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This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty.

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And I'm Pat Bodnar. This week: Reaction to Al Gore's movie about global warming ...

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And European astronomers find an unusual planetary system.

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Former Vice President Al Gore is starring in a new movie called "An Inconvenient Truth." It is a documentary about global warming. This is a subject that Mister Gore has been interested in for many years.

For the past six years, Mister Gore has been traveling around the country and the world giving talks about global warming. He has given the talks more than one thousand times. Most of "An Inconvenient Truth" is filmed at these events.

Mister Gore speaks to groups of people with a big screen behind him. Satellite pictures, scientific models, graphs and other images appear on the screen as he talks.

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The subject of global warming has been debated for years. Factories, power stations and vehicles produce carbon dioxide and other greenhouse gases. Greenhouse gases trap warm air in the atmosphere. Most climate scientists believe these gases are responsible, at least in part, for temperature increases on Earth. The debate centers on the extent to which greenhouse gases are responsible for global warming.

In the movie, Al Gore reports about the sharp increase in the amount of carbon dioxide in the atmosphere in the last fifty years. He compares countries around the world and their share of carbon dioxide releases. He also shows a similar increase in the Earth's temperature.

He shows melting glaciers and huge pieces of ice crashing into the ocean. He provides biological examples of global warming. He shows tropical animals, plants and diseases on the move northward as temperatures increase. And he shows a model of rising sea levels spreading over southern Florida, parts of India, Africa and other areas in the world. He also discusses the population explosion in the world and its increasing problems for the planet.

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Critics of the movie say Mister Gore is using the issue of global warming and his movie for a political campaign. They say he plans to run for president again. Mister Gore says he has no such plans.

Critics also say Mister Gore's warnings about what will happen if global warming continues are based more on guesswork than science. Richard Lindzen is a professor of Atmospheric Science at the Massachusetts Institute of Technology. He strongly criticized Mister Gore's movie in the Wall Street Journal newspaper.

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Mister Lindzen protested one of Mister Gore's major points of argument. The professor wrote it was wrong for Mister Gore to state that there is general agreement among scientists about global warming. For example, he argued that most evidence suggests that the Greenland ice sheet is growing, not shrinking.

He wrote that warming temperatures are not necessarily the cause of glacial melt. He wrote that glaciers retreat and advance unexpectedly and for reasons science cannot explain. He also wrote that the disease malaria was once common in the northern American state of Michigan and in Siberia.

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However, other scientists who saw the movie say Mister Gore's facts are generally right. The Associated Press said it had spoken to nineteen climate experts who saw the movie and generally approved of how the science was presented.

A new report also supports Mister Gore's movie. An independent group of scientists in the United States generally confirmed the findings of a major study on global warming from nineteen ninety-nine. The study had been disputed since its release.

A group of twelve scientists organized by the National Research Council now says they generally support the study's main finding. It found that the last few decades of the twentieth century were warmer than any comparable period in the last four hundred years.

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The United States Congress had asked the National Research Council to investigate the global warming study. The council is part of the leading scientific organization in the United States, the National Academies. It advises the American government and citizens about scientific issues.

Michael Mann was the climatologist who led the study that was examined. He was a professor at the University of Massachusetts at Amherst at the time.

The study was the first of its kind. It combined many different methods for estimating surface temperatures historically. These included examinations of rings on very old trees, studies of growth and loss of glaciers, cave research and many other methods. The evidence from all the sources was then organized to try to provide a whole picture of climate changes in the past one thousand years.

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The model of climate change it provided has been nicknamed "the hockey stick" after a stick used to play the sport of hockey. The graph shows a timeline at the bottom and atmospheric carbon dioxide levels on the side. The levels are mostly the same for hundreds of years but rise sharply toward the end of the timeline that represents the last hundred years or so.

Scientists at the American space agency, NASA, study climate change from direct temperature measurement. They report that two thousand five was the hottest year ever recorded.

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You are listening to SCIENCE IN THE NEWS in VOA Special English.

European astronomers have discovered a planetary system with at least three planets. These are all low mass and similar in size to Neptune in our own solar system. The planets orbit a star about forty-one light years from Earth. One light year is a distance of more than nine million million kilometers.

The star is named HD six-nine-eight-three-zero. It has a little less mass than our sun. It is part of the star group Puppis, the constellation known as the Stern.

The astronomers used a European Southern Observatory telescope in South America, at La Silla, in Chile. Their report appeared in Nature magazine. The lead writer was Christophe Lovis from the Geneva Observatory in Switzerland.

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They discovered the planets with an instrument called the High Accuracy Radial Velocity Planet Searcher, or HARPS. They did not see the planets. Instead, they used a system of indirect observation.

As the Planetary Society explains on its Web site, planetary.org, a star does not remain completely still when it is orbited by a planet. Instead, it moves in a very small circle in reaction to the gravitational pull of the planet.

So, planet hunters use a spectrograph to measure the movement of stars. Newer instruments can measure extremely small changes in speed. In this case, the HARPS spectrograph measured the movement of the star at between two and three meters a second.

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The radial velocity method has led to the discovery of almost all the planets found outside our solar system. Since nineteen ninety-five, scientists have found almost two hundred planets.

But this is the first planetary system where all the planets are similar in mass to Neptune. In other systems, at least one of the planets is the size of Jupiter, hundreds of times bigger than Earth.

In this one, the smallest planet is about ten times the mass of Earth. The largest is about eighteen times as big.

Something else also makes this planetary system interesting. Scientists recently found that the star could also have an asteroid belt. The main asteroid belt in our solar system orbits the sun between Mars and Jupiter. Asteroids are rocky objects thought to be left over from the formation of the universe.

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The three planets orbit the star in periods of nine days, thirty-two days and one hundred ninety-seven days.

The astronomers believe the planet closest to the star is rocky. The middle one is probably a mixture of rock and gas. And the one farthest away probably produced some ice during its formation. It is likely to have a rocky, icy center. The outer planet also orbits within the so-called habitable zone of the star. That means liquid water could exist at the surface.

Because of its heavy mass, however, this planet is probably not like Earth. The atmosphere is most likely hydrogen. Still, the astronomers say this newly found planetary system has a lot in common with our own.

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