Environment

Decarbonizing aviation remains challenging because energy-dense jet fuels dominate beyond short-range operations, while batteries impose severe range and payload penalties. Here we evaluate a new infrastructure pathway in which utility-scale solar farms equipped with solar phased arrays wirelessly beam microwave power to hybrid-electric aircraft during cruise. Integrating 143,152 U.S. flight trajectories, 5,712 solar farms and wireless power transfer models, we quantify the spatial, temporal, and operational potential of this concept at continental scale. We find that benefits are highly...

We implement a field experiment at a U.S. university to identify the effect of revealing peers’ rank, in terms of previous voluntary service, on future voluntary service of individual faculty members. We find that revealing a service ranking in the lowest quartile leads to significantly higher response rates than disclosing a median quartile ranking. Beyond informing the department head, sending a direct email to individuals does not have an incremental effect on average voluntary service responses, though it causes significantly higher new response. Finally, we find the above effects are...

Transportation contributed nearly 25 percent of global anthropogenic carbon dioxide (CO2) emissions in 2007. The level of emissions depends on the distances people and goods travel, the modes with which they use, the fuel consumed per kilometer moved and the CO2 associated with each fuel. Different developed countries have complied to different levels of emissions reductions targets, while developing countries are not subject to any national agreement to reduce their emissions levels. For the United States, President Obama has pledged to reduce CO2 emissions between 14 percent and 17...

We review aggregate trends in CO2 emissions from road transport in Latin America. Comparison with other regions, as well as with automobile ownership and use suggests that road transport the emissions in this region are closely connected to high automobile ownership and use. Examination of detailed estimates of vehicle stocks, use and fuel intensity as well as data from four large metropolises in the region confirms this suggestion. The same data show that it is cars that are the main reason for congestion, high levels of air pollution, and other transport related externalities in urban...