"It was a large ball of flame," Rural/Metro Fire Department spokeswoman Alison Cooper said. "It was very large. It was seen as far as Washington state." advertisement

Kip and Valerie Wachter saw the fireball pass over their heads about 10:15 Sunday evening as they walked north of Pinetop.

"The colors were a bright green, red, white. The size was about three times wider than its length. It seemed to emanate a low, soft swishing sound as it passed overhead," the Wachters wrote in an e-mail to The Republic.

Steve Kates, a Chandler resident and science journalist known as "Dr. Sky," said that description, particularly the noise, was consistent with meteoric activity.

Most meteors visible on earth occur high in the atmosphere and these "shooting stars" are about the size of a grain of dust, said Jeffrey Hall, associate director at the Lowell Observatory in Flagstaff.

"The great majority are these tiny particles moving through the atmosphere at a high rate of speed," Hall said. "Larger ones tend to be moving more slowly and produce a much larger trail through the sky."

Between 10 and 50 meteor events occur over the Earth each day, according to the American Meteor Society, with the vast majority happening over oceans and out of eyesight. Meteors lose mass and decelerate as they enter the atmosphere, with only the largest slamming into the Earth and forming a crater. Scientists think the Barringer Crater, near Winslow, was formed by an iron meteor about 50,000 years ago.

Kates said a meteorite the size of a human fist could have created the light show West Coast residents witnessed Sunday night.

Rural/Metro responded to the north side of Saguaro Lake but found no sign of damage or destruction from a plane crash, Cooper said. Witnesses reported seeing the meteor travel from southwest to northeast.

Hall said the meteor likely never made it to the ground.

"This is not like a mountain coming into the atmosphere. It's more like the size of a softball," Hall said. "Even something this bright probably burned up completely in the atmosphere."

To investigate, Slott and his colleagues modelled how increasingly powerful waves striking the Carolina Capes over the next 200 years would change the shape of the coastline. They assumed that a 2 °C rise in sea surface temperatures would raise wind speeds by 10 per cent.

Rather than eroding the shore uniformly, the team found that the waves removed sand from the beaches in some regions and re-deposited it elsewhere. Significantly, the sea encroached some areas 10 times further than would be expected from rising water levels alone (Geophysical Research Letters, vol 33, p L18404).

Slott points out that some of the fastest-growing communities in North Carolina are building near the coast. "We want those involved in managing coastlines - and the people living there - to realise that the story is more complicated than they might think," says Slott.

From issue 2571 of New Scientist magazine, 30 September 2006, page 20

"One of the things we're debating in the world right now is whether global warming might increase the storminess in the oceans," MacAyeal said in a statement.

"The question we then pose is: Could global storminess have an influence on the Antarctic ice sheet that had never been thought of?"

The researchers were watching icebergs using satellite images, and saw that on a clear, calm day last October, a big iceberg known as B15A broke into half a dozen pieces.

MacAyeal and colleagues had put seismometers and other instruments on the 60 mile long iceberg and on Antarctica's Ross Ice Shelf.

"We are trying to figure out how the icebergs are sort of making music when various phenomena that we think are linked to the cracking of iceberg masses takes place," Okal said.

So when they saw B15A break up, they persuaded other researchers in Antarctica to fly over to the beg and get their instruments.

The seismometer record showed that although it was mild and clear, the iceberg had been moving up and down and from side to side.

"I was surprised at the level of amplitude that we were recording," Okal said. The researchers figured a storm somewhere may have generated waves, which are known to travel long distances.

They did some calculations and saw the swell must have come from more than 8,000 miles or 13,500 km away.

"Our jaws dropped," MacAyeal said. "We looked in the Pacific Ocean and there, 13,500 kilometers away, six days earlier, was the winter season's first really big, nasty storm that developed and lasted for about a day and a half in the Gulf of Alaska."

They looked at records from wave buoys in between.

"We saw that the waves in Alaska were about 35 feet (10 meters) tall and then two days later they were down to 15 feet

as they passed Hawaii on their way south," MacAyeal said.

