Have you ever wondered why you live on a beautiful blue watery planet and not a frozen ball of ice?

That's exactly what the French scientist Joseph Fourier wondered almost 200 years ago.

He calculated Earth was far enough away from the sun that it should be much colder-- way colder, like below freezing, instead of warm and comfortable.

Fourier noted that while sunlight can shine through the gaps in Earth's atmosphere to warm the surface, the heat our planet gives off doesn't pass so easily back into space, just like how sunlight warms up a greenhouse.

Fourier's simple observation came to be known as the greenhouse effect, and gave birth to a new way of thinking about the world, the science of Earth's climate.

In the 200 years since, we've made a lot of progress in figuring out how Earth's climate works, how it's changing, and why.

But why have we had such a hard time acting on that knowledge?

At the start, there was just a lot we didn't know.

But the next big eureka moment came in the 1850s.

Scientists Eunice Foote and John Tyndall figured out that adding more of certain types of gas, like carbon dioxide, to Earth's atmosphere would make it trap more heat.

And in the 1890s, Swedish scientist Swante Arrhenius made the first mathematical predictions of how much that extra carbon dioxide would heat the earth.

But most people simply hadn't heard about any of this.

And if they had they might not have believed it, since few people even imagined that humans could affect something as big as the climate.

But Earth's human population soon took a steep upward turn, partly because fossil fuels were transforming the way we lived.

A British engineer named Guy Calendar suspected this might have a bigger impact than people thought.

In 1938, he looked at atmospheric and temperature data from around the world in more detail than anyone ever had.

He showed for the first time that not only was burning fossil fuels increasing the amount of CO2 in the atmosphere, but Earth's average temperature was rising in response, just like Arrhenius said it would.

A growing number of scientists realized we were performing an unprecedented experiment with an uncertain outcome.

They eventually gave it a name, global warming.

More measurements of the atmosphere continue to tell the same story.

We were adding carbon dioxide to Earth's insulating layer.

That warmed the air, but we discovered that it was also changing the amount of ice at the poles, the patterns of rainfall on land, and even the chemistry of the ocean itself.

So we gave it a new name, climate change.

What's more, by analyzing ancient air bubbles trapped in ice millennia ago, we realized that CO2 has been the main control knob on Earth's climate for hundreds of thousands of years.

Looking at the history, it's clear by the second half of the 20th century, we understood the main causes of climate change.

And they were surprisingly simple.

We knew what was happening and why.

So why didn't we do anything about it then?

Could it be that we just didn't want to know?

It's not like scientists were keeping this knowledge to themselves.

In 1959, physicist Edward Teller stood in front of every major oil executive and cautioned that by burning fossil fuels, we were changing Earth's climate.

[audience booing] In 1965, scientists warned US President Lyndon Johnson about risks from climate change.

But it took until 1992 for us to sign a global treaty calling for lower emissions.

And we're still struggling to act today.

That's partly because climate change is a big, complicated problem, maybe the biggest humanity's ever faced.

The modern world was built on and still depends on fossil fuel energy, at least for now.

So adapting to and stopping climate change will require revolutionizing much of how we live.

That would be really tough to do.

And it's difficult to even get our heads around what it might look like, which brings us to another big reason we find it difficult to act-- our brains are just bad at processing a problem like climate change.

I mean, the gas that causes it is literally invisible.

And the changes play out over decades across the entire planet.

When we do think about it, it can easily feel far away or even overwhelming.

We know what's happening, and we've known it for a long time.

Climate change will affect us all, no matter where we are or how we live.

Solving it can't wait for tomorrow.

And we can't wait for other people to solve it for us.

And that's why we're making this show, to talk about how the climate is changing and how we can make earth cool again.

Let's get started cleaning up this hot mess.