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The evidence
The latest science has shown that global concentrations of greenhouse gases in the Earth's atmosphere have increased markedly as a result of human activities since 1750. The levels now far exceed pre-industrial values, shown by analysis of ice cores spanning many thousands of years.
The great majority of scientists agree that increases in greenhouse gas emissions have caused overall temperatures to rise gradually over this period, by trapping more of the sun's heat.
Widespread changes in extreme temperatures have been observed over the last 50 years. Cold days, cold nights and frost have become less frequent, while hot days, hot nights, and heat waves have become more frequent.
Eleven of the last twelve years (1995 -2006) rank among the 12 warmest years since 1850.
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