The most populated state in the country is facing what may be its worst drought in a century of record-keeping. On January 20, the governor of California declared a state of emergency, urging everyone to begin conserving water.

Concentration of carbon dioxide is about 1.4 times what it was before the Industrial Revolution. How much and how fast will Earth warm if carbon dioxide concentrations double the pre-industrial?

The Arctic Oscillation describes simultaneous, geographically “choreographed” shifts in multiple features of the polar vortex: air pressure, temperature, and the location and strength of the jet stream. They all follow the hemisphere-wide oscillation of atmospheric mass back and forth between the Arctic and the middle latitudes, sort of like water sloshing in a bowl.

A few days of unusually cold weather in the U.S. and Canada aren't a sign that a century-or-more trend of rising global surface temperatures has reversed itself. In fact, the cold wasn't even all that widespread for the Northern Hemisphere.

From reindeer to regional temperature patterns, from sea ice age to Greenland surface melt, the Arctic Report Card is a yearly assessment of the Arctic's physical and biological systems and how they are changing. This collection of visual highlights from the 2013 report is a story of the Arctic in pictures.

Since the mid-1960s, the Arctic has warmed about 3.6°F (2.0°C)—more than double the amount of warming in lower latitudes. In 2012 (the last complete calendar year available at the time scientists began working on the 2013 Arctic Report Card), the annual average temperature was the sixth warmest on record.

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