Page 9 - A Hot Mess: How the Climate Crisis Is Changing Our World

allowing life on Earth to exist. Everything from the oceans and soil to
plants and animals absorbs heat from the sun. Clouds, snow, and ice
are among the things that reflect the sun’s heat back, so having them
around is crucial for keeping the planet from getting too hot.
Here’s where the atmosphere comes into play. The vast majority of
it—about 99 percent—is made up of just two elements, nitrogen and
oxygen. The last 1 percent consists of lots of other gases, including
carbon dioxide, methane, nitrous oxide, halocarbons, and water
vapor. These are called greenhouse gases because they produce what’s
known as the greenhouse effect.
Even though they’re just a small part of the atmosphere,
greenhouse gases have a big impact. When Earth’s surface reflects
some of the sun’s energy back out, the greenhouse gases in the
atmosphere block part of that heat from escaping. That keeps the
planet warmer. It’s not a perfect analogy, but the process is a bit
like how the glass walls of a greenhouse trap heat, which helps the
plants inside grow, even in cold weather (and that’s what gives the
greenhouse effect its name).
Greenhouse gases aren’t bad in and of themselves. They’re
supposed to be in the atmosphere. They’re one of the reasons why
Earth is warm enough to support the kinds of plant and animal life
that live here, including us. Without greenhouse gases, the average
surface temperature of Earth would be almost 60°F (15.6°C) colder.
The problem is how much of those gases is in the atmosphere.
The amount of carbon dioxide there now is higher than it’s been in at
least the last eight hundred thousand years. In other words, it’s higher
now than it’s been at any point in the time that Homo sapiens have
existed. Humans like us have only been around for about 40 percent
of that time.
Earth is more than 4.5 billion years old, and its climate has
changed many times in that span. When the planet was new and
for millions of years after that, it was incredibly hot. But over time,

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