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Introduction Climate Tracker Inez Fung loves a mystery. The mystery in front of her right now is how Earth's climate is changing--and why. Earth is warming up, and strange things are happening. Glaciers that have been around for thousands of years are melting. Sea levels are slowly rising. In some parts of the world, less snow is falling in winter and spring flowers are budding earlier. In others, severe storms are more common. Are all of these events connected? If so, what's happening to Earth's climate to cause them? And what other disturbing climate events lie on the horizon? These are questions Inez wants to answer. It's hard to predict the future, but Inez's job is to try. Her tools are equations, mathematical models, and superfast computers. To understand how climate works and how it might change, she simulates Earth's natural processes--such as winds, ocean currents, precipitation, and cloud formations--inside her computer. She can change any of these variables, and then witness what could happen to climate in the next 50, 100, or even 500 years! There's nothing about the way Earth works that doesn't fascinate Inez. She's always asking new questions and searching for new puzzles to solve. Along the way, she's helping us better understand what the future of Earth's climate might hold. ix

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Inez Fung has done much of herwork in the United States, as a NASA scientist. But herjourney started halfway around the world in Hong Kong.

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1 MEET INEZ FUNG I nez Fung loves science fiction movies. In the summer of 2004, she rushed to the theater to see a movie that promised a look at the future. It was a future when Earth's climate had gone haywire, causing worldwide disaster. On an outing in Climate is the average weather in a place occuring over Oregon, Inez Fung decades or even centuries. But the movie showed a lightning- pauses beside a lake near the base of quick climate change. Sea surface temperatures in the northern Mount Hood (oppo- hemisphere dropped overnight. Ocean currents reversed site). Inez has learned direction. Huge waves crashed through the streets of New York that everything in nature--from forests City, sweeping away buses, cars, and people. Then a deep freeze and oceans to snow hit. Thick layers of snow and ice covered entire buildings. and clouds (above)-- Inez watched the movie with keen interest. After all, it was a affects climate. She is also finding that what movie about future climate change--her science specialty. But she people do can affect wasn't impressed. The special effects were good, but the science the climate, too. was bad. First of all, climate change would never happen as fast as it did in the movie, nor in the way it was shown. Second, she says with a laugh, "When I looked at the storm system they showed on the computer screen, the parcels of air were moving in the wrong direction." Oops! Movie producers, take note. If you're going to make a science fiction movie, get the science right--or hope that scientists like Inez Fung don't go to see it. 1

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~Science TH Fact or Fiction? EAR Bad science or not, science fiction writers love to show a future where the Earth we know has been ruined by extreme climate change. There have been desert wastelands. One movie even FORECAST showed a watery world where oceans had swallowed up the land. These views of the future are fantasy. But climate change is not. Earth's climate has shifted many times during the planet's 5-billion-year history. During the ice ages, thick sheets of ice covered large parts of Earth's land surface. But ice ages were part of Earth's natural climate cycles--they happen periodically. The Earth cools. Ice sheets form and spread. Then the ice age ends and Earth has a warmer period, like the one we're enjoying now. But is something throwing off these natural cycles? Scientists see evidence of climate extremes that have never been seen before. The problem now, however, is the opposite of a deep freeze. The 20th century was the Carbon dioxide is warmest in the past 1,000 years. produced naturally, And 9 of the 10 warmest but human activitiy has greatly increased years in the last 150 have the amount of this gas occurred since 1990. in Earth's atmosphere. Droughts (long dry Vehicles alone produce almost one-fourth of spells) are more severe the carbon dioxide in some areas and released into the air. snowfall has declined in others, which is a kind of drought in winter. Some trees are budding earlier in the spring. And several plant species have even started to grow in places that were once too cold for them. Climate scientists are looking at this data and asking, "Why?" Will natural cycles bring the deep freeze of an ice age back again? Or have human actions changed the cycles of climate forever? 2

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Inez Fung is one of the scientists asking the questions. She is a Sunlight reacts with air pollution to create climate scientist. Her job is to study what determines climate, as a cloud of smog well as how and why climate changes over long periods of time. around cities such as The data that scientists are seeing points to people as the main Los Angeles. Some compounds in smog, culprits behind the climate change. We drive cars and trucks. We such as ozone, are use electricity to run everything from computers to air conditioners. greenhouse gases. Our factories turn out the many products we use every day. All of these activities require the burning of fossil fuels. These are fuels such as coal, oil, and natural gas. They formed from living organisms that died millions of years ago, so they all contain carbon. As fossil fuels burn, they give off carbon dioxide as a by- product--and that's the problem. Carbon dioxide is a greenhouse gas--a gas that helps trap heat in Earth's atmosphere. (See box, pages 4-5.) Since the widespread use of the coal-burning steam engine began in the early 1800s, we've been burning an increasing amount of fossil fuel. Carbon dioxide has continued to build up in the air, and so have other greenhouse gases. The concentration of carbon dioxide in Earth's atmosphere is MEET INEZ FUNG 3

