Ongoing drought - and increasing temperatures - have reduced water flow in the Colorado River, with more dramatic reductions expected. This ongoing, unprecedented event threatens water supplies in cities in the U.S. West and some of the most productive agricultural lands anywhere in the world.

The ice sheets are melting from both above and below, say scientists.

Cottonwood trees in the American West are a nuisance to some and a treasure to others. They yield shade, beautiful foliage and, in June, a kind of warm, fluffy "snow."

More tornadoes occur in the U.S. than any other country, mainly in the Great Plains, Midwest and southern states. Two meteorology professors answer questions.

Rock is apparently no match for Anthophora pueblo bees. Scientists have found their sandstone nests scattered across dry lands in the U.S. Southwest.

A strong G3-class geomagnetic storm sparked auroras over both poles of Earth this past weekend. Hunter Davis, at the South Pole, captured images.

This year's list includes a spider and an ant with names drawn from popular books, a pink katydid and an omnivorous rat.

Happening now in Denmark: "bright nights," when the sun is never far below the horizon. Photographer and videographer Adrien Mauduit tells the story and provides stunning imagery.

And, at both the poles, sea ice extents were at or near record low levels, according to the National Oceanic and Atmospheric Administration.

Our teeth evolved from the same genes that make the bizarre beaked teeth of the pufferfish, according to new research.