Up in the Air: Did Dinosaurs Get Cold in the Winter?

When it’s summer in Canada, there is more oxygen in the atmosphere than in the winter.

And, when it’s winter, there’s more carbon dioxide in the atmosphere than in the summer, says Anais Orsi, a polar climate scientist who teaches at the University of British Columbia.

That’s because the oxygen in our atmosphere is a byproduct of life on Earth.

When it’s summer in the northern hemisphere, the large number of plants photosynthesizing increases the total amount of oxygen in the atmosphere.

In the winter, the plants drop their leaves to hibernate. Oxygen levels drop and CO2 levels rise as animals use these gasses to breathe.

Before life happened on Earth, there was almost no oxygen here.

Earth’s atmosphere has gone through some big changes in its long history as life evolved!

We’ve always had CO2 in the atmosphere, which scientists measure in parts per million.

In fact, 485 to 444 million years ago, during the Ordovician period At the start of the Ordovician, most life forms existed in the seas. Early ancestors of insects and spiders were among the first to experiment with life on land by developing primitive respiratory systems. , there was way more CO2 in the atmosphere than there is now, says John Clague, an earth scientist and officer of the Order of Canada.

This is when the very first plants and animals were trying out living on land instead of the ocean.

The planet was 10 degrees Celsius warmer and had 3,000 to 9,000 ppm of atmospheric CO2.

That’s way more than the amount of CO2 we’ve had in the atmosphere for the last million years, when the planet went through a series of ice ages, called glacials, and warmer in-between eras, called interglacials, completing a cycle every 100,000 years or so.

During a glacial period, atmospheric CO2 was around 180 ppm. During an interglacial period, it was closer to 280 ppm, Orsi says.

A lot of the CO2 is stored in the ocean when it’s cold and then released into the atmosphere when it warms, she adds.

We know atmospheric CO2 had fluctuated throughout Earth’s history because scientists can analyze really old ice samples, Orsi says.

Scientists drill deep into ice sheets in Greenland and Antartica to find samples of ice that froze hundreds of thousands of years ago. They look at tiny air bubbles trapped when the ice formed to measure what the atmosphere was like in the past.

The oldest ice sample Orsi worked on was 800,000 years old and other researchers have found ice that is 2.7 million years old.

We can find these still-frozen ice samples because the planet is still in the middle of the Pleistocene Ice Age, which started about 2.7 million years ago and continues today.

That means major ice sheets in Antarctica and Greenland are still frozen. Earth is currently in an interglacial period of that ice age known as the Holocene Epoch which started 11,700 years ago, Orsi says.

It’s during the stable climate of the Holocene that some humans started to transition from hunter-gatherer societies to agricultural ones.

If you go back to when dinosaurs ruled the world from 245 to 66 million years ago “the planet had little to no glacial ice,” Clague says.

About 25,000 years ago during the last glacial period, one-third of the planet was covered in ice, stretching from the arctic and covering North America, Europe and Eurasia. Because so much water was stuck on land in the form of ice, the ocean was 125 metres lower than it is today — that’s as tall as most of the buildings in downtown Vancouver!

So, did dinosaurs get cold in the winter?

Clague says, "To my knowledge, no one has a 100% for-sure answer to that question, but I think I would say 'no’.” 

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