Greenhouse Effect - Global Warming News Articles

New, Mean Greenhouse Gas Appears

April 11, 2000 - AP

U.S. and European researchers have discovered a greenhouse gas with frightful characteristics -- it is 18,000 to 22,200 times more powerful than carbon dioxide, and it has an atmospheric life estimated at 3,500 years.

Ole John Nielsen of the Chemical Institute at Copenhagen University presented the findings at a recent conference on greenhouse gases hosted by the Society of Danish Engineers' chemistry group. A paper has been submitted to the journal Science.

The gas, SF5CF3 -- or trifluoromethylsulphur pentafluoride -- lurks in the atmosphere between 5 and 20 miles above the Earth's surface. It was first noted in an analysis of stratospheric air samples as an unexpected reading close to SF6, or sulphur hexafluoride, a more common industrial gas.

Like SF6, SF5CF3 is a gas that can absorb heat radiating from the Earth's surface, what scientists call greenhouse gases.

Traces of SF5CF3 and SF6 were also found in deep snow in remarkably similar concentrations. SF6 concentrations have been measured for a number of years, leading the researchers to conclude that the concentration of SF5CF3 has grown from almost nothing in the late 1960s to 0.12 parts per trillion -- 10 to power of 12 -- in 1999.

Tim Wallington of the Ford Motor Company's chemical laboratories, one of the researchers, says, "... We don't know where SF5CF3 comes from, which is worrying. But it must be connected with human activity."

They think the new greenhouse gas may be a by-product of the manufacture or decomposition of SF6, an electrical insulator in transformers and similar high-voltage electrical equipment. It may derive from CF4, which is released in aluminum production.

"Most of the important greenhouse gases -- carbon dioxide, methane and nitrous oxide -- occur naturally. While we're pumping more of them into the atmosphere, there are natural processes that can remove them, allowing the atmosphere to regain its natural balance," says Vincent Gauci of the department of earth sciences and the Center for Ecology and Hydrology at Britain's Open University.

"However, this new molecule is unnatural and seems to be extremely stable, so the atmosphere has a hard time breaking it down. While it doesn't seem to be having much of an effect right now, the fact that it has such a long lifetime means that unless its production is prevented it will continue to accumulate and so may have a larger effect in the future," Gauci says.

The researchers come from the Ford Motor Company, Germany's Max Planck Institute and J. W. Goethe University, the British universities of Reading and East Anglia, the CNRS Laboratoire de Glaciologie et Geophysique de l'Environment in France, and the British Antarctic Survey.

Twentieth century 'warmest in 500 years'

Drilling down into subsurface rocks shows temperature changes over centuries

February 17, 2000 - BBC

Studies of temperature records preserved deep in underground rocks show that the Earth has been gradually warming over at least the last 500 years.

And the studies, by scientists in the US and Canada, show that the trend accelerated markedly during the 20th Century, which was the warmest of the past five centuries.

Since 1500, the Earth's temperature has increased by about one degree Celsius, with half of that increase occurring in the last century.

Trend picks up

The warming trend is speeding up

Almost 80% of the net temperature increase observed occurred in the 19th and 20th centuries.

In the Northern Hemisphere, the five-century change has been 1.1 degrees, with 0.6 recorded since 1900.

The studies, reported in the science journal Nature, are based on analysis of borehole temperatures from 616 sites on every continent except Antarctica.

The scientists lowered sensitive thermometers into holes drilled down from ground level to discover how surface temperature altered in the past. A typical borehole was measured at 10-metre depth intervals down to as far as 600 m.

Records preserved

The technique is possible because of heat conduction, which means that temperature changes at the surface generate "signals" that penetrate subterranean rocks.

The signals from short-term daily or seasonal variations penetrate only a few metres and are rapidly lost. But changes over centuries are preserved in deeper rock, although the signals travel very slowly, penetrating only about 500 metres in 1,000 years.

One of the team, Professor Henry Pollack of the University of Michigan, said: "The upper 500 metres is an archive. Like any historical archive, there are of course missing pages, and the ink has run in a few places.

"But in principle, if you drilled a borehole anywhere on a continent, you could observe a temperature profile and be able to reconstruct what had happened at that location."

The team's work involved calculating averages from all the boreholes investigated, and built on a previous analysis of borehole temperature data from 358 sites.

