This document discusses what climate change is and how NASA monitors and measures changes in Earth's climate. It defines climate change as a long-term shift in weather patterns caused by increased greenhouse gases. NASA uses satellites to track rising sea levels, shrinking ice sheets, and variations in clouds and oceans over decades to understand how the climate is changing globally. Careful observation of these changes is important for planning and addressing the future impacts of our warming planet.

1. What is climate change?
Lesson 1
Stefka Pavlova, Kindergarten zname
na mira, Belene, Bulgaria

3. • Take a look outside your window.
• Is it hot and sunny?
• Is it cloudy and rainy?
• Is there snow on the ground?
• When you look out the window, you’re seeing what the
weather is like today.
• Weather is only temporary. For example, a blizzard can
turn into a flood after just a few warm spring days.
• Climate, on the other hand, is more than just a few
warm or cool days.
• Climate describes the typical weather conditions in an
entire region for a very long time—30 years or more.
• Keeping an eye on changing weather can help us plan
ahead.
• We know that if thunderclouds are forming overhead,
it’s probably a good idea to stay inside.

4. • But it’s important to keep an eye on changes in Earth’s climate, too. And NASA
has observed that Earth is getting warmer.
• Keeping track of Earth’s sea level is one way that we can know how quickly the
climate is changing.
• As Earth’s climate warms, ice in Antarctica and Greenland is melting. This causes
the level of the oceans to rise.
• NASA satellites can measure sea level rise from space.
• They can also track changes in the climate by measuring the clouds.
• We know that changes in the number, size or location of clouds could be caused
by a change in Earth’s climate.
• NASA satellites are always orbiting Earth, looking down at our oceans and clouds.
And they monitor Earth’s climate in other ways, too.
• It’s important to keep an eye on our planet and all the ways that it’s changing.
Right now, it’s the only one we’ve got!

5. What is climate change?
• Climate change describes a change in the
average conditions — such as temperature
and rainfall — in a region over a long period of
time. NASA scientists have observed Earth’s
surface is warming, and many of the warmest
years on record have happened in the past 20
years.

6. What are greenhouse gases?
• What are greenhouse gases?
• Greenhouse gases are gases in Earth’s atmosphere that
trap heat. They let sunlight pass through the
atmosphere, but they prevent the heat that the
sunlight brings from leaving the atmosphere. The main
greenhouse gases are:Water vapor
• Carbon dioxide
• Methane
• Ozone
• Nitrous oxide
• Chlorofluorocarbons

7. Water
• Water is essential for life on Earth. From
oceans to rivers to clouds in the sky, NASA
satellites are observing where Earth’s water is
found--and how that is changing over time.

8. How Do We Measure Sea Level?
• NASA measures sea level around the globe
using satellites. The Jason-3 satellite uses
radio waves and other instruments to
measure the height of the ocean's surface –
also known as sea level. It does this for the
entire Earth every 10 days, studying how
global sea level is changing over time.

9. How Do We Measure Sea Level?
• Rising sea level is one of the clearest signs of
global warming. It's also one of the biggest
problems that global warming is causing.

10. What causes sea level to rise?
• There are two main causes of sea level rise
and both are due to heat. Glaciers and ice
sheets are large masses of ice that sit on the
land. As our planet warms, this ice melts and
flows into the oceans. More water in the
oceans makes sea level higher.
• Secondly, water expands as it gets warmer. So,
warm water takes up more room in our
oceans – making sea levels higher.

11. What causes sea level to rise?

12. How do we know sea level is rising?
• Unfortunately, you can't just put a long ruler into the ocean
to measure sea level rise. Sea level varies from place to
place. This is because of differences in geography, gravity,
temperature, ocean currents and tides.
• Oceans cover about 70 percent of the world. So, to know
how much sea level is rising all over planet, you'd have to
have millions of rulers in millions of different places.
• It turns out the best way to measure changes in sea level is
from space.

13. How do we know sea level is rising?

14. How do we know sea level is rising?

15. How do we know sea level is rising?
• NASA's Jason-3 satellite carries an instrument called a radar
altimeter. It uses radio waves instead of a ruler to measure
distances.
• Here's how it works. Jason-3 bounces radio waves off the
ocean surface. The satellite then times how long it takes for
these signals to return. Scientists can use this measurement
to calculate the distance between the satellite and the ocean
surface in that particular location.
• Jason-3 orbits about 800 miles (1,300 kilometers) above
Earth. Even from that far away, Jason-3 can measure the
distance from itself to the ocean surface to within about one
inch (about three centimeters).

