Global warming is one symptom of the much larger problem of human-caused climate change.

On the afternoon of May 23, Alaska set a new statewide record for the earliest day in the year with a temperature in the 90s.

Montzka in a snow pit in Antarctica

Some of the chemicals that replaced ozone-harming CFCs are long-lived greenhouse gases. At NOAA's lab in Boulder, Colorado, chemist Steve Montzka leads the effort to monitor the concentration of CFC-substitutes and their potential impact on global warming.

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