Mountaineers have noted that as they climb, for example, up to the 12,633­foot Humphreys Peak in Arizona, plant life changes greatly. In the Sonoran Desert, one climbs into a pine forest at 7,000 feet and a treeless tundra(冻土带) on the top of the mountain. It may seem that plants at a given altitude are associated in what can be called “communities” －groupings of species. The idea is that over time, plants that require particular climate and soil conditions come to live in the same places, and are frequently to be found together. Scientists study the history of plant life and build up a picture of how groups of plants have responded to climate changes and how ecosystems develop. But are these associations, which are real in the present, permanent?

    A great natural experiment took place on this planet between 25,000 and 10,000 years ago, when small changes in the earth's orbit caused great sheets of ice to spread from poles. These glaciers(冰川) covered much of North America and Europe to depths of up to two miles, and then, as the climate warmed, they retreated. During this retreat, they left behind newly uncovered land for living things to occupy, and as those living things moved in they laid down a record we can read now. As the ice retreated and plants started to grow near a lake, they release pollen(花粉). Some would fall into the lake, sink to the bottom and mix with the sand. By drilling into the lake bottom it is possible to read the record of the plant life around the lake. The fossil record seems clear; there is little or no evidence that entire groups of plants moved north together. Things that lived together in the past don't live together now, and things that live together now didn't live together in the past. Each individual living things moved at its own pace. The fossil record seems to be telling us that we should be thinking about preserving species by giving them room to move about－to respond to environmental changes.

    When I was 16 years old, I made my first visit to the United States. It wasn't the first time I had been abroad. Like most English children I learned French at school and I had often been to France, so I was used to speaking a foreign language to people who didn't understand English. But when I went to America I was really looking forward to having a nice easy holiday without any language problems.

    How wrong I was! The misunderstanding began at the airport. I was looking for a public telephone to give my American friend Danny a ring and tell her that I had arrived. A friendly old man saw me looking like being lost and asked if he could help me.

    “Yes,” I said. “I want to give my friend a ring.”

    “Well, that's nice,” he said. “Are you getting married? But aren't you a bit young?”

    “Who is talking about marriage?” I replied. “I just want to give my friend a ring to tell her I've arrived. Can you tell me where there's a phone box?”

    “Oh!” he said. “There's a phone downstairs.”

    When at last we did meet up, Danny explained the misunderstanding to me.

    “Don't worry,” she said to me. “I had many difficulties at first. There are lots of words which the Americans use differently in meaning from us British. You'll soon get used to all the funny things they say. But most of the time British and American people can understand each other!”

    The Maldives faces the threat of extinction from rising sea levels, but the government said on Thursday it was looking to the future with plans to build homes and a golf course that can float.

An increase in sea levels of just 18 to 59 centimeters would make the Maldives — a nation of a number of tiny coral islands in the Indian Ocean — not suitable for humans to live in by 2100, the UN's climate change experts have warned.

    President Mohamed Nasheed has declared a fight for survival, and last month he signed a deal with a Dutch company to study suggestions for a floating structure that could support a conference centre, homes and an 18-hole golf course.

    The company, Dutch Docklands, is currently building floating developments in the Netherlands and Dubai. Its website said it undertook projects that make “land from water by providing large-scale floating constructions to create similar conditions as on land”.

    The Maldives began to work on an artificial island known as the Hulhumale near the crowded capital island of Male in 1997 and more than 30,000 people have been settled there in order to ease crowdedness. The city, which has a population of 100,000, is already protected from rising sea levels by a 30-million-dollar sea wall, and the government is considering increasingly imaginative ways to fight climate change.

    Nasheed, who held the world's first underwater cabinet (内阁) meeting in October to highlight his people's serious and difficult situation, has even spoken of buying land elsewhere in the world to enable Maldivians to relocate if their homes are completely covered.

    He has also promised to turn his nation into a model for the rest of the world by becoming “carbon neutral (碳中和)” by 2020. His plan involves ending fossil fuel use and powering all vehicles and buildings from “green” sources such as burning coconut husks.

    Antarctica(南极洲)'s melting ice, which has caused global sea levels to rise by at least 13.8 millimeters over the past 40 years, was thought to primarily come from the unstable West Antarctic Ice Sheet(WAIS). Now, scientists have found that the East Antarctic Ice Sheet (EAIS)—considered largely unaffected by climate change—may also be melting at an unexpectedly rapid speed.

