topic, our five categories are:

  1. Residential energy use
  2. Travel (we focus on car and aircraft travel)
  3. Food
  4. Goods
  5. Services

In the next post, we’ll dig into the first, residential energy use.