Daily Climate: Big dams built in the tropics to produce hydroelectricity have long been highly controversial - and data gathered in Laos by a French team studying methane emissions confirms that dams can add to global warming, not reduce it.
In many rocky regions low on vegetation and population, such as in Iceland and other northern mountainous regions, the production of electricity from hydropower is clearly a net gain in the battle against climate change.
In Asia, Africa and South America, however, masses...