WEBVTT

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As the sun's rays reach 
the Earth's surface

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some are absorbed and re-emitted as heat

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greenhouse gases such as water 
vapor and carbon dioxide

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absorb and re-radiate some of this heat

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increased amounts of greenhouse gases 
in the atmosphere mean more

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heat is trapped

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warming the Earth

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human activities

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especially the burning of fossil 
fuels have increased

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concentrations of atmospheric 
carbon dioxide by 40%

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mainly since 1900

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global average surface temperature 
has increased by 0.8 degrees

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Celsius over that time.

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Other changes to the climate 
in recent decades,

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can be seen in the warming of the oceans.

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A rise in sea level

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decreasing snow and ice cover 
in the northern hemisphere

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and a decline in sea ice in the Arctic.

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If emissions continue unchecked 
then further warming of 2.6 to

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4.8°

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Celsius would be expected by 
the end of the century.

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Even at the low end.

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This would have serious implications 
for human societies

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and the natural world.

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For more information about climate 
change from leading science academies,

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please visit

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royalsociety.org/climatechange

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or nas-sites.org/americasclimatechoices