[00:04.53]Unit 22 Environmental Protection
[00:08.85]Lesson 1 Global Warming
[00:12.39]Can we take the heat?In the last few decades,
[00:16.95]environmentalists have reported
[00:19.02]that human beings are causing changes
[00:22.29]in the Earth's climate-something previously
[00:25.41]seen as beyond our control.
[00:28.56]They claim that since the Industrial Revolution
[00:31.55](1750)and especially in the last 50 years,
[00:35.25]gases pumped into the Earth's atmosphere
[00:38.08]by our factories and vehicles
[00:40.47]have been speeding up the process of global
[00:43.16]warming and there by affecting our climate.
[00:47.40]Scientists believe that global warming
[00:49.93]could be one of the biggest environmental
[00:52.46]problems facing the 21st century,
[00:55.62]but what exactly is global warming
[00:58.57]and why is it seen as a threat?
[01:02.02]Global warming refers to an average increase
[01:06.07]in the Earth's temperature that,
[01:08.32]in turn,leads to climate change.
[01:11.93]Scientists found that the temperature
[01:14.31]of the Earth is controlled
[01:15.67]by greenhouse gases such as carbon dioxide,
[01:19.46]that trap heat from the sun
[01:21.87]in the Earth's atmosphere.
[01:23.77]Without these naturally occurring gases,
[01:26.79]the sun's energy would be radiated
[01:29.61]back into space leaving the earth could
[01:32.41]and unsuitable for life.
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