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TH now the highest it has been in more than 400,000 years. The added carbon dioxide has also made Earth's average temperature climb. EAR During the past century, it has risen an average of about 1F. Warming in some areas is much higher. Climate scientists such as Inez are already seeing the effects of this change. Arctic sea ice has thinned. Mountain glaciers have FORECAST What Is the Greenhouse Effect? Earth would be a frozen wasteland if not alone is not what keeps Earth warm. In for the greenhouse effect--the process addition, heat from Earth's surface gets that keeps Earth's lower atmosphere warm trapped and held in place by the enough to make life on the planet possible. atmosphere. A similar process is at work Without it, Earth's average surface when a sleeping bag traps your body heat temperature would be about 54F colder and keeps you warm on a frosty night. than it is now. So how does the greenhouse effect work? You can often feel the warmth of the Sun To understand, you have to know about on your skin. But direct heat from the Sun electromagnetic radiation--the form in which solar energy reaches Earth. This A portion of the Sun's radiation (yellow arrow) radiation streaks through space in invisible passes through the atmosphere and reaches Earth. Some of that radiation is absorbed, heating Earth's waves that move at the speed of light. The surface. Infrared radiation (red arrows), or heat, is distance from the crest of one wave to the emitted back into the atmosphere. That energy crest of the next is called the wavelength of causes molecules of greenhouse gases to vibrate the radiation. Wavelengths range from and produce heat of their own, warming the millionths of an inch for very high energy lower atmosphere and Earth's surface. gamma rays to several miles for the longest, lowest energy radio waves. The Sun emits mostly high- energy shortwave radiation. This includes the light we see, or visible light. It also includes ultraviolet radiation--the invisible energy that can give you a sunburn even on a cloudy day. Few substances in Earth's upper atmosphere have the molecular 4

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shrunk. Four fifths of the glaciers in Montana's Glacier National Park have disappeared in the past 100 years. The loss of land ice and the warming of oceans have caused a slow but steady rise in sea levels. The number of days with frost has also decreased over most areas of the Earth. Inez and her fellow climate scientists are doing research to Radio Microwave Infrared Visible Ultraviolet X-ray Gamma ray structure to absorb shortwave radiation. Electromagnetic radiation ranges from radio So about half of this radiation passes waves that are miles long to gamma rays that right through and strikes the planet's are only millionths of an inch in length. Visible light ranges from red (longest) to surface. Earth's surface does absorb violet (shortest) light. When we see all shortwave radiation, but then emits it at wavelengths of visible light together, as in a different wavelength. Because Earth's sunlight, we see white light. surface temperature is much lower than that of the Sun--only about 60F compared to the Why is this called the Sun's 11,000F--the surface greenhouse effect? Because emits mostly lower-energy a similar principle warms a longwave radiation, or glass greenhouse (left). infrared radiation, into the Shortwave solar energy atmosphere. easily passes through Greenhouse gases such as the glass panes of a carbon dioxide and methane greenhouse, just as it passes don't just let longwave radiation through Earth's atmosphere. The zip by them. The radiation excites the inside of the greenhouse absorbs this molecules of these gases, making them solar radiation, then emits much of it as vibrate more rapidly and produce heat heat. This time, however, the glass traps of their own. This heat warms Earth's much of the heat inside the greenhouse, lower atmosphere as well as the planet's just as greenhouse gases trap heat in surface. Earth's atmosphere. MEET INEZ FUNG 5

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The warming TH climate is affecting glaciers. In 1850 EAR Glacier National Park had 150 glaciers. Now it has about 50. Sperry Glacier has shrunk between 1907 FORECAST (right) and 2001 (below). If warming continues, Glacier National Park could have no glaciers by 2030. understand these changes. They have some important questions to answer. Will Earth continue to get warmer? If so, how much and how fast? What is causing the warming? How will a warmer Earth differ from the Earth we know now--and how will it affect us? No one expects the world to turn into a desert anytime soon. But there could still be serious consequences. Climate scientists say that big changes are possible in the future based on the warming they predict now. For example, climate zones could shift, keeping some plants or animals from living where they do at present. Imagine palm trees in New York! Or the North Pole with no polar bears! If large parts of the polar ice caps were to melt, as some scientists predict they could, sea levels could rise several feet. Low coastal areas, where many people live, could end up underwater. 6

