Climate Change: Been There, Done That

Okay, yes, climate change is scary.

But the truth is, the planet has seen it before. Many times. Sometimes it's been fast. Sometimes it's been slow. It's just how things are here on Earth.

Here's a short primer on the history of climate change (based on information provided by the National Oceanic and Atmospheric Administration, better known as NOAA):

Periods of extended glaciation occurred long ago, including 720-770 million years ago and 575-610 million years ago, when ice sheets covered whole continents. In fact, some scientists believe that the Earth was once so cold that all its oceans were frozen.

At 250 million years ago, scientists believe that an asteroid hit the Earth, causing the deaths of most animals on the planet.

About 150 million years ago, the planet started to warm up. Some scientists say this happened because so much carbon dioxide was produced by volcanoes. Carbon dioxide is a "greenhouse gas." It traps the heat of the sun inside the Earth's atmosphere. Without greenhouse gases, the Earth would be freezing cold, like Mars.

Another chunk of rock hit Mexico about 65 million years ago. The asteroid threw up so much dust that the sun was blocked and the planet cooled, killing the dinosaurs.

Around 55 million years ago, more greenhouse gases escaped the center of the Earth, warming the planet again. It was so warm that the ice at the north and south poles melted. Alligators lived in Alaska, and crocodiles swam around the north pole.

At 50 million years ago, things started to cool off. Ice caps grew. The oceans got colder and colder, until a huge sheet of ice covered Antarctica. In North America, the temperature dropped by 12 degrees.

Around 34 million years ago, the Antarctic ice sheet began to form.

About 10 million years, hominids (human-like animals) evolved in and around the Mediterranean Sea. The sea dried up and re-flooded several times, changing the weather around the world

About 1.8 million years ago, ice ages started to come and go. The Earth has been icing over and melting ever since.

About 71,000 years ago, a volcano in Indonesia threw a huge amount of ash and rock into the atmosphere. Some scientists think this eruption could have thrown the planet into a six year volcanic winter and 1,000 year instant ice age

At 8,200 years ago, freezing cold lakes in Canada suddenly flooded south when a dam broke. This event may have set off a 400-year-long "mini ice age."

Around 6,000 years ago, the temperature was suddenly warmer. Why? The answer remains a mystery.

A thousand years ago, there were terrible droughts in the American Southwest. Was this what pushed the Pueblo Indians out of their ancient homes in Arizona? Drought may also have played a role in ending the Mayan, Incan and Egyptian cultures. Some scientists think that a volcano could have created this climatic disaster.

From 1000 to 1400 A.D., the Earth was just a little warmer than it is now. But then, between 1400 and 1800 A.D., the Earth cooled down. Glaciers grew, covering more of the poles with ice.

There's no doubt about it: things are heating up today. It's not obvious where today's climate change is headed -- and the outcomes could be drastic. For us. It helps, though, to put it all in context. When it comes to climate change, the reality is that we've been there and done that.

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