Which personal action has the strongest impact on reducing the CO2 footprint of an average American or German? Turns out this question is surprisingly difficult to answer for most of us. And what are the next best five or ten things we should do to cut CO2? There is surprisingly little guidance out there. Because of that, I fear that we may not manage to cut emissions as much as we have to. That's why Carsten and I did the legwork for you!

I have to admit that Greta got to me. Perhaps because I also have a daughter some consider to be on the spectrum as well (remember Greta's hate speech at the UN?..."how dare you"...we get this regularly when we ask our daughter to lay the table). So what does a management consultant do if he wants to take personal action on CO2? Look for a concise, quantitative, prioritized list of key drivers that he can select from (since CO2 footprints differ by country, we looked for German information). Obviously, there is a ton of information out there, but it is usually in one of the following categories:

The "Everything-under-the-sun" list gives you too many items and does not prioritize even though the effects may differ by an order of magnitude. The "Energy saver" list has useful personal actions but focuses only on one aspect of your life, usually heating and/or electricity. The Calculator enables you to really get to the bottom of your very own personal profile and simulate in great detail what effect individual actions would have. Classic German over-engineering that only a tiny group of zealots will ever use. The "Kill-yourself-and-your-family" list is very close to what we had in mind, but lists as most important driver "Have one fewer child". Seriously?! This is as factually correct as saying that if you kill yourself right now, you will achieve the biggest possible CO2 saving. Needless to say, including this lever in the infographic is a very dumb idea because it creates a backlash and destroys good intentions.

But thanks to all these lists and useful calculators, we were able to come up with the following overview quickly. It is still work-in-progress, not perfect at all, and sometimes we have conflicting data points, but hey, it's a start.

We have grouped the actions into

what we can actually start doing today - in other words, actions that don't take too much effort, like fuel-efficient driving

what takes more planning and preparation, like reducing the number of flights you take or switching to green electricity

what may take considerable investments, like switching to modern heating and insulating your home better.

As a vegetarian household with top-notch heating and insulation, with an electric car, green electricity, and no daily car commute, I can check off many actions on that list. However, there are some drivers that were new to me, like washing clothes in cold water. The good news is that if I implement all these levers, I will achieve about 75% of the reduction target defined by the government for 2030! How cool is that?!

And now comes the bad news.

We asked 1500 Americans and 1500 Germans to select from a list of seven personal actions the one that has the strongest impact on reducing the CO2 footprint of an average person. (Addition Nov. 7, 2019: The phrasing of the question was as follows: „Which of the following personal actions has the strongest impact on reducing the CO2 footprint of an average American?“ The sample was 1500 randomly selected respondents. The sample error was 3.3% (RSME score) and subsequently automatically weighted to ensure that the sample is representative for the overall population of people aged 18+ that use the internet (>95%, depending on the country). The ranking of the actions did not change before/after the weighting, it is pretty robust.)

Here comes the list:

Energy-efficient heating/cooling/insulation

Avoid one return trip by aircraft per year

Eat less red meat

Fuel-efficient driving

Buy local and seasonal produce

Unplug unused electronics to stop standby

No more plastic bags

We presented the list to respondents in a randomized order, but the list above is in descending order of impact. For example, in Germany, the impact of energy-efficient heating & insulation on our CO2 footprint is a whopping 250 times bigger than stopping to use plastic bags.

Guess which action was selected most often in Germany? "No more plastic bags"! Seriously?!

Here is the drama in all its gory details:

We were hoping that this is due to Germany's unique obsession with recycling trash since the 1980s. But "no more plastic bags" actually made it to number 2 on the list in the US as well, very close behind fuel-efficient driving. Here is the comparison between both countries:

It is difficult to say who is more clueless, because both countries have their specific blind spots: That "one flight less per year" comes out so low in the US is just as ridiculous as the fact that meat consumption is not really seen as a source of CO2 in Germany.

