Christopher Joyce

First of a five-part series

The history of fire in the American Southwest is buried in a catacomb of rooms under the bleachers of the football stadium at the University of Arizona.

Here rules professor Thomas Swetnam, tree ring expert. You want to read a tree ring? You go to Tom. He's a big, burly guy with a beard and a true love for trees.

Second of a two-part series. Read Part 1.

Modern architecture's love affair with tall glass buildings takes a toll. Every year, millions of birds crash into glass windows in North America.

These collisions may seem like an intractable problem. But in New York City, an architect is trying to find a solution.

First of a two-part series. Read Part 2.

Modern architecture loves glass. Glass makes interiors brighter and adds sparkle to cityscapes. But glass also kills millions of birds every year when they collide with windows. Biologists say as more glass buildings go up, more birds are dying.

The last couple of years have certainly felt unusually hot in many parts of the U.S., but are they really all that unusual?

Many people wonder whether a warming climate is turning up the temperature or whether it's all just part of the normal variation in the weather. Among scientists, there's a growing view that these latest heat waves are indeed a result of climate change.

Some of the most interesting discoveries in archaeology come from sifting through ancient garbage dumps. Scientists working in Oregon have found one that has yielded what they say are the oldest human remains in the Americas and a puzzle about the earliest American tools.

Early Americans used Oregon's Paisley Caves for, among other things, a toilet. Little did they know that scientists would be picking through what they left behind.

Geologists have noticed an increase in the number of small earthquakes in the U.S. They suspect the cause to be wastewater wells, where polluted water from industrial processes is pumped deep underground. None of the quakes has caused serious damage.

The famous paintings on the walls of caves in Europe mark the beginning of figurative art and a great leap forward for human culture.

But now a novel method of determining the age of some of those cave paintings questions their provenance. Not that they're fakes — only that it might not have been modern humans who made them.

The first European cave paintings are thought to have been made over 30,000 years ago. Most depict animals and hunters. Some of the eeriest are stencils of human hands, apparently made by blowing a spray of pigment over a hand held up to a wall.

The federal government promised almost 30 years ago to find a place to bury nuclear waste from power plants. It hasn't. So the waste is piling up at power plants around the country.

Now a federal court says the government must prove that this temporary solution is truly safe. The decision could help break the nuclear-waste logjam.

A bizarre event has drawn scientists to a beach in Oregon — a floating concrete dock from Japan has washed ashore. It had been ripped from its moorings by last year's tsunami and floated across the Pacific.

The dock is encrusted with mussels, barnacles and other marine life from Asia. Scientists are amazed these organisms survived the 14-month voyage, but they're also worried some of these organisms could become pests in U.S. waters.

In Pennsylvania, there's an industrial revolution going on. Battalions of drilling rigs are boring into the earth to extract natural gas from an underground layer of shale called the Marcellus formation.

And as the wells multiply all along the western end of the state, people worry they may be facing another toxic legacy.

The first one came from coal mining. All over the state, you can see bright orange rivers and streams. The aquatic life was killed by acidic runoff from abandoned mines.

Archaeologists working in one of the most impenetrable rain forests in Guatemala have stumbled on a remarkable discovery: a room full of wall paintings and numerical calculations.

The buried room apparently was a workshop used by scribes or astronomers working for a Mayan king. The paintings depict the king and members of his court. The numbers mark important periods in the Mayan calendar.

Endurance athletes sometimes say they're "addicted" to exercise. In fact, scientists have shown that rhythmic, continuous exercise — aerobic exercise — can in fact produce narcoticlike chemicals in the body.

Now researchers suggest that those chemicals may have helped turn humans, as well as other animals, into long-distance runners.

The man behind the research is University of Arizona anthropologist David Raichlen, a runner himself. He does about 25 miles a week.

Fossil-hunting scientists are coming to grips with a new discovery that could change forever how we think of dinosaurs. What they've found is that dinosaurs may well have been tortured by large, flealike bloodsucking insects.

Yes, it appears that the greatest predators that ever roamed Earth suffered just as we mammals did — and as we still do. Fleas were thought to have evolved along with mammals — they like our soft skins and a diet of warm blood.

Scientists who watch for earthquakes have discovered a big increase in the number of small quakes in the middle of the country. It's an area that's usually pretty quiet geologically.

The scientists suspect the quakes are caused by wastewater wells. They plan to discuss their findings later this month at a seismology conference, but they've shared the basics with NPR.

Bill Ellsworth, a seismologist at the U.S. Geological Survey, says new technology over the past decade has given scientists a much better feel for when the Earth shakes.

The U.S. Geological Survey will soon confirm that the oil and gas industry is creating earthquakes, and new data from the Midwest finds that these man-made quakes are happening more often than originally thought.

Earthquakes happen when faults in the Earth slip and slide against each other. There's continuous stress on innumerable faults on our continent, but seismologists like Bill Ellsworth, from the U.S. Geological Survey, started seeing something odd about 12 years ago.

