What is "global climate change" ?

What is global climate change 

Is the climate of the whole Earth really changing?

Yes! Earth has been getting warmer—and fast.
Global climate is the average climate over the entire planet. And the reason scientists and folks 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.

What is climate?

"Climate" describes conditions over the long term and over an entire region.
Climate is the big picture. It is the big picture of temperatures, rainfall, wind and other conditions over a larger region and a longer time than weather. For example, theweather was rainy in Phoenix, Arizona, last week. But this city usually gets only 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, because it's warm and rains there a lot.

These two types of vegetation reflect their climates—one very wet and one very dry.

What is weather?

TV weather reporters need all the information they can get in order to predict the weather for just a few days.

Weather is local and temporary.
On our own Earth, 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's going to happen next.

It looks like this storm is getting ready to create a tornado.

Is that big black cloud going to let loose over San Francisco, or wait until it gets to Sacramento? Will that new storm forming in the Atlantic Ocean turn into a hurricane? Conditions are just right for tornadoes. Will any form? And where might they touch the ground and cause trouble?
Weather happens at a particular time and place. Rain, snow, wind, hurricanes, tornadoes—these are all weather events.

Do we care if Earth is getting warmer?

The whole Earth as seen from 22,300 miles away, out in space.

Yes, we care! After all, Earth is our spaceship.
It carries us on a 583-million-mile cruise around the Sun every year. It even has its own "force field." Earth has a magnetic field that protects us from killer radiation and brutal solar wind. For its life-support system, Earth has all the air, water, and food we need.
Just like astronauts on a long space voyage, we need to monitor all our "ship's" vital functions and keep our Earth "ship shape."

Earth is a magnificent spaceship. Its magnetic field is an "invisible force field" protecting us from the Sun's stormy blasts. And Earth gives us everything else we need to live.

Does what we do matter?

Earth's fate is in our hands.

Everything that happens here affects something over there.
Earth has its own control system. The oceans, the land, the air, the plants and animals, and the energy from the Sun all 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.

What is making Earth's climate warmer?

How can we take better care of our planet?

Scientists have discovered that humans are causing this warming.
But how do they know that? What are we doing that could cause the whole planet to get warmer? And how could warming happen so fast? What will happen to people and other living things if the planet keeps getting warmer? And what can we do to slow down or stop the warming?

How do we know the climate is changing ?

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. Earth is still beautiful.

Left to right: Virgin River in Zion National Park, Utah; dirt road through a dry valley in Onyx, California; Bryce Canyon National Park, Utah; polar bears in the Arctic.

So what is the problem? What is the fuss about climate change and global warming?
Well, after observing and making lots of measurements, using lots of NASA 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 long past.

All these satellites, plus a lot more, are studying Earth and all the changes happening with the air, ocean, land, and ice.

Polar bear clings to a small chunk of melting ice surrounded by open sea.

Global air temperatures near Earth's surface rose almost one and one-half 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. But when we are talking about the average over the whole Earth, lots of things start to change.

Why is Earth getting warmer?

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. And 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 CO2levels in the air are closely tied.

This graph shows carbon dioxide levels over the past 450,000 years. Notice the sharp increase starting around 1950.
Ref: http://www.ncdc.noaa.gov/paleo/globalwarming/temperature-change.html.)

This graph shows CO2 levels over the past 450,000 years. As you can see, for 450,000 years, CO2 went up and down. But CO2 levels never rose over 280 parts per million until 1950. But then something different happens and CO2 increases very fast. At the end of 2012, it is 394 parts per million*. Why?
Because of us and our fossil fuels.
Now, let's look at that graph again, but adding the temperatures for that same period of Earth's history.

This graph shows how carbon dioxide and temperature have risen and fallen together in Antarctica over the past 400,000 years.
Ref: http://www.epa.gov/climatechange/science/pastcc_fig1.html.

You can see how CO2 levels change with temperature. Look at what it is doing now.
Yipes!

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* Reference NOAA's Earth system Research Laboratory, Global Monitoring Division, http://www.esrl.noaa.gov/gmd/ccgg/trends.

How do we know what Earth was like long ago?

A big part of the answer is 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. It's 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. 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 can also 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.)

