Humankind’s effect on the Earth has been so powerful that our ancient presence on the planet staved off an ice age thousands of years ago, and the emissions of greenhouse gases in the modern age have put off the next one for another 100,000 years.
“The bottom line is that we are basically skipping a whole glacial cycle, which is unprecedented,” said CNN columnist John D. Sutter. “It is mind-boggling that humankind is able to interfere with a mechanism that shaped the world as we know it.”
The new study shows that far before post-industrial humans started pumping tons of greenhouse gases into the atmosphere, civilization-building activities — like agriculture, fires, and deforestation — kept an upcoming glacial cycle at bay, allowing the population to flourish and grow, the Washington Post reported.
To understand what this means, it’s important to first understand exactly how the Earth dips into a deep freeze. Two key phenomena determine this cycle — one outside our control, and one very much influenced by our behavior, like greenhouse gases.
We can’t control the Earth’s Milankovitch cycles, which refer to how the planet orbits the sun and spins on its axis over time, an activity which changes slightly over thousands of years. These changes effect show much sun falls on the Earth and where, influencing seasons and whether or not ice builds up on land.
What we can control is how much carbon dioxide is in the atmosphere, by how many trees we cut down or how much greenhouse gases we pump into the air. Both of these things transfer carbon from the land into the atmosphere. As we all know, carbon dioxide traps heat and causes warming, independent of those Milankovitch cycles.
And if there’s enough of these greenhouse gases in the air, they can knock those natural cycles out of whack — and “make or unmake” an ice age.
But humans started to change their environment drastically far before the industrial era. It’s a theory the study authors haven’t really pushed too hard, but which other scientists consider to be likely. A few thousand years ago, the amount of carbon dioxide in the atmosphere was just high enough to keep the ice age away. That has left scientists to wonder — why were they higher back then?
Quite simply, human beings found plenty of other ways, beyond emitting dangerous greenhouse gases, to change the environment: cutting down trees, agriculture, and other civilization-building measures. And interestingly enough, these activities made sure that civilization would continue to grow. After all, such a drastic change in climate would really have put a hamper on our growth.
Climate scientist William Ruddiman wondered why this latest study didn’t consider this theory more seriously in their study.
“While there is little doubt that industrial-era … emissions are now forestalling any possibility of a new ice age, the evidence shown here suggests that this major human intervention started millennia ago.”
And since then, greenhouse gases have ensured that another deep freeze is very, very distant possibility. Even moderate interference in nature, like burning fossil fuels, could delay the next glacial cycle until everyone on Earth is long dead and gone.
“As far as the human power is concerned, the main lesson is that by burning fossil fuel over just one century, we will affect climate for at least 100,000 years or even more,” lead researcher Andrey Ganopolski told CNN.
Keeping an ice age bay may sound like a great thing, but Sutter has warned that global warming is still a serious threat and if the planet’s temperature climbs two degrees, our low-lying islands will disappear, plants and animals will go extinct, and our weather will go haywire.
In other words, greenhouses gases delaying another ice age is not a good thing, no matter how nice it sounds not to have a massive ice sheet sitting atop North America.
“But it should be said clearly that global warming is not a positive trend. This is not an excuse to pollute. As we pump carbon into the atmosphere at an alarming rate we are seriously jeopardizing the viability of the planet and putting ourselves in very real danger.”
[Photo by Denis Burdin/Shutterstock]