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Scientists Study the
Impact of Water on
Climate |
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Scientists Study the
Impact of Water on
Climate
NASA picked Costa Rica
to study these questions
because it's one of the
places where large
amounts of water can
actually reach the
stratosphere. The reason
is massive thunderheads
during the rainy season.
By the end of this
century, the earth could
warm up by two degrees -
or 10 degrees. Sea level
could rise a few inches
- or a few feet.
Scientists aren't sure
because nothing to do
with climate change is
simple.
Take greenhouse gases,
for example, which trap
heat from the sun. The
most important
greenhouse gas isn't
carbon dioxide or
methane. It's water. And
scientists are still
trying to understand
what role water has in
global warming.
This summer, NASA sent a
team to Costa Rica in
search of more on
information on the
topic. One of their most
important research tools
was a sleek white jet
that looks like a U-2
spy plane. Actually,
it's a civilian version
of the U-2, called the
ER-2 — and it's is set
up for science.
During one flight, the
ER-2 spent the morning
gathering information
about the atmosphere 10
miles over head. But it
wasn't a perfect flight.
Paul Newman, of NASA
Goddard Space Flight
Center, learned that one
piece of the plane's
equipment didn't work.
"And it was not long
after takeoff that it
failed," Newman says.
But it's a minor
setback. The day before,
lightning punched a
small hole in another
NASA plane.
Clouds Crucial to
Life and Research
It's all part of
working in this area of
the tropics, which may
be the best place on
earth to learn more
about the role of water
in global warming.
"Water is a tremendous
greenhouse gas. It can
condense and form all
these clouds. Clouds can
reflect radiation.
Clouds can actually
insulate the surface, if
you got a cloud layer
overhead the surface
stays a little bit
warmer. So water is
really crucial to the
whole process," Newman
says.
To appreciate the
importance of water in
the atmosphere you have
to imagine what the
earth would be like
without it.
"If we didn't have an
atmosphere with water in
it, the earth's average
temperature would be
about 30 degrees
Fahrenheit below
freezing," says Brian
Toon, of the University
of Colorado and a member
of the Costa Rica team.
More Water Leads to
More Water
Water in the
atmosphere is absolutely
necessary.
Unfortunately, water
amplifies the effects of
other greenhouse gases.
"You add carbon dioxide
to the air, you burn a
fire, drive a car,
something like that, and
that carbon dioxide
floats up to the upper
atmosphere and blocks
some of the light from
escaping to space, so
the earth warms up a
little bit," Toon says.
That causes water in the
atmosphere to radiate
more energy. So the
oceans get warmer.
"And when you make water
warmer, as everybody
knows in their kitchen,
more water evaporates
and so the atmosphere
gets more water in it.
And that warms things up
even more. So, the net
effect of all this is is
that if you just put in
the carbon dioxide you
get a temperature
change, but all that
water gives you three
times more temperature
change than you get with
the carbon dioxide
alone," Toon says.
Water Multiplies
Effect of Other
Greenhouse Gases
Most water doesn't
linger in the
atmosphere. It falls
back to earth within a
week or so.
But in the past couple
of decades, it's become
clear that if water
reaches the stratosphere
it can stay there for a
long time, just like
other greenhouse gases.
It's also clear that the
amount of water in the
stratosphere is
increasing.
What's not clear is
whether that extra water
is the result of human
activities and whether
it's accelerating global
warming.
NASA picked Costa Rica
to study these questions
because it's one of the
places where large
amounts of water can
actually reach the
stratosphere. The reason
is massive thunderheads
during the rainy season.
Newman says these storms
create powerful updrafts
that carry water miles
into the air.
"In fact, some of these
clouds do poke up to
very high altitudes,
60,000 feet. And you get
cirrus particles, small
ice particles, the very
feathery kind of clouds
you see, they will come
off of these
thunderstorms," Newman
says.
And they transport water
into a part of the
atmosphere that is
normally very dry.
A flight took the ER-2
into high-altitude
clouds that were
discovered only a few
years ago. They're
cirrus clouds so thin
they're invisible from
the ground.
"We actually flew along
with the airplane and we
had a laser that shoots
out the bottom of the
plane and you could tell
that this sub-visible
cirrus was there, so we
actually measure it with
the laser," Newman says.
Scientists hope the
infra-red measurements
will show whether these
clouds are contributing
to the greenhouse effect
by reflecting heat back
to earth. That won't
make climate predictions
perfect. But it will
make them better. |
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Two ER-2 planes fly over San
Francisco. Planes like these record
atmospheric data as the fly.
NASA |
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