Scientific evidence clearly indicates that the earth is warming and that this warming is already affecting our climate. This global warming is due largely to human activity, which is responsible for the emission of greenhouse gases, especially CO2 and methane. According to climatologists, changing human energy-consumption behaviors now appears to be the best, and probably the only possible option, given the urgency of the situation. However, changing human energy-consumption behaviors is not easy. Psychological studies have identified general psychological barriers that limit or hinder these behavior changes (limited cognition, ideologies, comparison with other people, perceived risk...), and it has proposed different kinds of interventions (e.g., information, feedback, social motives, financial incentives...). However, it is clear that psychologists must work with other scientists in order to find better solutions for changing behaviors. Scientists from the human-computer interaction (hci) field have also been concerned by climate change and have developed different approaches to reducing energy and material consumption. Principles such as linking invention and disposal, promoting renewal and reuse, quality and equality, de-coupling ownership and identity, and using natural models and reflection have been proposed to reduce the consumption of both energy and resources while developing software and hardware. In addition to those technology-centered principles, two other principles have been proposed: making people aware of their energy consumption and persuading people to change their consumption behaviors. Making people aware of their energy consumption has been facilitated by ambient awareness systems (devices and physical systems, visualizations...) and by attitude and behavior changes through persuasive technologies. Although scientists in this field have been creative, the impact of their propositions has seldom been evaluated. This paper briefly reviews the topics listed above, discusses some issues, and proposes some research avenues.