Green nudges, clever and not so clever

Behavioural science can do its bit in averting severe climate change, but it has to be done well

How will climate change affect you personally? This can be hard to tell. There is broad scientific consensus that it is happening (and will continue to happen). Sophisticated models project numerous consequences, from increasingly extreme weather patterns to dramatic rises in sea level. But it is not easy to imagine, let alone determine, how precisely all this will affect your own life.

Perhaps the migration of certain species might pay a role for you. If, like the author, you are keen on brown shrimp, you might be alarmed by the findings of a recent report (in Dutch) on the Seawatch-b initiative by the Flemish Institute for the Sea. It suggests that, as a result of the rising temperature of the North Sea water (+1.7 degree C, twice as fast as the global average), the prevalence of these delicious creatures has fallen by 80% since the beginning of this century.

It’s hard to see how forest fires and the advancing sea would have much effect of us when we live in a large city nowhere near large woodlands, way inland. For many people climate change will be a matter of many small effects (like rarer and more expensive shrimp).

Likewise, it is hard to see how a few, massive interventions (like spraying minuscule reflective particles into the stratosphere to block sunlight) could counteract climate change. Just like an investment across a broad portfolio of assets is a better bet for a comfortable retirement than putting all your savings in Apple, Alphabet or Amazon stock, many more modest interventions are going to be needed to slow down climate change. We will all need to make small changes to our behaviour, especially regarding the numerous ways in which we consume energy. How can we do that?

One study from a few years back, conducted by three economists, Greer Gosnell, John List and Robert Metcalfe, showed how airline pilots could be encouraged to reduce fuel consumption. Pilots make numerous decisions, and some of those significantly affect kerosene consumption. Before the flight they need to establish how much fuel should be pumped into the aeroplane: taking more fuel than necessary will increase consumption (as the plane needs to carry the weight of the excess fuel). When they’ve landed and taxi to the stand, they can choose to do so on just one engine and switch off the others, which will save fuel. And of course, during the flight, they can adjust their speed and altitude, both of which influence momentaneous consumption.

The researchers divided 335 Virgin Atlantic captains across 40,000 flights in four groups. One group received monthly performance feedback, including the percentage of their flights during which they exhibited the three types of fuel-saving behaviour (before, during and after the flight). The second group got the same report, plus a personalized performance target 25 percentage points above their baseline performance prior to the experiment. Captains in the third group received the same feedback and targets as their colleagues in the second group, but as an extra incentive, for each target they achieved, the company would donate £10 to a charity of the pilot’s choice. The final group was a control, in which the participants received no information, targets or incentives. Pilots of the other three groups received the information by post to their home address every month for eight months, the duration of the experiment.

Captains in all groups (including the control!) significantly changed their behaviour, but the best result was found in the groups that received performance targets. (The incentive of a charitable donation made no difference to the behaviour, but these pilots reported higher job satisfaction.) Overall, throughout the experiment, an estimated reduction in CO2 emissions of 21,500 tonnes, and a cost saving of $5.4 million, representing just over 0.5% of total consumption. (If you think this does not sound all that spectacular, remember two things: this was easily achieved at negligible cost, and combating climate change is a matter of numerous small interventions, not a few huge ones.)

Little box, big effect (source)

Consumers too can be nudged to reduce their energy consumption, and there have been many trials and studies exploring the opportunities over the last ten years. One of the first ones (started in 2009) introduced the Home Energy Report. This was developed in conjunction with Robert Cialdini, a veteran behavioural scientist, and provides households with two key types of information: the actual consumption, with tips on how to reduce it, and a comparison of their consumption pattern with their neighbours’. 3 years on, this low-tech intervention helped participants typically save between 2 and 4% on their previous energy bills.

Another, more recent, example is a field experiment involving about 150 households on the Dutch island of Texel, conducted in 2014 by Erdal Aydin, and economist at the Turkish university of Sabanci and colleagues. It used an in-home display to provide much more immediate feedback to the consumers, and quickly achieved (and sustained) a reduction in consumption of around 20%.

