|Global warming (National Geographic)|
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A short documentary from National Geographic explaining what global warming is and alerting about its consequences.
For 2.5 million years, the earth’s climate has fluctuated, cycling from ice ages to warmer periods. But in the last century, the planet’s temperature has risen unusually fast – about 1.2 to 1.4 degrees Fahrenheit. Scientists believe it’s human activity that’s driving the temperatures up; a process known as global warming.
Ever since the industrial revolution began, factories, power plants, and eventually, cars, have burned fossil fuels such as oil and coal, releasing huge amounts of carbon dioxide and other gases into the atmosphere. These greenhouse gases trap heat near the earth through a naturally occurring process called the greenhouse effect.
The greenhouse effect begins with the sun and the energy it radiates to the earth. The earth and the atmosphere absorb some of this energy, while the rest is radiated back into space. Naturally occurring gases in the atmosphere trap some of this energy and reflect it back, warming the earth. Scientists now believe that the greenhouse effect is being intensified by the extra greenhouse gases that humans have released.
Evidence for global warming includes a recent string of very warm years. Scientists report that 1998 was the warmest year in measured history, with 2005 coming in second. Meanwhile, readings taken from ice cores show that the greenhouse gases, carbon dioxide and methane have hit their highest levels in the past 420,000 years. Arctic sea ice is also shrinking. According to NASA studies, the extent of Arctic sea ice has declined about 10% in the last 30 years.
As long as industrialized nations consume energy and developing countries increase their fossil fuel consumption the concentration of greenhouse gases in the atmosphere will continue to rise. Researchers predict that temperatures will increase about 2 to10 degrees Fahrenheit by the end of the century. What’s less certain is what rising temperatures mean for the planet.
Some climate models predict subtle changes. Others forecast rising sea levels which could flood coastal areas around the world. Weather patterns could change, making hurricanes more frequent. Severe droughts could become more common in warm areas and species unable to adapt to the changing conditions would face extinction.
Although much remains to be learned about global warming, many organizations advocate cutting greenhouse gas emissions to reduce the impact of global warming.
Consumers can help. By saving energy around the house, switching to compact fluorescent light bulbs and driving fewer miles in the car each week. These simple changes may help keep the Earth cooler in the future.
CYCLING= Moving in cycles, changing in a way that it goes through the same stages again and again, as in circles.
ICE AGE= A period in geological history when a big part of the planet was covered with ice.
POWER PLANTS= Factories where electricity is produced.
FOSSIL FUELS= Crude oil and coal. This kind of fuel is called "fossil" because it comes from biological material (animals and plants) that was transformed into a stone (coal) or a liquid (oil) over thousands of years.
SUCH AS= for example...
RELEASING= Liberating, letting go.
HUGE= Very big, immense.
GREENHOUSE= A room made of glass where plants can grow in a warm atmosphere even if it’s cold outside. A greenhouse gas is a gas that causes our planet to function in the same way as a greenhouse, letting the sun heat in and trapping it inside, so the temperature is higher than it should.
THE EARTH AND THE ATMOSPHERE ABSORB...= We say "absorb" (and not "absorbs") because the subject is plural: "the earth" AND "the atmosphere" makes two things, plural, so no –S for the third person.
A STRING OF YEARS= Several years in a row.
MEANWHILE= At the same time.
ICE CORES= Scientists drill the ice in the poles and then study the gas trapped inside it, so they can study what was the atmosphere like centuries or thousands of years ago. Those ice bars samples are the "ice cores" they talk about here.
SHRINKING= Becoming smaller.
AS LONG AS= If
RESEARCHERS= People studying scientific data to come to a conclusion.
FAHRENHEIT= A scale to measure temperature designed in Germany and used in all English-speaking countries until recently. Today, it is only used in the USA and some small countries like Belize, the rest of the world uses Celsius degrees, but it is often used by scientists because it’s more precise. An increase of 1 degree Fahrenheit is close to 2 more degrees Celsius.
SUBTLE= Small, not easy to notice.
FORECAST= Predict, announce, say what’s going to happen in the future. The weather forecast is the daily prediction of the coming weather conditions you see on TV.
SEVERE= Grave, serious.
DROUGHT= A long period of time without rain. Pronounced /draʊt/ .
CUTTING GAS EMISSIONS= Reducing or stopping.
SWITCH TO= If you switch to something different, you change what you were doing for that new thing.
LIGHT BULB= A glass sphere that produces light when you let electricity flow into it. Most of the lights we have at home are either fluorescent lights or light bulbs.
COOLER= Less warm, colder.