"Superweeds" are plaguing high-tech Monsanto crops in southern US states, driving farmers to use more herbicides, return to conventional crops or even abandon their farms.

The gospel of high-tech genetically modified (GM) crops is not sounding quite so sweet in the land of the converted. A new pest, the evil pigweed, is hitting headlines and chomping its way across Sun Belt states, threatening to transform cotton and soybean plots into weed battlefields.

In late 2004, "superweeds" that resisted Monsanto's iconic "Roundup" herbicide, popped up in GM crops in the county of Macon, Georgia. Monsanto, the US multinational biotech corporation, is the world's leading producer of Roundup, as well as genetically engineered seeds. Company figures show that nine out of 10 US farmers produce Roundup Ready seeds for their soybean crops.

Genetically engineered crops do little to improve yields and instead promote the proliferation of herbicide-resistant weeds that actually curb production, according to a study by the Union of Concerned Scientists.

Corn and soybeans modified to resist insects and the herbicide glyphosate haven't been proven to boost yields, the Cambridge, Massachusetts-based group says in a 44-page report. The modified plants have increased the number of glyphosate-resistant weeds that compete for soil nutrients and moisture, reducing production, the group says.

A strong undersea earthquake with a preliminary magnitude of 6.4 jolted the far north of Japan and Russia's far east early on Sunday, a Japanese government agency reported, but there were no immediate reports of damage.

There was no threat of tsunami from the quake at 4:19 a.m. (1919 GMT). It centred in the remote and sparsely populated Kuril Islands northeast of Hokkaido, the Japan Meteorological Agency said on its website (www.jma.go.jp).

A strong 6.2-magnitude quake struck in Indonesia's north Sulawesi province on Sunday but there were no reports of damage or injuries, the geophysics agency said. The quake hit at 1.23pm about 20 kilometres (12 miles) north-east of Melonguane city at a depth of 50 kilometres.

No tsunami alert was issued.

'Tremors are felt in the area but not significant ones. There's no report of damage,' agency official Suharjono told AFP.

Russian sea captain Dimitri Zinchenko has been steering ships through the pack ice of Antarctica for three decades and is waiting to see evidence of the global warming about which he has heard so much.

Zinchenko's vessel, the Spirit of Enderby, was commissioned in January last year to retrace the steps of the great Antarctic explorer Ernest Shackleton, marking the century of his Nimrod expedition of 1907-09.

Spirit of Enderby was blocked by a wall of pack ice at the entrance to the Ross Sea, about 400km short of Shackleton's base hut at Cape Royds. Zinchenko says it was the first time in 15 years that vessels were unable to penetrate the Ross Sea in January. The experience was consistent with his impression that pack ice is expanding, not contracting, as would be expected in a rapidly warming world. "I see just more and more ice, not less ice."

Two of the Arctic ice sites show April 16 ice at recent record levels. The Japanese site IJIS has a seven year April record going back to 2003, and reports 2009 levels at the highest extent on record for the date: 13,649,219 km2.

The Danish Meteorological Institute has a five year database, and also shows April 16 ice extent as the highest in their short record.

Ice is expanding in much of Antarctica, contrary to the widespread public belief that global warming is melting the continental ice cap.

The results of ice-core drilling and sea ice monitoring indicate there is no large-scale melting of ice over most of Antarctica, although experts are concerned at ice losses on the continent's western coast.

Antarctica has 90 per cent of the Earth's ice and 80 per cent of its fresh water. Extensive melting of Antarctic ice sheets would be required to raise sea levels substantially, and ice is melting in parts of west Antarctica. The destabilisation of the Wilkins ice shelf generated international headlines this month.

However, the picture is very different in east Antarctica, which includes the territory claimed by Australia.

East Antarctica is four times the size of west Antarctica and parts of it are cooling. The Scientific Committee on Antarctic Research report prepared for last week's meeting of Antarctic Treaty nations in Washington noted the South Pole had shown "significant cooling in recent decades".

Australian Antarctic Division glaciology program head Ian Allison said sea ice losses in west Antarctica over the past 30 years had been more than offset by increases in the Ross Sea region, just one sector of east Antarctica.

Denver - Hundreds of stranded travelers resumed their journeys Saturday after spending the night at shelters when a powerful spring storm walloped the Rocky Mountains and foothills west of Denver with more than 3 feet of snow.

Officials reopened an 80-mile stretch of Interstate 70 between Golden and Vail that had been closed Friday, said Colorado Department of Transportation spokesman Bob Wilson. Drivers were cautioned to expect heavy traffic and sloppy road conditions.

"It's not the I-70 you know in a June afternoon," Wilson said.

Storm warnings were dropped as the bulk of the storm moved east into Kansas.

About 15,000 homes and businesses were without power in Denver and areas north and west of the city. The heavy snow had weighed down power lines and tripped system circuit breakers. Piles of snow and closed roads were preventing crews from reaching some areas, Xcel Energy spokesman Joe Fuentes said, adding that crews hoped to restore power by 11 a.m. Sunday.

The study, being published Thursday in the journal Nature, suggests that a sudden rise of 6.5 feet to 10 feet occurred within a span of 50 to 100 years about 121,000 years ago, at the end of the last warm interval between ice ages.

"The potential for sustained rapid ice loss and catastrophic sea-level rise in the near future is confirmed by our discovery of sea-level instability" in that period, the authors write.

Yet other experts on corals and climate are faulting the work, saying that big questions about coastal risks in a warming world remain unresolved.

Among the most momentous and enduring questions related to human-caused global warming are how fast and how high seas may rise. Studies of past climate shifts, particularly warm-ups at the ends of ice ages, show that fast-melting ice sheets have sometimes raised sea levels worldwide in bursts of up to several yards in a century.

A question facing scientists is whether such a rise can occur when the world has less polar ice and is already warm, as it is now, and getting warmer.

Citing the evidence from fossil coral reefs, the authors of the new study say with conviction that the answer is yes.

The study focuses on a set of fossil reef remains exposed in excavations for channels at a resort and water park, Xcaret, about 35 miles south of Cancún on the east coast of the Yucatán Peninsula.

On these taxing days, when we become a defiantly bipartisan nation of whiners convinced that we are handing over to the Internal Revenue Service our blood and sweat and mother's milk, our pound of flesh and firstborn young, maybe it's time for a little perspective.

Legions before us have donated all these items and more to the public till, and not just metaphorically speaking, either. Benjamin Franklin was right to equate paying taxes with a deeply organic behavior like dying. It turns out that giving up a portion of one's income for the sake of the tribe is such a ubiquitous feature of the human race that some researchers see it as crucial to our species' success. Without ritualized taxation, there would be precious little hominid representation.

Moreover, plenty of nonhuman animals practice the tither's art, too, demanding that individuals remit a portion of their food, labor, comfort or personal fecundity for the privilege of group membership. And just as the I.R.S. depends on threat of audit as much as it does on anybody's sense of civic responsibility, so do other toll-collecting species ensure compliance by meting out swift punishment against tax cheats. For example, Marc Hauser of Harvard University has found that when a rhesus monkey is out foraging and comes upon a source of especially high-quality food, like, say, a batch of ripe coconuts, the monkey is expected to give a characteristic food call to alert its comrades to the find. "The bad thing about doing a food call is that it means others will come and take some of the food," said Laurie R. Santos, who studies the primates at Yale University. Yet a monkey who opts to keep mum about its discovery could face worse. Should other group members happen by while the private feast is under way, they will not only claim the food for themselves, but the most dominant among them will also beat the cheater indignantly.