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Islands such as the Maldives--where the highest point is just eight feet above sea level--could disappear beneath the Indian Ocean. Important ocean currents that carry warm water from equatorial regions toward the poles, such as the Gulf Stream, could weaken, cooling some regions around the North Atlantic Ocean. What Are Greenhouse Gases? Greenhouse gases are the atmospheric gases that contribute most to the greenhouse effect. More than any others, these gases absorb the heat that Earth radiates. They in turn re-radiate their energy to Earth, thus warming its surface and lower atmosphere. Without greenhouse gases, Earth's heat would escape into space. Greenhouse Gas Natural Sources Human Sources Carbon Dioxide Decay of plants, respiration Burning of fossil fuels (coal, oil, gas) in living organisms, volcanic in electric power plants and motor eruptions, oceans vehicles, burning wood, cutting trees and other plants that remove carbon dioxide from the atmosphere Methane Wetlands (swamps, Rice farming, cattle raising, decay of marshes, bogs), stomachs garbage in landfills, coal mining, of cattle and termites leaks from natural gas pipelines Nitrous Oxide Livestock waste, wetlands Burning of fossil fuels in electric power plants and motor vehicles, fertilizers Ozone Reaction of ultraviolet Reaction of sunlight with air radiation from the Sun pollutants (often from motor with oxygen in the upper vehicles) in lower atmosphere atmosphere. Release from containing carbon and nitrogen. plants and trees in the Major part of smog. lower atmosphere. Chlorofluorocarbons None. This is an artificial Coolant in air conditioners and (CFCs) chemical made in the refrigerators, used in fire extinguishers, laboratory. in making plastic foam, and as a propellant in spray cans Water Vapor Evaporation from Earth's surface MEET INEZ FUNG 7

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~Foretelling TH the Future EAR Inez's job involves trying to forecast a future where climate could be much different than it is today. She studies climate patterns of the past and present. She examines the many factors that are part FORECAST of the climate, including ocean surface temperatures and currents, winds, and the amount of greenhouse gases and dust in the atmosphere. Then she tries to figure out what will happen to the climate if those factors change--as well as what happens to those factors as climate shifts. The way Inez does her research is pretty amazing. She can't use the entire planet for her experiments. There's no way to make the winds or ocean currents act a certain way so she can see how they affect the carbon dioxide in the air. Instead Inez re-creates Earth--and several of its atmospheric, oceanic, and terrestrial (land-based) systems--inside a computer as a model. Inez calls this global model her own "curious little world." She gives that virtual world characteristics that closely match those on Earth. Then she sets the model in motion and waits to see what happens. The idea is to understand natural climate cycles, then find out how the things that people do affect those cycles. What happens to Earth's climate, for example, as people produce more carbon dioxide or other greenhouse gases? Why does Inez do this? "First of all," she says, "it's a giant puzzle. But it's also important. The climate changes of the past 100 years have been small; they're comparable to natural changes. During the next 100 years, though, we don't expect the changes to be that small." Many computer models predict that the effects of a warmer Earth could be drastic in some areas. There could be many more scorching-hot days. There could be severe drought in areas that are already semidry and more drenching rain in areas that are already wet. Severe storms, such as the intense hurricanes that hit Florida one after the other in the summer and fall of 2004, could become more frequent. 8

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So Inez tries to describe what she knows to the people who make decisions that could affect climate. She can only provide the scientific understanding and computer projections. If we're lucky, decision- makers--such as government officials and business leaders--will take note. Then they will use the knowledge to prevent some of the more damaging changes from happening. Inez has been studying climate with computer models for more than 20 years. She has made important contributions to improving them. Her discoveries have Growing up in Hong helped scientists learn more about what influences climate, and Kong, Inez (above) much preferred the how climate could change. Along the way she has won many blue sky and open awards for her research. sea of the coast to Inez Fung has done much of her work in the United States, as the city's crowded streets (top). a NASA scientist. But her journey started halfway around the world in Hong Kong, where as a young girl she loved to swim in the ocean and watch clouds in the sky. Back then no one could have predicted how far she would travel or the terrific things she would do. MEET INEZ FUNG 9