Here's why:
* Earth's temperature: The Earth's surface and atmosphere are relatively cool compared to the Sun. Objects at lower temperatures emit radiation at longer wavelengths.
* Blackbody radiation: The Earth, like any object, emits radiation based on its temperature. This is known as blackbody radiation. The peak of this radiation curve for Earth falls within the infrared range.
* Greenhouse effect: Some of this infrared radiation is trapped by greenhouse gases in the atmosphere, contributing to the Earth's warming. This is why infrared radiation is so important to understanding climate change.
While the Earth also emits some radiation in other parts of the spectrum, like visible light (which is why we can see the Earth), the vast majority of its outgoing radiation is in the infrared.
