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fragile than people think.
It's subject to radical shifts that can be
so quick and extreme
that it can change the course of history.
A potential big chill could be caused by something as subtle
as a deviation in ocean currents in the North Atlantic.
The climate catastrophe might begin
with temperatures bouncing up and down
from cold to hot, and back, for decades.
Paradoxically, as the southern regions heat up,
the northern areas become much colder.
Some experts project a 10-degree drop
in average winter temperatures in some areas.
The results, freezing winter storms
paralyze western Europe.
Stinging winter temperatures grip
the eastern seaboard of the United States.
Raging ice storms with high-wind velocity batter New York.
Temperatures continue to drop.
Boston reels under the weight of the most brutal
winter in its history.
As the relentless winter persists, punishing snow
and windy ice storms blanket the entire northeast coast.
In Europe, the winters also stretch into months
of unending freezing temperatures.
London's cold, wet winters twist
into a deadly series of ice storms.
Paris is frozen in stark relief to what it once was.
Berlin is a snowbound relic of the past.
Some scientists predict that this sudden change in climate,
including a big chill in the north,
could occur within our lifetime.
- I think there are several things that people
don't realize about the climate. First of all,
that it is changing, that that is a given.
And the only question is how fast,
and how far, and where it will settle out.
And that it can change rather dramatically.
[narrator] Ironically, the same shift in climate
may cause not only near-Arctic conditions, possibly creating
a mini Ice Age in parts of North America and Europe
but also massive drought
and more severe storms in other regions.
It's not only the speed at which these climate
changes will occur, some say within a decade,
but also the unpredictable nature of the changes
that make the impact potentially lethal.
- As we move into the future, if the climate state is such
that we can have severe storms
and severe weather events
coming in every year or every other year,
that's not normally what we deal with, and that's not normally
what society is prepared to cope with.
And adapting to that kind of extreme is very difficult.
We don't know what to prepare for.
[narrator] Around 1300 AD,
the weather mysteriously began changing.
Historical data taken from crop yields
and other public records show a small drop in temperature.
But this minor degree change in temperature was enough
to trigger the Little Ice Age,
a prolonged period of colder weather in Europe
that would have disastrous consequences.
Ultimately, this slight shift in climate would play
a part in the spread of the Black Death
and the social upheavals that would lead
to the American and French revolutions.
Researchers from Woods Hole Oceanographic Institution
look for clues about past climate change
by digging sediment cores from the ocean floor.
They have discovered intriguing evidence of the Little Ice Age.
- The seafloor is a repository for,
uh, for shells of animals that grew
in the overlying waters and for sediments that wash off land.
And these layers accumulate in the cores,
and we get a record that might be a hundred thousand
or even a million years long.
- The oceans are warming. Almost all the glaciers
on the planet have gotten smaller
over the last hundred years.
You're getting reductions in sea ice in the Arctic.
Things are happening earlier in the spring and lasting
farther into the fall than they did in the past,
and so there's this great number of indicators
that say, yes, the planet is warming.
[narrator] This rise in the ocean temperatures
may cause a shutdown of the thermohaline circulation,
the system that brings warmth to the North Atlantic region.
- The total heat capacity of the ocean
is 1100 times that of the atmosphere.
So in my mind, we really should be trying to understand
what's going on in the ocean to
understand our future climate.
[narrator] Researchers from Woods Hole Oceanographic
Institution utilize many tools
to study the changing ocean.
Remote controlled devices called floaters
track changes in the ocean's condition.
- They're sort of like weather balloons for the ocean
that drift at depth for ten days,
then come to the surface,
recording the temperature and salinity as they rise,
and they transmit that data to a satellite.
And we have a program to deploy
thousands of these around the global ocean,
and thereby, for the first time,
monitor the ocean heat
and salt content on a continuous basis.
This is a revolutionary new tool
for seeing climate processes acting in the ocean.
[narrator] Using the data transmitted by tools
like floaters, scientists create computer models that track,
and then project, climate changes.
Recently, researchers have found evidence
of a disturbing development.
Global warming is melting glaciers and ice sheets,
causing an increase in fresh water flowing
into the thermohaline circulation,
a process they call freshening.
This fresh water could throw off the critical balance
between temperature and salinity that powers
the thermohaline circulation.
Using the latest in scientific data and computer
visualizations, we get a terrifying glimpse
at the impact of extreme and abrupt climate change
in our future.
Not just freezing temperatures in the north,
but also monster hurricanes, massive storms,
and in some areas, endless drought.
- If you look at the potential for the damage
done by climate change, you can easily see
how climate change could be a weapon of mass destruction.