From protecting our waterways to reducing overfishing, we've made a lot of progress since the first Earth Day. Take a look at five big wins in the 46 years since 1970.
Warmer winters or hotter summers: which will have greater influence on U.S. energy demands this century?
Since 2004, researchers in NOAA’s Global Monitoring Division have released the Annual Greenhouse Gas Index: a single value that compares the total warming effect of each year's concentrations of heat-trapping gases to 1990 levels.