16. How do we know sea level is rising?

17. Jason-3 also has instruments that allow
scientists to measure the distance from the
satellite to the center of Earth.

18. • By subtracting the first distance (between the
satellite and ocean surface) from the second
distance (between the satellite and Earth's
center), we can calculate the distance from
the ocean surface to Earth's center.

19. How do we know sea level is rising?
• The satellite constantly zips over new portions of
the planet. In about 10 days, it measures ocean
height over the entire Earth. Finding an average
of all those measurements gives an average sea
level for the whole planet.
• During the next 10 days, Jason-3 does it all over
again – and again and again, year after year! By
seeing how the average distance from the top of
the ocean to the center of the Earth increases
over time, we can measure how much and how
quickly sea level is rising.

20. Atmosphere
• Earth's atmosphere is a jacket of gases that
surrounds our planet. It keeps us warm, gives
us oxygen to breathe, and it is where our
weather happens.

21. Air is mostly gas.
• Air is all around us, but we can’t see it. So
what is air, exactly? It’s a mixture of different
gases. The air in Earth’s atmosphere is made
up of approximately 78 percent nitrogen and
21 percent oxygen. Air also has small amounts
of lots of other gases, too, such as carbon
dioxide, neon, and hydrogen.

22. An Ancient Find
• Around 4,000 years ago, someone in northern
China came across an odd black rock. It was
one of many. Then this person discovered
something. Somehow this person discovered
that the rock could burn.

23. • Life was harder back then. Keeping warm and
getting food were big worries. With no
electricity or gas for heating or cooking,
everyone burned wood. The strange rock that
burned like a log must have been very exciting
back then.
• This rock was coal. Archeologists think this
was the first time a human used a fossil fuel.

24. Slow to Pick up Steam
• For many years, only a few places with easy
access to coal used it. Outside China, one such
place was Britain. It was hard to miss there.
People could go to the beach and pick up lumps
of coal. They called it “sea coal.”
• During the years of Roman rule in the British
isles, they used coal to heat water for the public
baths. The Romans liked coal so much that they
brought it back to Rome with them. Traces of
British coal can be found all around the Roman
ruins in Italy.

25. • Before the late 1600s, coal was used mainly for things
like smelting and blacksmithing. (Smelting is a process
of heating the ore dug out of the earth to get out the
metals.)
• There were no real factories. Things were made by
hand without the help of machines. That all changed
with the invention of the steam engine.
• The first common steam engine was called the
Newcomen engine. It was first built 1712. It changed
the world forever. It was first used to drain mines, but
over time it was used for many other things too.

26. • The steam engine made big factories possible.
Then it was put into trains and ships, so it could
help transport things. It even powered some
early cars. The demand for coal skyrocketed.
• This big change was called the Industrial
Revolution. It began in Britain. It gradually spread
over much of the rest of the world. It’s not by
chance that Britain led the Industrial Revolution.
It had so much coal! It was this very coal that
drove Britain, and eventually the world, into the
modern society we know today.

27. What Can Trees Tell Us About Climate
Change?
• The characteristics of the rings inside a tree
can tell scientists how old a tree is and what
the weather conditions were like during each
year of that tree’s life. Very old trees can offer
clues about what the climate in an area was
like long before measurements were recorded.

28. What Can Trees Tell
Us About Climate
Change?

29. Quite a lot, actually!
• But to understand what the trees tell us, we first have to
understand the difference between weather and climate.
• Weather is a specific event—like a rain storm or hot day—that
happens over a short period of time. Weather can be tracked within
hours or days. Climate is the average weather conditions in a place
over a long period of time (30 years or more).
• Scientists at the National Weather Service have been keeping track
of weather in the United States since 1891. But trees can keep a
much longer record of Earth’s climate. In fact, trees can live for
hundreds—and sometimes even thousands—of years!
• One way that scientists use trees to learn about past climate is by
studying a tree’s rings. If you’ve ever seen a tree stump, you
probably noticed that the top of the stump had a series of rings. It
looks a bit like a bullseye.

