Climate scientists discuss what they know about global climate change today, and how they know it.

The Southern Oscillation Index tracks differences in air pressure between the eastern and western sides of the tropical Pacific.

Temperatures measured on land and at sea for more than a century show that Earth's globally averaged surface temperature is experiencing a long-term warming trend.

The 2015-2016 El Niño will go down as one of the strongest on record, and also, thanks to El Niño Rapid Response Campaign, one of the best observed.

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