Lauren Sommer

Next week, President Biden will announce a number that could shape the rest of his presidency: a new goal to cut U.S. greenhouse gas emissions.

They're purple, spiky and voracious, and just off the West Coast, there are more of them than you can count.

Purple sea urchins have exploded in recent years off California, covering the ocean floor in what divers describe as a "purple carpet." And they devour kelp: the once-lush forests of seaweed that hugged the coastline are disappearing. Since 2014, 95 percent of the kelp have vanished across a large part of Northern California, most of it bull kelp.

A few years ago, marine biologist Kyle Van Houtan spotted an online video that he couldn't quite believe. It showed a young great white shark, about five-feet long, swimming just off a pier in Central California.

"Our initial reaction was that it can't be true," Van Houtan says. "We know that they're in Southern California and Mexico, not in Monterey."

When they're young, white sharks typically live in the warm waters of Southern California, hundreds of miles from the cold, rough surf up north off Monterey.

As the blackouts in Texas dragged on, millions of residents quickly realized they had more to worry about than trying to light and heat their homes. The water coming out their faucets was no longer safe to drink.

Like falling dominos, infrastructure around Texas, dependent on electricity, began failing in the extreme cold. In Austin, the Ullrich Water Treatment Plant shut down due to an electrical failure. That, combined with low water pressure from broken pipes, meant residents had to boil their water.

Off the coast of England, there's a tiny, wind-swept island with the remains of a lifeboat rescue station from the mid-1800s. The workers who once ran the station on Hilbre Island did something that, unbeknownst to them, has become crucial for understanding the future of a hotter climate: They recorded the tides.

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