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Global Warming 101 | National Geographic

00:00:00for 2.5 million years the Earth’s

00:00:03climate has fluctuated cycling from ice

00:00:06ages to warmer periods but in the last

00:00:09century the planets temperature has

00:00:11risen unusually fast about 1.2 to 1.4

00:00:15degrees Fahrenheit scientists believe

00:00:19it’s human activity that’s driving the

00:00:21temperatures up a process known as

00:00:23global warming

00:00:25ever since the industrial revolution

00:00:27began factories power plants and

00:00:30eventually cars have burned fossil fuels

00:00:33such as oil and pole releasing huge

00:00:36amounts of carbon dioxide and other

00:00:38gases into the atmosphere these

00:00:41greenhouse gases trap heat near the

00:00:44earth through a naturally occurring

00:00:45process called the greenhouse effect the

00:00:47greenhouse effect begins with the Sun

00:00:50and the energy it radiates to the earth

00:00:52the earth and the atmosphere absorbs

00:00:55some of this energy while the rest is

00:00:57radiated back into space

00:01:00naturally-occurring gases in the

00:01:02atmosphere trap some of this energy and

00:01:04reflected back warming the earth

00:01:07scientists now believe that the

00:01:09greenhouse effect is being intensified

00:01:10by the extra greenhouse gases that

00:01:13humans have released evidence for global

00:01:16warming includes a recent string of very

00:01:18warm years scientists report that 1998

00:01:22was the warmest year in measured history

00:01:24with 2005 coming in second meanwhile

00:01:28readings taken from ice cores show that

00:01:30the greenhouse gases carbon dioxide and

00:01:33methane have hit their highest levels in

00:01:35the past 420 thousand years

00:01:39Arctic sea ice is also shrinking

00:01:42according to NASA studies the extent of

00:01:45Arctic sea ice has declined about 10

00:01:47percent in the last thirty years as long

00:01:50as industrialized nations consume energy

00:01:53and developing countries increase their

00:01:55fossil fuel consumption the

00:01:57concentration of greenhouse gases in the

00:01:59atmosphere will continue to rise

00:02:02researchers predict that temperatures

00:02:04will increase about two to ten degrees

00:02:06Fahrenheit by the end of the century

00:02:08what’s less certain is what rising

00:02:11temperatures mean for the planet some

00:02:13climate models predict subtle changes

00:02:16others forecast rising sea levels which

00:02:19could flood coastal areas around the

00:02:21world weather patterns could change

00:02:24making hurricanes more frequent severe

00:02:27droughts could become more common in

00:02:29warm areas and species unable to adapt

00:02:32to the changing conditions would face

00:02:34extinction although much remains to be

00:02:38learned about global warming

00:02:39many organizations advocate cutting

00:02:42greenhouse gas emissions to reduce the

00:02:44impact of global warming

00:02:46consumers can help by saving energy

00:02:49around the house switching to compact

00:02:51fluorescent light bulbs and driving

00:02:54fewer miles in the car each week these

00:02:57simple changes may help keep the earth

00:02:59cooler in the future