Why were these interventions, both with the airline captains and with the households as consumers of energy, successful? One factor was a clear behavioural starting point. To change people’s behaviour, you need three things: an understanding of what they do right now, a clear definition of what they ought to be doing, and a clear-cut mechanism by which they are more likely to choose the desired behaviour over the old one. For example, refuelling, taxiing and adjusting speed and altitude were identified as crucial decision points where old and new behaviour were positioned. Likewise, there are discrete, well-defined things consumers can do to cut down their energy usage, from replacing incandescent bulbs with low-power ones, to showering for the duration of The Ramones’ Blitzkrieg Bop (2:12) rather than prog rockers Genesis’ Supper’s Ready (22:54). Reminding people of such actions, and providing encouragement (by showing them similar consumers that actually do better) gently nudges people towards greener behaviour.

But not all interventions are so well-thought through.

The environmental footprint of the Flemish (the Dutch-speaking Belgians) is considerably higher than that of citizens in the neighbouring countries, and a study (in Dutch) commissioned by the Flemish regional government identified two main reasons. One is the elevated energy consumption, the other is the high mileage people drive — because key amenities like shops, schools, public transport links, leisure, healthcare and so on are too difficult to reach by bike or on foot. This is reflected in a single number, the so-called , rating all dwellings in cells of 1 ha (about 2.5 acres) from 0 (terrible) to 9.99 (all amenities right next door). Users can specify what their most frequent journey is, and this the can personalise their score by at most one point up or down.

The idea is that by raising awareness of the environmental impact of a dwelling, the ‘mobiscore’ will encourage people to move and live closer to the amenities. A laudable initiative? Maybe, but it got a rather lukewarm reception. So what is wrong with it?

What would make you move from a red house to a blue one? (source)

One problem is inevitably the broad brush approach to quantifying the environmental impact of a home. It relies on assumptions and averages, which fail to capture the varied circumstances of individual households. The actual footprints of two similar neighbouring houses, one occupied by a newly retired couple in good health, the other by a young family with three kids who need shuttling not just to school, but to ballet, football, guitar lessons and what not will be rather different.

This is not the main issue, though. The real question is how this will change the behaviour of a household. People don’t move house all that often, least of all the firmly rooted Flemish. In 2009, just 4.1% of them moved to a different town — once every 25 years on average. The chance that a settled household will move house just because they have a bad mobiscore is low.

Maybe it would work for new households? How would they behave? Picture a young couple. They have found a pretty house with a garden (great for the kids later). And it is affordable too! Now they discover that it has a low mobiscore, because it is in a small village. They check out similar houses in a larger town, but these cost a lot more. For the same price as their dream house, all they can find is a smaller house without a garden, or a flat. Imagine them opting for such an urban home: “Sure, the kids won’t have a garden to play in, but hey, look at our mobiscore!” Can you? Neither can I.

Living in cities is more energy-efficient, but energy-efficiency is not the only criterion people use to choose where to live. People choose their home primarily with their heart, not with their mind. Of course those who choose to live in the countryside are generally well aware of the sacrifices this brings with it, like longer commutes and more money for petrol. But they weigh this up against the upsides, like a more pleasant environment and more space. For many, that makes it all worth it.

To think that an instrument like the mobiscore will have any material influence on this decision verges on delusion. Encouraging people to reduce their environmental footprint will be a matter of changing many everyday behaviours, not of trying to affect an infrequent decision of great emotional importance, especially if that involves a questionable number with little emotional (or for that matter, any) significance.

Developing effective nudges takes thought and insight, and the only criterion for success is whether they affect people’s behaviour. On that criterion, the mobiscore is likely to be a big fail.

Originally published at on June 28, 2019.

Thank you for reading this post — I hope you enjoyed it. Please do share it far and wide — there are handy Twitter and Facebook buttons nearby, and you can click here to share via LinkedIn, or simply copy and paste this link. See all my other posts (I publish one every week) here. Thanks!

Accidental behavioural economist in search of wisdom. Uses insights from (behavioural) economics in organization development. On Twitter as @koenfucius

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