IDIOT’S GUIDES: SCIENCE MYSTERIES EXPLAINED
If we reverse climate change, could the sea level drop
As the Earth warms, glaciers and ice caps melt, adding their water to the ocean. Plus,
a hotter sea expands, further raising sea levels. If we master the art of reducing global
warming, could we end up with a much lower ocean and a whole new set of problems?
The sea level on Earth changes over time, swinging from extreme highs to extreme lows. The changes
humans are making are minimal, but they could still be disastrous for us ….
Over geological timescales—millions of years—
there’s nothing static about the surface of the
Earth. Continents move around. Mountain ranges
are pushed into the sky and eroded back down by
rain and wind. The ocean itself ebbs and ﬂows,
rushing to cover huge areas of land and then re-
treating many miles from previous coastlines.
That’s big-picture, deep-time stu. But on
smaller scales—less than a million years—there’s
still plenty of change. One of the biggest variables is
the sea level.
Earth routinely moves in and out of so-called
ice ages. When global temperatures drop by sev-
eral degrees, more ice forms in high latitudes.
This ice is drawn, via evaporation, from the
ocean. More ice on land, less water in the sea, so
sea levels drop.
We’re currently living in a post-glacial
world. A geological spring, if you like, of a planet
recovering from an ice age of pretty average
intensity. In fact, it’s likely the planet would be
either stable or warming slightly even without
human input. But as the ice melts, the water
returns to the sea and the sea rises. Water also
expands as it warms, and in an ocean, even a few
degrees is enough to raise the surface by several
Only 8,500 years ago, there was a broad
sweep of land between England and the west
coast of the Netherlands. Archaeologists call it
Doggerland after the Dogger Bank, which is now
a ﬁshing ground.
Seabed archaeological digs have found lots of stone
tools in Doggerland, along with the remains of animals
like deer and lion (and human, too). In fact, most of the
really good archaeological sites for stone-age human
remains are actually underwater, just o the coasts of
Europe and far eastern Russia.
The point here is that before humans even developed
the technology to start pumping CO
into the air, we
survived a catastrophic sea level rise. Some scientists
estimate we lost 40 percent of our hunting grounds to
the rising tide. The land bridge from Russia to Alaska
was ﬂooded, along with a huge plain between Papua New
Guinea and Australia. The sea may have risen as much as
300 feet in the last 10,000 years as the last of the ice sheets
Today, we live on the edge of a drowned landscape.
Even if we cease CO
production and return the atmo-
sphere to the precise state it was in back in, say, 1800, it’s
unlikely the sea would drop signiﬁcantly.
Reclaiming those ancient ﬂooded countries would
mean the planet would have to go back into an ice age. Yes,
we’d get back Doggerland, but we’d lose all of Canada—and
the United States to below Chicago—under ice sheets.
If the sea rises and falls naturally, why are we so
worried about human-induced sea level change? Because
we’ve built so much infrastructure so close to the coast.
Only a couple dozen feet of extra depth—barely a statisti-
cal glitch on the scale of the planet’s entire history—could
leave New York ﬂooded and do trillions of dollars’ worth
It’s likely that one day, hopefully thousands of years
from now, we will have to face the challenge of really
signiﬁcant sea level change. We should consider reducing
man-made increase as a practice now.