Thirty feet long and weighing in at around 3,000 pounds, Yutyrannus huali goes by the nickname "beautiful feathered tyrant." Yutyrannus earned the name "tyrant" because it casually ripped its prey to pieces. But it was also a snappy dresser: The huge predator was covered in downy feathers.

The last big ice age ended about 11,000 years ago, and not a moment too soon — it made a lot more of the world livable, at least for humans.

But exactly what caused the big thaw isn't clear, and new research suggests that a wobble in the Earth kicked off a complicated process that changed the whole planet.

Ice tells the history of the Earth's climate: Air bubbles in ice reveal what the atmosphere was like and what the temperature was. And scientists can read this ice, even if it's been buried for thousands of years.

The Atlantic Ocean, especially the North Atlantic, is peculiar: Every few decades, the average temperature of surface water there changes dramatically.

Scientists want to know why that is, especially because these temperature shifts affect the weather. New research suggests that human activity is part of the cause.

Scientists originally thought that maybe some mysterious pattern in deep-ocean currents, such as an invisible hand stirring a giant bathtub, created this temperature see-saw.

The National Academy of Engineering in Washington, D.C., once asked its members to pick the greatest engineering achievement ever.

Their choice? The electrification of the country through what's known as "the grid."

Ernest Moniz, director of the Energy Institute at MIT, says they were right on the money.

"That reflects what an amazing machine this is, spread out geographically, always having to balance demand and supply because electricity is not stored," he says.

The tsunami that struck Japan last year destroyed four nuclear reactors at the Fukushima Dai-ichi nuclear power station on the east coast of the country. Radiation spread through the air and into the ocean, and workers labored for weeks to quench the melting reactor cores. Farmland and numerous towns were evacuated and much remains off-limits.

Since then, Japan has been temporarily shutting down its remaining nuclear plants as the public debates whether to swear off nuclear power permanently. But saying no to nuclear has been and will continue to be costly.

Peter Gleick is not just any scientist. He got his doctorate at the University of California, Berkeley and won a MacArthur "genius" award. He is also an outspoken proponent of scientific evidence that humans are responsible for climate change.

And earlier this week, he confessed that he had lied to obtain internal documents from the Heartland Institute, a group that questions to what extent climate change is caused by humans.

Rhythm in music is about timing — when notes start and stop. And now scientists say they've found a curious pattern that's common to musical rhythm. It's a pattern also found in nature.

The nuclear industry is celebrating the federal Nuclear Regulatory Commission's decision to give the go-ahead for a utility company to build two new nuclear reactors in Georgia, the first license to be granted for a new reactor in the U.S. since 1978. But last year's accident at reactors in Fukushima, Japan, still clouds the future of nuclear power, as does the cost of new power plants.

Southern Co. will build the reactors at its Vogtle site in Georgia, where two older reactors already operate.

Scientists are reporting that aliens are wiping out the animals in Florida's Everglades.

The aliens are Burmese pythons from Asia. They've been slithering around south Florida for decades. But scientists now say the constrictors are so bad, they're eating their way through the swamps. And the federal government has decided to take action to prevent their spread.

A panel of experts today set forth a plan for getting rid of thousands of tons of highly radioactive nuclear waste.

Most of it is spent fuel from nuclear power reactors. It was supposed to go to a repository in Nevada called Yucca Mountain, but the government has abandoned that plan.

The practice of hydraulic fracturing — pumping fluid into underground rock to push up natural gas — has its detractors, especially among environmentalists. But it's becoming clear that whatever its drawbacks, "fracking," as it's called, is producing a lot of gas — maybe too much gas.

Fracking was once a small part of the natural gas industry, a technique to get hard-to-reach deposits in underground shale. Then the technology improved, and the dinner bell rang. Everybody wanted in. Now there's so much gas on the market that the price is at a 10-year low.

There's a solar trade war going on inside the U.S., sparked by an invasion of inexpensive imports from China.

The U.S. solar industry is divided over these imports: Panel-makers say their business is suffering and want a tariff slapped on the imports. But other parts of the industry say these cheap panels are driving a solar boom in the U.S.

Politically, climate change is off this year's campaign agenda. Jobs, the economy and social issues are front and center.

But scientists are working as hard as ever to figure out how much the Earth is warming and what to do about it. Some now say it's time for a new strategy, one that gets faster results.

Talk to Durwood Zaelke, for example. Zaelke is a grizzled veteran of the climate wars: He was in Kyoto in 1997 when the world's nations drafted a treaty promising to curb warming, and he has watched that promise fizzle while the planet's temperature continues to rise.

Small earthquakes in Ohio and Arkansas associated with hydraulic fracturing for gas have taken many people by surprise. Gas industry executives say there's no hard evidence that their activities are causing these quakes. But some scientists say it's certainly possible; in fact, people have been causing quakes for years.

In the 1960s, geologists realized that gold mines in South Africa had created small earthquakes. Caverns dug into the earth thousands of feet below the surface collapsed. The "pancake" effect caused quakes, in one case a magnitude 5.2 temblor.