Richard Harris

Arctic sea ice has melted dramatically this summer, smashing the previous record. The Arctic has warmed dramatically compared with the rest of the planet, and scientists say that's what's driving this loss of ice.

To be sure, ice on the Arctic Ocean always melts in the summer. Historically, about half of it is gone by mid-September. But this year, three-fourths of the ice has melted away, setting a dramatic new benchmark.

Mitt Romney outlined an energy plan Thursday that would guide his Republican presidency. It focuses heavily on expanding the supply of fossil fuels. The presumptive nominee said the U.S., Mexico and Canada together could reach energy independence by 2020.

But the plan makes no mention of climate change and would end subsidies for cleaner sources of energy, such as wind and solar.

Ten years ago, a piece of ice the size of Rhode Island disintegrated and melted in the waters off Antarctica. Two other massive ice shelves along the Antarctic Peninsula had suffered similar fates a few years before. The events became poster children for the effects of global warming. But a new study finds that the story isn't quite so simple.

There's no question that unusually warm air triggered the final demise of these huge chunks of ice. But a lingering question is whether these events can be attributed to human-induced global warming.

It may take some time to pinpoint the exact cause of India's massive blackouts last week, but the underlying issue for India and many other parts of the developing world is that supply is struggling to keep up with the growing demand for power — an imbalance that can affect the reliability of electric grids.

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STEVE INSKEEP, HOST:

This next story takes on some new scientific research involving wily rodents, rodents that run around through the rainforest stealing mercilessly from one another. That doesn't sound very nice, but they're actually providing a service for the forest that may once have been provided by wooly mammoths.

NPR's Richard Harris could not resist telling a story with such an intriguing cast of characters.

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RENEE MONTAGNE, HOST:

You might think that Americans, renowned for consuming a disproportionate share of the Earth's resources, would feel the most guilty about using up those resources. Not so, according to a new study. NPR's Richard Harris reports on the latest findings from a National Geographic project called Greendex.

How much of the recent hot weather can be attributed to global warming? Scientists will no doubt dig into the data and grapple with that question in the months to come. They have already taken a stab at that question regarding some of last year's extreme weather events, like the drought in Texas.

Before we get to the fireworks on the Fourth of July, we might see some pyrotechnics from a giant physics experiment near Geneva, Switzerland.

Scientists there are planning to gather that morning to hear the latest about the decades-long search for a subatomic particle that could help explain why objects in our universe actually weigh anything.

The buzz is that they're closing in on the elusive Higgs particle. That would be a major milestone in the quest to understand the most basic nature of the universe.

The Rio+20 Conference on Sustainable Development was the biggest United Nations conference ever, but it may be one of the biggest duds. It produced no major agreements — just a vaguely worded declaration that has been widely derided.

More than 45,000 people registered for the event in Rio de Janeiro, but diplomats couldn't even agree about the meeting's objective until 2:45 a.m. on Tuesday, just before heads of state and other high-level delegates started arriving in Rio.