paleoclimatology

Human civilization arose during the relatively balmy climate of the last 10,000 years. Even so, evidence is accumulating that at least two cold spells gripped the northern hemisphere during this time, and that the cooling may have coincided with drought in the tropics. Emerging research on climate during this Holocene period suggests that temperature swings were more common than previously thought, and that climate changes happened on a broad, hemispheric scale.

The seas are rising, as they have during past periods of warming in earth’s history. Estimates of how high they will go in the next few thousand years range from five meters, putting greater Miami underwater, to 40 meters, wiping most of Florida off the map. “The range of estimates is huge to the point of meaninglessness,” says

Maureen “Mo” Raymo

, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory.

We may think of the Pacific Northwest as rain-drenched, but new research led by scientists at the University of Pittsburgh shows that the region could be in for longer dry seasons, and is unlikely to see a period as wet as the 20th century any time soon.

Scientists have long known that large volcanic explosions can affect the weather by spewing particles that block solar energy and cool the air. Some suspect that extended “volcanic winters” from gigantic blowups helped kill off dinosaurs and Neanderthals...

Scientists still puzzle over how Earth emerged from its last ice age, an event that ushered in a warmer climate and the birth of human civilization. In the geological blink of an eye, ice sheets in the northern hemisphere began to collapse and warming spread quickly to the south. Most scientists say that the trigger...

New results from a drilling expedition off Antarctica may help scientists learn more about a dramatic turn in climate 34 million years ago, when the planet cooled from a “greenhouse” to an “icehouse” state. In just 400,000 years – a blink of an eye in geologic time – carbon dioxide levels dropped, temperatures plunged and ice sheets formed over what was then the lush continent of Antarctica.

Decades of drought, interspersed with intense monsoon rains, may have helped bring about the fall of Cambodia’s ancient Khmer civilization at Angkor nearly 600 years ago, according to an analysis of tree rings, archeological remains and other evidence.

Scientists aboard the research ship the JOIDES Resolution recently drilled two kilometers into Earth’s crust, setting a new record for the deepest hole drilled through the seafloor on a single expedition.

Researchers have reconstructed atmospheric carbon dioxide levels over the past 2.1 million years in the sharpest detail yet, shedding new light on its role in the earth’s cycles of cooling and warming.

But Global Warming May Have Helped Override Some Recent Eruptions

Climate researchers have shown that big volcanic eruptions over the past 450 years have temporarily cooled weather in the tropics—but suggest that such effects may have been masked in the 20^th century by rising global temperatures

 A study released on May 11, 2007 provides some of the first solid evidence that warming-induced changes in ocean circulation at the end of the last Ice Age caused vast quantities of ancient carbon dioxide to belch from the deep sea into the atmosphere. Scientists believe the carbon dioxide (CO2) releases helped propel the world into further warming.

The end of the recurring, 100,000-year glacial cycles is one of the most prominent and readily identifiable features in records of the Earth's recent climate history. Yet one of the most puzzling questions in climate science has been why different parts of the world, most notably Greenland, appear to have warmed at different times and at different rates after the end of the last Ice Age.