[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.

[01:32.41]