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Climate Change
Vista de la Tierra desde el espacio

This photograph of Earth was taken in space by a NASA astronaut. Image Credit: NASA
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What does global climate change mean?

Earth is truly our spaceship.

Did you think NASA was all about astronauts, space shuttles and missions to Mars? NASA is all of those and much more. It is also about the most important planet to us -- Earth.

Earth is our spaceship. Just like astronauts on a long space voyage, we need to monitor all our ship's vital functions and keep our Earth in good condition.

Weather is local and temporary.

Instead of air conditioning, Earth has weather. However, we cannot control weather by turning a thermostat up to make it warmer or down to make it cooler. The best we can do is try to predict the weather. Weather scientists, called meteorologists, try to foresee what is going to happen next.

Weather happens at a particular time and place.

Rain, snow, wind, hurricanes, tornadoes -- these are all weather events.

Una imagen satelital muestra al huracan Earl en la costa de Carolina del Norte

A satellite image shows Hurricane Earl along the North Carolina coast. Image Credit: NASA
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Climate is regional and long-term.

Climate is the bigger picture. It is the broad picture of temperatures, rainfall, wind and other conditions over a larger region and a longer time. For example, the weather might be rainy in Phoenix, Ariz. This city usually gets about 7 inches of rain each year, so the climate for Arizona is dry. Much of Southern California also has a dry, desert climate. Brazil has a tropical climate. It is warm and very rainy.

Whatever happens in Earth's climate system affects everything else?

Even though Earth has no thermostat, it has its own control system. The oceans, the land, the air, the plants and animals, and the energy from the sun affect each other to make everything work in harmony. Nothing changes in one place without changing something in another place. The overall effect gives us our global climate.

Earth has been getting warmer -- and fast.

Global climate is the average climate over the entire planet. The reason scientists and people like you are concerned is that Earth's global climate is changing. The planet is warming up fast -- faster than at any time scientists know about from their studies of Earth's entire history. Scientists have discovered that humans are causing this warming.

La particion del glaciar Jakobshavn desde 1850 hasta 2006

This image of the Jakobshavn glacier on July 7, 2001, shows the changes in the glacier's calving front between 1851 and 2006. Historic calving front locations, 1850 through 1964, were compiled by Anker Weidick and Ole Bennike and are shown here in gray. Recent calving front locations, 2001 through 2006, derived from satellite imagery are shown in colors. A distance scale is provided. Image Credit: NASA
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So what if Earth gets a tiny bit warmer?

The sky is still blue. Trees are still green. Wind still blows. Clouds are still white and fluffy. Rain still pours from the sky. Snow falls, and it still gets really cold sometimes in some places.

So what is the problem? What is the fuss about climate change and global warming?

After observing and making lots of measurements, after using lots of satellites and special instruments, scientists see some alarming changes. These changes are happening fast -- much faster than these kinds of changes have happened in Earth's history.

Global air temperatures near Earth's surface rose almost 1.5 degrees Fahrenheit in the last century. Eleven of the last 12 years have been the warmest on record. Earth has warmed twice as fast in the last 50 years as in the 50 years before that.

One and one-half degrees may not seem like much. However, when we are talking about the average increase over the whole Earth, lots of things start to change.

Why is Earth getting warmer, and what does carbon have to do with it?

Why is Earth getting warmer? Here's one clue: As the temperature goes up, the amount of carbon dioxide, or CO2, in the air goes up. As the carbon dioxide goes up, the temperature goes up even more.

Carbon dioxide is a greenhouse gas. That means it traps heat from Earth's surface and holds the heat in the atmosphere. Scientists have learned that, throughout Earth's history, temperature and CO2 levels in the air are closely tied. For 450,000 years, CO2 levels have gone up and down. But CO2 levels never rose over 280 parts per million until 1950. Then something different happened, and CO2 increased very fast. In 2009, CO2 levels reached 388 parts per million. Why? Humans are affecting the climate.

Foto montaje de nucleos de hielo y perforacion de hielo

Ice sheets contain a record of hundreds of thousands of years of past climate, trapped in the ancient snow. Scientists recover this climate history by drilling cores in the ice, some of them over 3,500 meters (11,000 feet) deep. These photographs show experimental drilling on the Greenland Ice Cap in summer 2005. Photographs copyright Reto Stöckli, NASA GSFC
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How do scientists know what Earth was like half a million years ago?

They study ice cores.

In Antarctica, scientists have drilled down two miles below the surface and brought up samples of the ice. These samples are called ice cores. An ice core is similar to 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. What you will have inside the straw is an ice core, although a very slushy one.

The layers in an Arctic ice core are frozen solid. They 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 much CO2 they contain. Scientists also can learn about the temperatures for each year by measuring relative amounts of different types of oxygen atoms in the water. Remember, water is H2O: two hydrogen atoms and one oxygen atom.

Other scientists study cores of sediment from the bottom of the ocean or lakes. Some study tree rings and layers of rocks to give them clues about climate change throughout history. They compare all their findings to see if they agree. In the case of Earth's climate history, scientists have reached similar conclusions from their studies.

Las satelites de la NASA que observan la Tierra

NASA currently has more than a dozen Earth science spacecraft/instruments in orbit studying all aspects of the Earth system (oceans, land, atmosphere, biosphere, cyrosphere), with several more planned for launch in the next few years. Image Credit: NASA
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Can NASA help to answer all scientists' questions?

NASA has more than a dozen satellites studying Earth. Many of these satellites carry several science instruments and study more than one question. The information these satellites gather will help climate scientists understand Earth and answer hard questions like: Do clouds and aerosols make Earth warmer or cooler? How much of the CO2 that humans produce can Earth clean out of the air? How will climate change affect where it rains and snows? How high and how fast will sea level rise?


Adapted from: http://climate.nasa.gov/kids/bigQuestions/whatDoesGCCmean