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
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