If technology is to save us from climate change, it has some tough challenges to master: taming wave, wind and sun, cheaply scrubbing carbon dioxide from the air or mastering fusion.
But a growing number of people think another should be added to the list: mastering human nature. This "persuasive technology" would sway people to adopt less polluting behaviour and may come in the form of new gadgets and online services or new features for existing technology.
Energy savings from behavioural change can be dismissed as advanced marketing techniques and may seem trivial compared with the esoteric materials science that is needed to harvest solar energy more efficiently. But there is much to be gained.
Last week New Scientist reported that US emissions could be cut by more than 7 per cent if people changed their ways at home. Separate studies in US, Dutch and British homes have reported that 26 to 36 per cent of domestic energy use is "behavioural" – determined by the way we use machines, not the efficiency of the hardware itself.
This means that "machines designed to change humans", as the persuasive technology group of Stanford University, California, calls them, could save us huge amounts of energy and money.
Many projects are trying to make that happen, with two main motivations. One is to understand which facets of human nature can be manipulated to change behaviour. The other is to develop technical strategies to do so.
A simple technique underlying many projects is to provide read-outs of people's energy use, in situations like the home where it has historically been hidden. It is well known that giving drivers feedback on fuel efficiency, for example, leads them to use less fuel. The information-rich dashboard of Toyota's hybrid Prius and Ford's new fuel-efficiency "vine", which grows leaves when you save fuel, are good examples of this approach. Studies of home power meters suggest they encourage homeowners to cut energy use by 10 per cent on average.
Persuasive tech that can track the effect of everything you do is the next logical step. For instance, a number of teams are working on cellphone apps that use GPS to guess what you're doing, and what that means for your carbon footprint.