31. • These rings can tell us how old the tree is, and
what the weather was like during each year of
the tree’s life. The light-colored rings
represent wood that grew in the spring and
early summer, while the dark rings represent
wood that grew in the late summer and fall.
One light ring plus one dark ring equals one
year of the tree’s life.

33. • Because trees are sensitive to local climate conditions,
such as rain and temperature, they give scientists some
information about that area’s local climate in the past.
For example, tree rings usually grow wider in warm,
wet years and they are thinner in years when it is cold
and dry. If the tree has experienced stressful
conditions, such as a drought, the tree might hardly
grow at all in those years.
• Scientists can compare modern trees with local
measurements of temperature and precipitation from
the nearest weather station. However, very old trees
can offer clues about what the climate was like long
before measurements were recorded.

34. • In most places, daily weather records have
only been kept for the past 100 to 150 years.
So, to learn about the climate hundreds to
thousands of years ago, scientists need to use
other sources, such as trees, corals, and ice
cores (layers of ice drilled out of a glacier).

35. How do we know Earth's climate is
changing?

36. How do we know Earth's climate is
changing?

37. • Extra greenhouse gases in our atmosphere are the
main reason that Earth is getting warmer. Greenhouse
gases, such as carbon dioxide (CO2) and methane, trap
the Sun's heat in Earth's atmosphere.
• It's normal for there to be some greenhouse gases in
our atmosphere. They help keep Earth warm enough to
live on. But too many greenhouse gases can cause too
much warming.
• The burning of fossil fuels like coal and oil increase the
amount of CO2 in our air. This happens because the
burning process combines carbon with oxygen in the
air to make CO2.
• It's important that we monitor CO2 levels, because too
much CO2 can cause too much warming on Earth.
Several NASA missions have instruments that study
CO2 in the atmosphere.

38. Why does it matter that Earth's
Climate is changing?
• We know what Earth's past climate was like by studying things that have
been around for a long time. For example, scientists can study what
Earth's climate was like hundreds of years ago by studying the insides
of trees that have been alive since then.
• But if scientists want to know what Earth's climate was like hundreds of
thousands to millions of years ago, they study sediment cores and ice
cores. Sediment cores come from the bottoms of lakes or the ocean floor.
Ice cores are drilled from deep — sometimes miles — below the surface of
the ice in places like Antarctica.
• A drilled ice core kind of looks like what you get if you plunge a drinking
straw into a slushy drink and pull it out with your finger over the end of
the straw.
• The layers in an ice core are frozen solid. These layers of ice give clues
about every year of Earth's history back to the time the deepest layer was
formed. The ice contains bubbles of the air from each year. Scientists
analyze the bubbles in each layer to see how mu

40. • Scientists can also use ice cores to learn about the
temperatures for each year. As snow accumulates onto a
growing glacier, the temperature of the air imprints onto
the water molecules in the ice.
• Scientists who use trees, ice cores, and lake and ocean
sediment to study Earth's climate are
called paleoclimatologists. They look at all of these sources
of information and compare their findings to see if they
match up. If they do, then their findings are accepted as
being most likely true. If the findings don't agree, the
scientists do more studies and collect more information.
• In the case of Earth's climate history, the results from many
different kinds of studies agree.

41. How can so little warming cause so
much melting?
• It takes a lot of energy to warm up water. However, the
oceans do absorb heat, and they do get warmer. This
warmer water causes sea ice to begin to melt in the
Arctic.
• Information from NASA's Earth satellites shows us that
every summer, some Arctic ice melts and shrinks,
getting smallest by September. Then, when winter
comes, the ice grows again. But since 1979, the
September ice has been getting smaller and smaller
and thinner and thinner. So, just a small amount of
warming can have a huge effect over several years.

42. • Glaciers are another form of melting,
shrinking ice. Glaciers are like frozen rivers.
They flow over land like rivers, only they move
much slower. Warmer temperatures cause
them to flow more quickly. Many of them flow
toward the ocean, breaking into huge chunks
that fall into the water.

43. What does sea level tell us about
climate change?
• More glaciers are melting into the ocean, and
the global sea level is rising. Sea level rise is
another clue that tells us Earth's climate is
getting warmer. But melting ice is not the only
cause of rising sea levels. As the ocean gets
warmer, the water actually expands! Scientists
have observed that the sea level has risen 7
inches in the last 100 years.

44. Note: The presentation uses material
from the Internet