Humans didn’t exist the last time there was this much CO2 in the air

This story was originally published by Grist and appears here as part of the Climate Desk collaboration.

The last time atmospheric carbon dioxide levels were this high, millions of years ago, the planet was very different. For one, humans didn’t exist.

On Wednesday, scientists at the University of California in San Diego confirmed that April’s monthly average atmospheric carbon dioxide concentration breached 410 parts per million for the first time in our history.

We know a lot about how to track these changes. The Earth’s carbon dioxide levels peak around this time every year for a pretty straightforward reason. There’s more landmass in the northern hemisphere, and plants grow in a seasonal cycle. During the summer, they suck down CO2, during the winter, they let it back out. The measurements were made at Mauna Loa, Hawaii — a site chosen for its pristine location far away from the polluting influence of a major city.

Increasingly though, pollution from the world’s cities is making its way to Mauna Loa — and everywhere else on Earth.

In little more than a century of frenzied fossil-fuel burning, we humans have altered our planet’s atmosphere at a rate dozens of times faster than natural climate change. Carbon dioxide is now more than 100 ppm higher than any direct measurements from Antarctic ice cores over the past 800,000 years, and probably significantly higher than anything the planet has experienced for at least 15 million years. That includes eras when Earth was largely ice-free.

Not only are carbon dioxide levels rising each year, they are accelerating. Carbon dioxide is climbing at twice the pace it was 50 years ago. Even the increases are increasing.

That’s happening for several reasons, most important of which is that we’re still burning a larger amount of fossil fuels each year. Last year, humanity emitted the highest level of greenhouse gas emissions in history — even after factoring in the expansion of renewable energy. At the same time, the world’s most important carbon sinks — our forests — are dying, and therefore losing their ability to pull carbon dioxide out of the air and store it safely in the soil. The combination of these effects means we are losing ground, and fast.

Without a bold shift in our actions, in 30 years atmospheric carbon dioxide will return back to levels last reached just after the extinction of the dinosaurs, more than 50 million years ago. At that point, it might be too late to prevent permanent, dangerous feedback loops from kicking in.

This is the biggest problem humanity has ever faced, and we’ve barely even begun to address it effectively. On our current pace, factoring in current climate policies of every nation on Earth, the best independent analyses show that we are on course for warming of about 3.4 degrees Celsius above pre-industrial levels, enough to extinguish entire ecosystems and destabilize human civilization.

Climate change demands the urgent attention and cooperation of every government around the world. But even though most countries have acknowledged the danger, the ability to limit our emissions eludes us. After 23 years of United Nations summits on climate change, the time has come for radical thinking and radical action — a social movement with the power to demand a better future.

Of the two dozen or so official UN scenarios that show humanity curbing global warming to the goals agreed to in the 2015 Paris Accord, not one show success without the equivalent of a technological miracle. It’s easier to imagine outlandish technologies, like carbon capture, geoengineering, or fusion power than self-control.

Our failed approach to climate change is mostly a failure of imagination. We are not fated to this path. We can do better. Yes, there are some truly colossal headwinds, but we still control our future. Forgetting that fact is sure to doom us all.