Without the Sun, Earth’s land, water, and air would all be frozen solid! Life on Earth would cease to exist. That’s because almost all living things rely on the steady light and heat of the Sun. The Sun’s heat makes liquid water on our planet possible. And all life that we know of—from bacteria to elephants—needs liquid water to survive.
Changes in the Sun’s brightness can change global temperatures. Luckily, the Sun, like most middle-aged stars, shines steadily and reliably. Changes in its brightness are not causing global warming today, although they probably have in the distant past.
Aside from its heat and visible light, the Sun also shines in ultraviolet (UV) light. Ozone in Earth’s upper atmosphere blocks much of the UV. However, pollution can weaken the ozone shield. Then the Sun’s UV light can harm living things on the ground and in the top layers of the oceans. Even when the ozone shield is strong, the UV that gets through help form smog from car exhausts and other pollution.
People can harness the heat and light of the Sun to generate electricity. Solar energy is becoming cheaper and more widespread. Someday it could supply most of our electricity. That would allow us to burn less fossil fuels like coal or oil. The burning of these fuels causes global warming by emitting carbon dioxide into the atmosphere, where it traps the Sun’s heat.