From arctic to tropics, global warming can give you the chills

It was an odd juxtaposition: As news outlets were reporting last winter about astonishingly frigid conditions in Russia, where nearly 40 deaths had been linked to temperatures as low as 24 degrees below zero, they were also reporting an announcement by climate experts that 2005 was the hottest year worldwide in more than a century.

There, in a nutshell, is the difference between weather and climate. Although that distinction is lost on many people, leading to considerable public confusion about whether global warming is a real threat or just a scare tactic by radical environmentalists bent on prying Americans from their SUVs, it is an important one to make. To understand why nearly every climate expert on the planet believes the industrial world's hundred-year binge on fossil fuels has set the stage for wrenching disruptions, you must look beyond the events of a season or a year.

If you do that, the news only gets worse. And if you really wish to scare yourself, a good place to start is a new book by Mark Bowen, a physicist and mountain climber, "Thin Ice: Unlocking the Secrets of Climate in the World's Highest Mountains."

It is part adventure story, bearing passing resemblance to journalist-climber John Krakauer's bestselling account of disaster on Mount Everest, "Into Thin Air." But Bowen's book also provides a thorough and readable introduction to the evolving science of global warming. The researchers he accompanies spend their time drilling into high-altitude glaciers in the tropics, analyzing ancient ice for clues to the mechanisms and patterns of climate change over millennia.

According to climatologists at the Goddard Institute for Space Studies, the global average temperature last year was the highest in the era of recorded data, which reaches back to the 1890s.

The five warmest years on record have occurred within the past eight years, the scientists reported, reflecting an apparent acceleration in the rate at which the planet is growing warmer. Average global temperature has risen 1.44 degrees in the past century, but 1.08 degrees of that increase have occurred in the past 30 years, they reported.

A century, while a significant span of time in human terms, is not really very long. As every schoolchild learns from picture-book depictions of ice sheets and woolly mammoths, the planet's climate has undergone extreme shifts over longer periods. Until relatively recently, scientists had little idea what caused those shifts, or even how big they were.

That's where researchers such as those in Bowen's book enter the picture. For decades, they've been trundling around the world, looking for ice in the unlikeliest of places: the tropics. Using ingenious machinery, they have bored holes thousands of feet deep into mountaintop glaciers and ice fields, some of which have persisted for more than half a million years, extracting core samples that preserve in their chemistry a record of climate and other conditions prevailing when the precipitation originally fell from the sky.

Ice cores from the polar regions have long been analyzed for similar purposes, but they provide an incomplete picture of global climate dynamics, which appear to be strongly affected by the amount of solar energy falling onto the Earth's surface. Most of that energy enters the atmosphere over the equator, which gives the record preserved in tropical ice particular importance.

Not incidentally, that ice is rapidly vanishing. The famous snows of Kilimanjaro? Gone in 15 years, at the current rate of melting. The same thing is occurring in the Himalayas and the Andes. For that matter, it is also happening in North America, where the glaciers of Glacier National Park will have vanished by 2030, and the Cascades and Sierra Nevada will have lost all or most of their "permanent" ice in the same span. Alaska's glaciers are receding so fast you can practically see it happening. Arctic sea ice coverage is declining by 3 percent a decade and recently reached a record low.

Four years ago, the Larsen B ice shelf in Antarctica - a slab the size of Rhode Island - collapsed and disintegrated.

It may have been a bitterly cold winter in Moscow, but the evidence all points to a much hotter future. And that should be enough to send chills down anyone's spine.

• John Krist is a contributor to Writers on the Range, a service of High Country News (hcn.org). He is a senior reporter for the Ventura County Star in California.