Humans
didn’t exist the last time there was this much CO2 in the air
By
Eric Holthaus
2
May, 2018
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 confirmedthat 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.
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