Although hydropower is broadly considered to be much more environmentally friendly than electricity generated from fossil fuels (e.g., earlier post), a new study by a team at Environmental Defense Fund finds that the climate impact of hydropower facilities varies widely throughout the world and over time, with some facilities emitting more greenhouse gases than those burning fossil fuels.

The researchers report their results in an open-access paper in ACS’ journal Environmental Science & Technology.

Currently, hydropower contributes two-thirds of the electricity generated from renewable sources worldwide, according to the International Energy Association, with thousands of new hydroelectric facilities either planned or under construction across the globe.

This popularity stems partly from the perception that hydropower is an environmentally friendly alternative to fossil fuels. It is commonly thought that the greenhouse gas emissions from hydropower plants are similar to those of wind-generated power facilities. However…