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Climate change boosted human development: study
by Staff Writers
Paris (AFP) May 21, 2013


Moore tornado a rarity: experts
Paris (AFP) May 21, 2013 - Tornados, among the most violent of atmospheric storms, rarely reach the size and brutality of the twister that swept through an Oklahoma City suburb on Monday, experts say.

And seldom do they hit built-up areas.

"Typically, they could be about 100 metres (110 yards) across, and they last maybe five to ten minutes on the ground," according to University of Reading meteorologist Ross Reynolds -- who said the people of Moore were in many ways unlucky.

They were confronted by a two-mile- (three-kilometre) wide storm that lasted about 45 minutes and was of a similar strength to the worst-ever tornado that hit the area 14 years ago but claimed fewer lives.

"It is bad luck that a tornado goes in a populated area, normally it is agriculture land... crops or farm buildings," said Reynolds.

"It is a horrible thing when they go through the cities -- the chances of that happening are very small" -- especially in such a sparsely populated region.

Revising a previous higher toll, officials said Tuesday that at least 24 people, including nine children, had died in the Oklahoma storm that packed winds of 166 to 200 miles per hour (267-322 kilometres per hour).

Tornados are spinning columns of air that touch the ground from massive cumulonimbus thunderstorm clouds.

They occur in regions of most continents except for the very coldest areas, and are also common in Argentina and Bangladesh.

The UK is said to get more tornadoes per square kilometre than the United States, but the central and southern American states of Texas, Oklahoma and Kansas get the most violent ones due to unique geographical and meteorological conditions.

Dubbed "Tornado Alley", this is where winds of widely varying temperatures -- warm and moist from the Gulf of Mexico, hot and dry from the desert and cool and dry from the Rocky Mountains and northern plains -- meet in volatile, potent storm clouds called "supercells" that can explode as tornadoes within half an hour from birth.

Most storms occur from May to June, and mainly between 4 pm and 9 pm, according to the US National Oceanic and Atmospheric Administration.

Tornado Alley can see three or four tornados per day in the high season, or about 1,200 for the entire country per year, but only about two percent reach dangerous levels with winds exceeding 265 kph and most of these hit land in rural areas.

According to Reynolds, weather conducive to tornado formation can be predicted a day in advance.

Local forecasters can then keep a careful eye on satellite and radar pictures of cloud- and rain-formation -- send out tornado-spotters to find the storms and estimate their speed and destination.

This allows officials to issue a 15-20-minute warning, hopefully enough time to dive into a tornado centre.

Experts say accurate records are too young and tornadoes too small and sporadic to predict whether they are likely to be impacted by climate change.

There was no proof that they were becoming more frequent or severe, said Reynolds.

"Climate models are currently unable to resolve small-scale phenomena such as tornadoes, and no models exist which can use climate model data to predict future tornado activity," said the UK Met Office.

But Andrew Barrett, also from the University of Reading, said warmer, moister conditions should "provide more energy for the types of storms that produce tornadoes in a warmer climate."

Early humans living in South Africa made cultural and industrial leaps in periods of wetter weather, said a study Tuesday that compared the archaeological record of Man's evolution with that of climate change.

Anatomically modern humans, Homo sapiens, first made their appearance in Africa during the Middle Stone Age which lasted from about 280,000 to 30,000 years ago.

Some of the earliest examples of human culture and technology are found in South Africa -- with fossil evidence of innovative spurts whose cause has left scientists puzzled.

The record reveals that a notable period of human advancement occurred about 71,500 years ago, and another between 64,000 and 59,000 years ago.

Examples of such innovation include the use of symbols, linked to the development of complex language, in engravings, the manufacture and use of stone tools and personal adornment with shell jewellery.

"We show for the first time that the timing of... these periods of innovation coincided with abrupt climate change," study co-author Martin Ziegler of the Cardiff University School of Earth and Ocean Sciences told AFP of the study in the journal Nature Communications.

"We found that South Africa experienced wetter conditions during these periods of cultural advance.

"At the same time, large parts of sub-Saharan Africa experienced drier conditions, so that South Africa potentially acted as a refugium for early humans."

Ziegler and a team reconstructed the South African climate over the past 100,000 years using a sediment core drilled out from the country's east coast.

The core shows changes in river discharge and rainfall.

"It offers for the first time the possibility to compare the archaeological record with a record of climate change over the same period and thus helps us to understand the origins of modern humans," Ziegler said by email.

Co-author Chris Stringer of London's Natural History Museum said the findings supported the view that population growth fuelled cultural advancement through increased human interactions.

"Such climate-driven pulses in southern Africa and more widely were probably fundamental to the origin of key elements of modern human behaviour in Africa and to the subsequent dispersal of Homo sapiens from its ancestral homeland," concluded the study.

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