* Astronomy

An epic drought during the mid-1100s dwarfs any drought previously documented for a region that includes areas of Arizona, Colorado, New Mexico, Utah and Wyoming.
The six-decade-long drought was remarkable for the absence of very wet years. At the core of the drought was a period of 25 years in which Colorado River flow averaged 15 percent below normal.
The new tree-ring-based reconstruction documents the year-by-year natural variability of streamflows in the upper Colorado River basin back to A. D. 762, said the tree-ring scientists from The University of Arizona in Tucson who led the research team.
The work extends the continuous tree-ring record of upper Colorado streamflows back seven centuries earlier than previous reconstructions.

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Volcanoes blamed for prehistoric global warming
Scientists say eruptions set off a chain reaction, causing a massive release of carbon that super-heated Earth.
Scientists believe they have solved the mystery of what caused the most rapid global warming in known geologic history, a cataclysmic temperature spike 55 million years ago driven by concentrations of greenhouse gases hundreds of times greater than today.
The culprit, the researchers reported Thursday in the journal Science, was a series of volcanic eruptions that set off a chain reaction releasing massive amounts of carbon into the atmosphere.
The eruptions occurred on the rift between two continental plates as Greenland and Europe separated.
In 10,000 years a blip in Earth's history the polar seas turned into tropical baths, deep-sea microorganisms went extinct, and mammals migrated poleward as their habitats warmed.
It took about 200,000 years for the atmospheric carbon to transfer to the deep ocean, allowing the planet to cool.
The event, known as the Palaeocene-Eocene Thermal Maximum, was discovered in the early 1990s. Since then, scientists have studied it to better predict how Earth will respond to the current buildup of greenhouse gases.

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Scientists at Queens University Belfast have uncovered evidence that stoats survived in Ireland at the coldest point of the last Ice Age, 23,500 years ago.
The research has revealed that despite few animals or plants surviving the millennia of freezing cold and ice, the Irish stoats had real staying power. The Irish lineage of these small carnivores that eat mice, rabbits and birds is unique according to the research.
The scientists reached their conclusions by studying the wiry mammals DNA collected from museum collections and gamekeepers.

These tenacious carnivores probably survived the extreme cold at the peak of the last Ice Age by living under the snow and eating lemmings, just as they do in Greenland today - Dr Robbie McDonald, Manager of Quercus at Queens.

Source Queens University Belfast

ABRUPT CLIMATE CHANGE FAR MORE COMMON THAN PREVIOUSLY THOUGHT

MADISON - It came on quickly and then lasted nearly two decades,  eventually killing more than one million people and affecting 50 million  more. All of this makes the Sahel drought, which first struck West Africa  in the late 1960s, the most notorious example of an abrupt climatic  shift during the last century.
Dramatic as this single event was, University of Wisconsin-Madison  researchers have now uncovered 29 other regions worldwide that endured  similarly precipitous climatic changes during the 20th century - far more  than scientists previously thought. Their study publishes today (March  30) in the online edition of Geophysical Research Letters.
The work represents the first systematic survey of abrupt climate  changes that have occurred in recent history, says postdoctoral researcher  Gemma Narisma, who led the study with professor Jonathan Foley, director  of the UW-Madison Centre for Sustainability and the Global Environment  in the Nelson Institute for Environmental Studies. The National  Academies' National Research Council has called for more research on abrupt  climate change, warning that it's more likely to happen as global  temperatures rise and humans continue to alter the environment.

"This study is important, because previous work largely focused on  ancient climates or theoretical changes in future climates. But our work here is showing that abrupt climatic changes are real, are  with us today, and that they have major impacts on human societies" - Jonathan Foley.

By identifying diverse regions around the globe where rapid climatic  shifts have taken place, the study opens up new opportunities for  understanding why these changes happen and what makes areas susceptible to  them. A range of factors is likely involved, including human  activities, such as deforestation and land degradation, and natural  phenomena, like sea surface temperatures.
The work might also lead to interventions that would make systems less  vulnerable to sudden climate change.
Unlike other research studies, which have focused on sudden shifts in  ancient climates or possible future changes, Narisma's survey of abrupt  climate change during the past 100 years offers something else: a  chance to learn how people coped.

"We're interested in the human side mainly. In the more  recent history, you really get to see what the impacts were on the  current society, and that gives you an idea of the potential impacts in the  future, as well"  - Gemma Narisma.

Abrupt climate change is generally known as a quick and drastic shift  in climate that makes it difficult for society and the environment to  adapt. In the study, Narisma and her colleagues defined it as a drop in  rainfall to levels at least five percent below the normal average, which  took much less time to settle in than the drought's total length. They  also stipulated that drought conditions had to last at least five  years.

"Since these changes are a switch to a new state - the drought state -  the tendency is for them to persist for awhile. It's  the combination of abruptness and persistence that gives these events the  potential to have serious consequences" - Gemma Narisma.

The scientists pored over precipitation records from 1901 to 2000 and  then used wavelet analysis and statistical techniques to pinpoint  climate shifts matching their criteria. In addition to familiar events, such  as the Sahel drought and the Dust Bowl in the Midwestern United States,  they detected lesser-known droughts in virtually all corners of the  globe, including Europe, North America, Australia, China, the former  Soviet Union, the Middle East, Africa, India and Bangladesh.
 Although diverse geographically, the 30 affected regions were mostly  arid or semi-arid, says Narisma, a result consistent with other modelling  studies. Most saw rainfall decrease by 10 percent or more below normal  levels, and in all cases drought lasted for at least 10 years.
Why is abrupt climate change of such concern today? Narisma thinks much  of it traces back to the tragedy in the Sahel, whose causes - and  terrible consequences - have been well documented.

"The Sahel and the Dust Bowl had huge impacts. But we  thought that before we can even begin to analyse the mechanisms behind these  abrupt changes or their potential impacts, we had to ask ourselves,  'Are there other regions where abrupt changes have occurred?' We think  this study is a major first step in answering these questions" - Gemma Narisma.

The paper's other authors are Rachel Licker of the Nelson Institute and  Navin Ramankutty of McGill University in Montreal, Canada

UW-Madison News Release