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There are millions of measurements
over the last hundred and 40 odd years.

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We put those together.

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We're using data
from literally tens of thousands

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of different stations around the world.

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We use the information
that's there to create a global picture

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of what's happening.

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And that gives us a very accurate

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estimate of how any year ranks or what the

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what the anomaly is for
any one year compared to what happened

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in the 19th century or what happened
in the middle of the 20th century.

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So we have our statistical reconstruction
of Earth's recent climate.

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But in research science,
we like to check our work.

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There are a couple of ways
we can do this.

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First of all, teamwork. Our colleagues at NOAA, and at other agencies

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and universities around the world, also create their own records, and

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we can line them up side-by-side, and see just how closely they align. 

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Everyone's independent climate records
show the same thing:

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Earth is warming significantly and rapidly. 

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And here at NASA, we have an even cooler way to check our work:

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space!

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Right now, we have more than

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two dozen satellites dedicated
just to studying our planet.

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Satellites can take measurements of the entire planet,

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and line them up with our estimate of global temperature change. 

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And sure enough,

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they also match!

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Our measurements from space match up well with what our analysis tell us:

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Earth's climate is warming.