3 Hasn’t the Earth always warmed and cooled?

You may have wondered, “Hasn’t the Earth always had times when it was hotter and cooler?” Earth has gone in and out of Ice Ages. Isn’t what is happening now just like what happened in the past? The Earth’s climate has gone through periods of warming and cooling. But the rapid warming we are experiencing in the 20th and 21st centuries is NOT caused by the same things as before. In the past, natural forces caused the warming. Now, human activities are the primary reason. To understand the difference between what happened before and what is happening now, we first need to learn about the layers of Earth’s atmosphere, how Earth’s Radiation Budget works, and factors that impact Earth’s Radiation Budget.