Christopher Joyce

On Florida's Gulf coast Tuesday, there will be a celebrated homecoming. For a turtle. This is no ordinary turtle: Known as Johnny Vasco da Gama, after the 15th-century Portuguese explorer, it crossed the Atlantic twice — by sea and by air.

Johnny, as his human friends call him, is a critically endangered Kemp's ridley turtle. Only a few thousand of these sea-turtles exist, mostly in the Gulf of Mexico. Normally, they do not migrate across the Atlantic.

Some climate strategists are looking beyond the United Nations and the idea of remaking the energy economy — and toward the world's tropical forests.

The basic idea is to provide rich countries that emit lots of climate-warming gases another way to reduce their carbon footprint besides replacing or retrofitting factories and power plants. Instead, they could just pay poorer countries to keep their forests, or even expand them. Forests suck carbon out of the atmosphere. It's like paying someone to put carbon in a storehouse.

In archaeology, you get special bragging rights when you can lay claim to the oldest specimen of something.

Scientists in South Africa may now qualify for what they say is the world's oldest bed. Well, not a bed exactly, but more like a mattress made of grass.

What Lyn Wadley, an archaeologist at the University of Witswatersrand, found were mats of grass and sedge piled half an inch thick on the floor of a cavelike rock shelter in South Africa.

Second of a two-part series on California's climate policies. Read part 1.

Climate experts are exploring the concept of growing dense fields of weeds to help soak up carbon dioxide from the atmosphere.

Just over a year from now, California will begin enforcing a set of laws that limit emissions of greenhouse gases from factories, power plants and, eventually, from vehicles.

First of a two-part series on California's climate policies

California is about to try a radical experiment. A little over a year from now, the state will limit the greenhouse gas emissions from factories and power plants, and, eventually, emissions from vehicles.

The U.S. Congress tried to pass a similar plan for the whole country but dropped the idea last year.

In 1977, a small crew of oceanographers traveled to the bottom of the Pacific Ocean and stumbled across a brand new form of life. The discovery was so unusual, it turned biology on its head and brought into question much of what scientists thought they knew about where life can form and what it needs in order to survive.

A scientist in Boston has been driving around the city measuring leaks in the gas mains. He's found a lot, and he wants the public to know where they are.

Gas leaks aren't uncommon, and gas companies spend a lot of time tracking them down and repairing them. But the scientific team says they're surprised at how many they've found, and what those leaks are doing to the health of the city's trees.

Apparently one of the earliest human instincts was to paint things, including bodies and cave walls. That's the conclusion from scientists who have discovered something remarkable in a South African cave — a tool kit for making paint. It looks to be the oldest evidence of paint-making.

Over in southern Africa 100,000 years ago, Homo sapiens was pretty new on the scene. A favorite hangout was a cave named Blombos near the Southern ocean.

It's dawn and 40 degrees out. The air tastes of dust. Elias Neftali is behind the wheel of a truck, driving us through a long valley encircled by red-rock mountains. As a farmhand in the northwest desert of Namibia, Neftali used to shoot wild animals trying to eat his livestock.

Now he protects wild animals. And that can be scary.

"Oh my god, yep," he says. He tells me about a night he was sleeping in a bungalow out in the bush with some other wildlife guards.

The notion of "beauty" can mean many different things to artists. For the Brothers Quay — identical-twin filmmakers — it often means dimly lit black and white images of animated dolls, screws, cogs — any manner of inanimate object brought to life. They're so good at it that fellow filmmaker Terry Gilliam called the Quays' Street of Crocodiles one of the best animated films of all time.

The back rooms of museums are like your grandparents' attic, only the stuff is more exotic — things like fossilized jellyfish, dinosaur eggs, or mummified princes.

And if you look carefully, you'll find objects that once changed science but are now largely forgotten. You might call them Lost Treasures of Science. This is a story of one of those objects — a special bone that's part of a special skeleton.

A pair of fossils from a South African cave have scientists both excited and puzzled. Scientists say the fossils — an adult female and a juvenile — could be the long-sought transition between ape-like ancestors and the first humans.

The bones belong to creatures related to the famous Lucy fossil found in Ethiopia in the 1970s, but their owners lived more recently, just two million years ago.

The Tibetan Plateau is the world's highest place. It's four times the size of France and home to most of the world's highest mountains.

As you might expect, it's cold there. And it may be that the deep chill of the Tibetan Plateau played a role in the evolution of some of the world's most charismatic animals.

That's the belief of a scientist who discovered the skull of a woolly rhino on the Tibetan Plateau.

Drive through northern Pennsylvania and you'll see barns, cows, silos and drilling rigs perched on big, concrete pads.

Pennsylvania is at the center of a natural gas boom. New technology is pushing gas out of huge shale deposits underground. That's created jobs and wealth, but it may be damaging drinking water. That's because when you "frack," as hydraulic fracturing is called, you pump millions of gallons of fluids underground. That cracks the shale a mile deep and drives natural gas up to the surface — gas that otherwise could never be tapped.