Earth energy budget diagram, with incoming and outgoing radiation (values are shown in W/m^2). Satellite instruments (CERES) measure the reflected solar, and emitted infrared radiation fluxes. The energy balance determines Earth's climate. Ethan Siegel Senior Contributor Jan 2, 2019 Let's play pretend for a moment. Pretend, if you can, that you've never heard about the idea of global warming before. Pretend you've never heard anyone else's opinions on the matter, including from politicians, scientists, friends or relatives. Pretend that there are no related concerns, like the economy, our energy needs, or the environment. If you were going to make a genuine inquiry, there would instead be only two questions to ask and answer: is the Earth warming or not, and if so, what's the main cause? This is a question that was tailor-made for the enterprise of science to answer. Here's how we can figure it out for ourselves.
There are really only two things that determine the Earth's temperature, or the temperature of any object that's heated by an external source. The first is the energy that goes into it, which is primarily energy produced by the Sun and absorbed by the Earth. The second is the energy that leaves the Earth, which is primarily due to the Earth radiating it away.
