Celebrate Earth Day by tuning in to Perpetual Planet: Heroes of the Oceans on April 22 on National Geographic. | National Geographic TV

Our planet is getting warmer. Every year, NASA and NOAA calculate the average surface temperature around the globe. These annual temperature data make up the global temperature record – and it’s how scientists know that the planet is warming. Red spirals in this visualization indicate years with warmer-than-average temperatures. The visualization “turns red” after 1975, showing that most of Earth’s warming has occurred in the last several decades. Overall, the average global temperature on Earth