Why does earth's magnetic field occasionally reverse direction.

Earth's Magnetic Field Reversals Illuminated By Lava Flows Study

ScienceDaily (Sep. 26, 2008) — Earth's north magnetic pole is shifting and weakening. Ancient lava flows are guiding a better understanding of what generates and controls the  – and what may drive it to occasionally reverse direction.

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Earth & Climate

• Atmosphere
• Geology
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Reference

• Mid-ocean ridge
• Shield volcano
• Igneous rock
• Basalt rock

The main magnetic field, generated by turbulent currents within the deep mass of molten iron of the Earth's outer core, periodically flips its direction, such that a compass needle would point south rather than north. Such polarity reversals have occurred hundreds of times at irregular intervals throughout the planet's history – most recently about 780,000 years ago – but scientists are still trying to understand how and why.

A new study of ancient volcanic rocks, reported in the Sept. 26 issue of the journal Science, shows that a second magnetic field source may help determine how and whether the main field reverses direction. This second field, which may originate in the shallow core just below the rocky mantle layer of the Earth, becomes important when the main north-south field weakens, as it does prior to reversing, says Brad Singer, a geology professor at the University of Wisconsin-Madison.  more

Pollution Increases 3 Percent

Global Warming Pollution Increases 3 Percent

Chinese Greenhouse Gas Pollution Largely Responsible for Bringing CO2 Emissions to Record High

By SETH BORENSTEIN AP Science Writer
WASHINGTON September 25, 2008 (AP)

The Associated Press 
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Carbon dioxide output rose 3 percent from 2006 to 2007.

(ABCNews Photo Illustration)

The world pumped up its pollution of the chief man-made global warming gas last year, setting a course that could push beyond leading scientists' projected worst-case scenario, international researchers said Thursday.

The new numbers, called "scary" by some, were a surprise because scientists thought an economic downturn would slow energy use. Instead, carbon dioxide output jumped 3 percent from 2006 to 2007.

That's an amount that exceeds the most dire outlook for emissions from burning coal and oil and related activities as projected by a Nobel Prize-winning group of international scientists in 2007.

Meanwhile, forests and oceans, which suck up carbon dioxide, are doing so at lower rates than in the 20th century, scientists said. If those trends continue, it puts the world on track for the highest predicted rises in temperature and sea level.The pollution leader was China, followed by the United States, which past data show is the leader in emissions per person in carbon dioxide output. And while several developed countries slightly cut their CO2 output in 2007, the United States churned out more.  more 

Food and Agriculture: Global Crop Diversity Trust collects seeds from Azerbaijan to Nigeria

Crop diversity is the raw material needed for improving and adapting food crops to harsher climate conditions and constantly evolving pests and diseases. However, it is disappearing from many of the places where it has been placed for safekeeping—the world's genebanks. Compounding the fact that it is not well conserved is the fact that it is not well understood. A lack of readily available and accurate data on key traits can severely hinder plant breeders' efforts to identify material they can use to breed new varieties best suited for the climates most countries will experience in the coming decades. The support provided by the Global Crop Diversity Trust will not only rescue collections which are at risk, but enable breeders and others to screen collections for important characteristics. 

Read more :- Food and Agriculture: Global Crop Diversity Trust collects seeds from Azerbaijan to Nigeria

Dirt Make More Rain

Moderate Quantities Of Dirt Make More Rain

ScienceDaily (Sep. 17, 2008) — Drought or deluge? Scientists working with Meinrat O. Andreae, Director at the Max Planck Institute for Chemistry in Mainz, have now discovered how aerosols affect the when, where and how much of rainfall.

Until now, the answers to these questions have been as varied as they have been inconsistent. Andreae and his co-authors are now tracing a common theme through the sometimes contradictory effects that these tiny particles have on precipitation.

Their new approach: they are observing how aerosols change the flow of energy in the atmosphere and thus air circulation, the way drops form and the way they fall. Because the role of aerosols has to date been very much a subject of dispute and a source of great uncertainty in climate predictions made by researchers, this work removes one of the largest obstacles to the development of more accurate climate forecasts.

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Threat of global warming justifies breaking the law

Jury decides that threat of global warming justifies breaking the law

By Michael McCarthy, Environment Editor
Thursday, 11 September 2008

PA

The Kingsnorth Six leave Maidstone Crown Court after being found not guilty of causing criminal damage during a protest at a coal-fired power station in Kent

The threat of global warming is so great that campaigners were justified in causing more than £35,000 worth of damage to a coal-fired power station, a jury decided yesterday. In a verdict that will have shocked ministers and energy companies the jury at Maidstone Crown Court cleared six Greenpeace activists of criminal damage.

Jurors accepted defence arguments that the six had a "lawful excuse" to damage property at Kingsnorth power station in Kent to prevent even greater damage caused by climate change. The defence of "lawful excuse" under the Criminal Damage Act 1971 allows damage to be caused to property to prevent even greater damage – such as breaking down the door of a burning house to tackle a fire.

The not-guilty verdict, delivered after two days and greeted with cheers in the courtroom, raises the stakes for the most pressing issue on Britain's green agenda and could encourage further direct action.  More

Rajendra Pachauri, chairperson of the IPCC:Shun meat to combat global warming

Shun meat, says UN climate chief

By Richard Black  Environment correspondent, BBC News website Livestock production has a bigger climate impact than transport, the UN believes People should consider eating less meat as a way of combating global warming, says the UN's top climate scientist. Rajendra Pachauri, who chairs the Intergovernmental Panel on Climate Change (IPCC), will make the call at a speech in London on Monday evening. UN figures suggest that meat production puts more greenhouse gases into the atmosphere than transport. But a spokeswoman for the UK's National Farmers' Union (NFU) said methane emissions from farms were declining. "The UN Food and Agriculture Organization (FAO) has estimated that direct emissions from meat production account for about 18% of the world's total greenhouse gas emissions," he told BBC News. "So I want to highlight the fact that among options for mitigating climate change, changing diets is something one should consider. Read more