I wish I had taken the survey myself before doing the math on the actual drivers. I am certain I had my fair share of ignorance! For example, I grossly overestimated the effect of having no daily commute to work. But we are not here to poke and pry, but rather to drive action! So now that I know all the numbers, I have pledged to substantially reduce my flights.

Epilogue (Nov. 7, 2019): Our survey results made national headlines in the past few days (the biggest newspaper, most prestigious magazine, most prestigious newspaper in Germany):

While I felt flattered by the media attention, it was disheartening to see that the press only focused on people’s knowledge gap. In all fairness, that was the hook to this story as well, but we used this hook to sell you our graph of the most important personal levers to reduce CO2.

Addendum (Nov. 12, 2019) - Methodology Synopsis: If you have made it this far down in the article, I congratulate you! Perhaps then you still have some more patience for the intricacies of the research design. Since there have been some questions and also pure disbelief at the survey results, please let me add a bit of color to the surveys we did. Perhaps that will help you decide whether "people aren't clueless, they are lazy and maybe a bit self-indulgent", as Lloyd puts it on www.treehugger.com.

In a nutshell: my interpretation of the data at hand is that the majority of the effect is driven by lack of knowledge . Here is why:

To find out what really is the issue, we asked the same concept (personal CO2 levers) slightly differently three times to get to the truth (monadic survey design, i.e., each survey was shown to a different group of respondents, but each sample was representative for the overall population):

1) Question for factual knowledge (biggest lever) - aided, with a list of seven items to choose from. This type of question is easiest to understand and to answer, respondents just need to select one item from a list. No behavioral intention is asked which could distort respondents' judgment.

2) Question for behavioral intention of their friends - aided, with a list of six items to choose from (the results were published in our second article). This question is more difficult to answer and more likely to be distorted by what may be socially desirable. That's why we did not ask for that they themselves would do, but what they think their friends will do.

3) Question for factual knowledge (biggest lever) - unaided, i.e., open question, without any hint. This question is most difficult to answer from a knowledge perspective. (We have not published the results of this survey so far, because we felt the intricacies of the differences between those surveys are for experts only, like you ;-)

Here are the results:

"No plastic bags" topped the list both in survey 1 and 2, albeit with a significant difference in %, as you would expect. That difference is exactly the effect of "virtue signaling" and "laziness" when it comes to behavioral intentions. But it is still number 1 without those (22% "no plastic bags" in 1 vs. 55% in 2).

In survey 3, with the open, unaided format, about 40% of respondents did not give any meaningful answer. So they either did not know or were unwilling to answer. Not good. 47% mentioned anything around cars and alternative modes of transportation, which thus tops the list of actions. Only 15% thought air traffic is the biggest driver, closely followed by changing meat consumption (14%). 8% consider reducing plastic consumption is most effective (No. 4). Only then comes modern heating (just 4%!).

I think the picture that is emerging is pretty clear and consistent: While laziness and virtue signaling are very important drivers, it is a lack of knowledge that remains a key issue.

Here is another piece of corroborating evidence: Through dark channels, our key graph ended up on Reddit's most important German forum r/de and generated more than 4000 likes and 500 comments within 12 hours. The survey results were so surprising to some Reddit users that some of them actually re-ran our survey on their own, albeit with a smaller sample size and through a panel, but still with a few hundred respondents. You can find the results here and here. In essence, their results were consistent with ours .

Erratum (Nov. 8, 2019): Our original estimate for going vegetarian (-780 kg CO2 per year) was based on this government website run by co2online. Their source is the German Environment Agency and their CO2 calculator which we also used heavily. When we tried to reproduce the -780 kg using that calculator we found the following: -780 kg can only be achieved when one not only goes vegetarian, but also buys exclusively regional, seasonal, and organic produce and never uses frozen foods as well! Since our analysis of drivers is meant to be ceteris paribus, we decided to change it to -450 kg for "no more meat" only.