Students, gardeners, retirees, and other volunteers taking part in a nationwide initiative, Project BudBurst, are finding hints that certain plants are blooming unusually early.

Current observational tools cannot account for roughly half of the heat that is believed to have built up on Earth in recent years.

There’s only so much air to go around. Since we inhale trillions of molecules with every breath, a few of them may have been exhaled by people who lived hundreds or thousands of years ago.