And three days later, a sensitive seismometer on Pitcairn Island in the south Pacific recorded the waves' passage.

"We think that B15A was in the right position where these waves would be fatal to it," MacAyeal said. "The iceberg shattered like a gracile wine glass being sung to by a heavy soprano."

This year's record ozone loss was reached because these two measurements occurred during the same time period. (A Dobson unit is a unit of measurement that describes the thickness of the ozone layer in a column directly above the location being measured.)

"Such significant ozone loss requires very low temperatures in the stratosphere combined with sunlight. This year's extreme loss of ozone can be explained by the temperatures above Antarctica reaching the lowest recorded in the area since 1979," ESA Atmospheric Engineer Claus Zehner said.

Ozone is a protective layer found about 25 kilometres above us mostly in the stratospheric stratum of the atmosphere that acts as a sunlight filter shielding life on Earth from harmful ultraviolet rays. Over the last decade the ozone level has lowered by about 0,3% per year on a global scale, increasing the risk of skin cancer, cataracts and harm to marine life.

The thinning of the ozone is caused by the presence of pollutants in the atmosphere such as chlorine, originating from man-made pollutants like chlorofluorocarbons (CFCs), which have still not vanished from the air despite being banned under the Montreal Protocol (1987).

During the southern hemisphere winter, the atmospheric mass above the Antarctic continent is kept cut off from exchanges with mid-latitude air by prevailing winds known as the polar vortex. This leads to very low temperatures, and in the cold and continuous darkness of this season, polar stratospheric clouds are formed that contain chlorine.

As the polar spring arrives, the combination of returning sunlight and the presence of polar stratospheric clouds leads to splitting of chlorine compounds into highly ozone-reactive radicals that break ozone down into individual oxygen molecules. A single molecule of chlorine has the potential to break down thousands of molecules of ozone.

The ozone hole, first recognised in 1985, typically persists until November or December, when the winds surrounding the South Pole (polar vortex) weaken, and ozone-poor air inside the vortex is mixed with ozone-rich air outside it.

Envisat, the largest Earth observation satellite ever built, can localise ozone depletion and track its changes, enabling the rapid estimation of UV radiation as well as providing forecasting. The three atmospheric instruments aboard Envisat are the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY), the global ozone monitoring by occultation of stars (GOMOS) sensor and the Michelson interferometer for passive atmospheric sounding (MIPAS).

In the framework of GMES (Global Monitoring of the Environment and Security), ESA has backed a project named TEMIS (Tropospheric Emission Monitoring Internet Service) that provides operational ozone and UV radiation monitoring based on SCIAMACHY and GOME-1 data. The ozone-monitoring data provided by these instruments span a time period of 11 years, which will be extended by the upcoming MetOp satellite series.

The first MetOp satellite in the series of three is scheduled to be launched in 2006 and will assist climate researchers in monitoring ozone levels and other atmospheric parameters. MetOp - Europe's first polar-orbiting satellite and a mission dedicated to operational meteorology - will include a next-generation ozone-monitoring instrument called GOME-2, intended to guarantee continuity of observation of this vital environmental factor well into the following decades.

"Long-term measurements of ozone levels are of key importance for being able to monitor the ozone's predicted recovery, which is currently estimated to take place by around 2060," Zehner said.

Since the ban on the chemically related CFCs, HFC134a has been manufactured in ever growing quantities for use in air conditioning systems in cars and buildings. The Norwegian Institute for Air Research says concentrations of the gas above Mount Zeppelin doubled between 2001 and 2004.
"This gas has a warming effect on the planet more than a thousand times that of CO2"

Manufacturers of air conditioners say their systems are designed to prevent leaks. "The rapid increase shows that whatever the industry claims, the gases are not being contained," says Chris Rose of the Multisectoral Initiative on Potent Industrial Greenhouse Gases, based in London.
From issue 2571 of New Scientist magazine, 30 September 2006, page 6