    The WAIS, whose base is below sea level, has long been considered the most likely to break down. Besides gravity, a deep current of warm water slips beneath the sheet, melting it from below until it becomes a floating shelf at risk of breaking away. In contrast, extreme cold and a base mostly above sea level are thought to keep the EAIS relatively safe from warm waters.

    But as greenhouse gases warm much of the planet, driving stronger polar winds, some scientists think warm water carried by a circular current will start to invade East Antarctica's once unassailable ice. A cooperation of more than 60 scientists last year, published in Nature, estimated that the EAIS actually added about 5 billion tons of ice each year from 1992 to 2017.

    Eric Rignot of the University of California, Irvine, and colleagues combined 40 years of satellite imagery and climate modeling and found that overall Antarctica now sends six times more ice into the sea each year than it did in 1979, with the majority coming from West Antarctica. But East Antarctica was responsible for more than 30% of Antarctica's contribution to the 13.8-millimeter sea level rise over the past 40 years. “The more we look at this system the more we realize this is fragile,” Rignot says. “Once these glaciers become unstable there is no red button to press to stop it.”

    Rignot hopes the study brings greater attention to a part of Antarctica that has traditionally been understudied. Helen Fricker, a glaciologist (冰川学家) in California, agrees. “We need to monitor the entire Antarctica and we just can't do that without international cooperation.”

Time Travel

    If you could travel in time, where would you go? Perhaps you would watch an original performance of a Shakespeare's play in Elizabethan England? What about hanging out with Laozi in the Spring and Autumn Period? Or maybe you'd voyage far ahead of the present day to see what the future holds.

    The possibility of time travel is indeed appealing. Stories exploring the subject have been around for hundreds of years. Perhaps the best known example is science fiction novel. The Time Machine, which was written by H.G. Wells and published in 1895 for the first time. It was adapted into at least two feature films of the same name, as well as two television versions, and a large number of comic book adaptations. It is generally credited with the popularization of the concept of time travel using a vehicle that allows an operator to travel purposefully and selectively. The term "time machine", coined by Wells, is now universally used to refer to a vehicle transporting people into the far future.

    But could time travel actually be possible? Some scientists say yes, in theory. They propose using cracks in time and space called “wormholes”, which could be used as shortcuts to other periods. Einstein's theory of relativity allows time travel in extreme circumstances. And British physicist Stephen Hawking says you could travel into the future with a really fast spaceship going at nearly the speed of light. Though building such a spaceship would of course be no simple task.

    Even if you could travel into the past, there is something called the “grandfather paradox”. It asks what would happen if a time traveler were to go back in time and have his own grandfather killed for some reason, and therefore prevent himself from being born. If the time traveler wasn't born, how would he travel back in time?

    And would you really like to visit the future? In H.G. Wells' book, the main character travels into distant time where he arrives at a beach and is attacked by giant crabs. He then voyages 30 million years into the future where the only living thing is a black object with tentacles(触角).

    If that's what's in store, maybe we are better just living in the present day after all.

    New study shows that when teachers participate in a training program focused on prosocial (亲社会的) classroom behavior, their students are better able to control their emotions, and that children who can regulate emotions are more likely to be academically successful.

    For the study, which appears in Prevention Science, researchers looked at more than 100 teachers and 1,817 students from kindergarten to third grade to see if teachers could support students' emotional and behavioral growth through the Incredible Years Teacher Classroom Management (IYTCM) program.

    The program uses videos and training sessions, along with role-playing and coaching, to help teachers learn management skills such as using behavior-specific praise, building positive relationships with students, and considering how to reduce poor behavior. Teachers in the training group increased interactions with students by 64 percent compared with 53 percent for teachers in the control group without the training.

    "Emotional regulation is the ability to recognize what behavior is appropriate in the present situation," says Wendy Reinke, professor in the College of Education at the University of Missouri. "For example, a student might have difficulty controlling the feeling of anger if he or she becomes annoyed with another student. But under this program, the teacher encourages them to move to a different spot in the classroom, effectively teaching them that sometimes stepping away and taking a break is a good way to calm down and manage8ha8feeling."

    After one school year of using the program in classrooms, students improved their social ability and ability to regulate their emotions. These improvements resulted in an increase in the tests for students in Incredible Years classrooms vs. students in control classrooms. And this classroom management approach can help reduce the risk for struggling learners early on, which could help prevent more accumulative support needs in a child's future.