(Clockwise from top left) Ice coring machine, hole in ice, pulling ice core from machine, man with hands on ice core tube in ground, scientist holding up ice core in triumph, man hand drilling ice core.

Other scientists study cores of sediment from the bottom of the ocean or lakes. Or they 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. If they do, then their findings are accepted as most likely true. If they don't agree, they go back and figure out what is wrong with their methods.

Left to right: Scientist kneels next to a tree core showing its many years of rings; cross-cut tree trunk showing its rings; scientist studies tree specimen with microscope and other instruments.

In the case of Earth's climate history, the facts agree from a lot of different kinds of studies.

How can so little warming cause so much melting?

Water can soak up a lot of heat. When the oceans get warmer, sea ice begins to melt in the Arctic and around Greenland. NASA's Earth satellites show 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. Check out the Climate Time Machine and watch the ice shrink.

Earth's Arctic area: On left, the ice cap covers a large part of the Arctic Ocean. this image is an average of the ice extent during Septembers of 1979-1981. On right, however, a much smaller area is covered by ice in September 2007.
Ref: http://www.nasa.gov/topics/earth/sea_ice_nsidc.html.

See how much three glaciers have shrunk over time. Columbia Glacier from 1980 - 2005; Arapaho Glacier from 1898 to 2003; and Grinnell Glacier from 1940 - 2006.

Glaciers are another form of melting, shrinking ice. Glaciers are frozen rivers. They flow like rivers, only much slower. Lately, they have been speeding up. Many of them flow toward the ocean, then break off in chunks--sometimes huge chunks. In places such as Glacier National Park, the glaciers are melting and disappearing. The air is getting warmer, and less snow is falling during winter to renew the melted parts of the glaciers.

Doesn't rising sea level just bring us closer to the beach?

As more sea ice and glaciers melt, the global sea level rises. But melting ice is not the only cause of rising sea level. As the ocean gets warmer, the water actually expands! Sea level has risen 6.7 inches in the last 100 years. In the last 10 years, it has risen twice as fast as in the previous 90 years. If Greenland's ice sheet were to melt completely, sea level all over the world would rise by 16-23 feet (5 to 7 meters). The map above of the southeastern U.S. shows in red the area that would be under water if sea level were to rise by 20 feet (6 meters).
Double yipes!

Play with the Climate Time Machine to see what rising sea level will do to other parts of the world.

How does climate change affect other species?

Life is a web, with every strand connected to every other strand. One species of plant or animal changes, and a whole chain of events can follow involving many other species.

This caribou mom looks a little thin. Photo: Al Seib/Los Angeles Times.

For example, herds of caribou live in cold, Arctic locations. Caribou hate mosquitoes. In the past few years, warmer temperatures in summer have allowed mosquito populations to explode. So the caribou spend a lot more energy swatting away the mosquitoes. All this swatting leaves the caribou less energy to find food and prepare for the next long winter. Female caribou are especially troubled because it takes so much energy to give birth and raise their young.

This marmot may have awakened from his winter nap too early, but he still seems to be getting plenty to eat.

Animals that hibernate in the winter also suffer from warming temperatures. Marmots, chipmunks, and bears are waking up as much as a month early. Some are not hibernating at all. These animals can starve if they stay awake all winter, because they can't find enough food. If they wake up too early because it feels warm enough to be spring, the days may not yet be long enough to signal the plants to start their spring growth. So, again, the wakeful animals go hungry.
Many trees in the Western U.S. are already suffering from climate change. Droughts leave trees thirsty and stressed. Pine trees need cold winters, too. With warmer, drier conditions, the trees are more likely to become infected with insects. These bugs bore into the trees and lay their eggs. Eventually, they kill the tree. Some forests in the West have lost over half their trees already to pine beetles. When the forest is gone, birds and small mammals that lived there have to find new homes--if they can.

This forest is infected with pine beetles. The close-up is the inside of a tree infected with the beetles.

There are many more plant and animal species and communities struggling to adapt to the rapidly changing climate.

September 2009 Station Fire near Los Angeles.

This satellite image shows the "Station Fire" of September 2009, which burned one-fourth of the Angeles National Forest (near Los Angeles). In the future, drought conditions and record hot temperatures could make fires like this more frequent and intense.

Source: http://climatekids.nasa.gov/