The scientists also compared their results with those obtained from other methods of estimating past temperature change, including studies of tree rings, ice cores, lake sediments and coral growth.

"All the methods generally show a very unusual 20th Century, and ours does too," said Professor Pollack. "It is the warmest century of the last five, and the one which is most rapidly changing."

Forecast re-inforced

"What we show that is somewhat different is that the total temperature change over the past five centuries has been greater than some of the other methods are showing."

In an accompanying article in Nature, Jonathan Overpeck, of the University of Arizona, Tucson, says the team's results re-inforce the forecast for this century: continued warming ahead.

"But they also provide unsettling indications that human alteration of the climate system over the past century will make the reliable prediction of climate change an even tougher business than expected.

"Their analysis is the latest of several to indicate that late 20th Century warming is without precedent in the past 400 to 1,000 years.

"We do not know of any combination of natural mechanisms that can explain this phenomenon. So we are left with the likelihood that human-induced global warming is under way."

And he adds a warning. "The results show yet again that the 20th Century record of climate variability is too short and cloaked with human-induced influences to provide a clear indication of natural climate variability.

"Earlier studies may have underestimated the full amplitude of natural decade-to century-scale climate variability."

Arctic expert unthaws alarming data on ice thinning

January 5, 2000 - CNN

He's an expert on Arctic ice, but he's never been to the North Pole.

Drew Rothrock says he's a "digital guy:" the sort of scientist who would rather pore over data on a computer screen than get his feet wet in the field. (Or, in the case of Arctic tundra, get his feet frozen.)

Dr. Rothrock and two colleagues from the University of Washington's Polar Research Center recently published a four-page paper in a relatively obscure journal called Geophysical Research Letters. But the findings in that brief paper won worldwide attention in media like the New York Times, Washington Post, Christian Science Monitor and CNN. Not bad for data jockeys.

Why all the attention? Turns out, Arctic ice is getting pretty thin.

Thawing decades of data

For most of the 1990s, Rothrock and his partners have been studying measurements of North Pole ice taken by U.S. Navy nuclear submarines. The Arctic Ocean is fairly deep in many places, and military submarines regularly glide beneath the ice, trying to remain strategically invisible to competing navies, while taking sonar soundings of the ice pack above. Since the end of the Cold War in 1990, the military has been increasingly willing to let scientists use their vessels, vehicles and aircraft to study the planet.

Rothock's data shows the artic ice is thinning at an alarming rate.

Arctic ice is very different than the stuff found on land, like glaciers. For starters, ice formed in seawater never gets all that thick. Most of the actual freezing takes place on the bottom of the ice sheet, where ice contacts the ocean. Ice traps air, which acts as an insulator, which eventually slows down the ice-forming process. Icebergs, by contrast, can be huge -- they are formed on land, and break off into the sea and float around.

Even in the sub-freezing temperatures of midwinter, Rothrock commonly finds Arctic ice measurements only a few inches thick, although in some places it can pile up to 10 feet or more. The Navy numbers from the '90s seemed to show a disturbing trend, however: on average, the thickness seemed to be decreasing about 4 inches (10 cm) a year.

He was wrong. The actual shrinkage left him astonished.

On average, the University of Washington team found that ice had thinned by four feet (1.3 meters) -- a 40 percent decrease since 1953. The "trend" of the 1990s seemed to be an indisputable fact.

Scientists fear Gulf Stream diversion

When Arctic ice melts, it doesn't raise the level of the ocean, and doesn't threaten coastal communities with flooding. The sea ice merely changes form when it melts. As the ice above the surface melts, its weight decreases, so it displaces less water. At the same time, the melted ice adds more water, so the ocean level remains the same.

By contrast, land-based ice does pose a threat to coastlines if it melts too dramatically.

But there is still reason to pay attention. Water from the Arctic Ocean plays an important role in Northern Hemisphere weather. The powerful Gulf Stream current moves warm water from the tropics past the east coast of the United States and Canada and northwestern Europe. If the Arctic continues to melt, some scientists fear the Gulf Stream will be diverted. Without that warm water, heavily populated areas around the northern Atlantic might suffer bitterly cold winters.

Could global warming be the cause of Arctic melting? And could that melting, ironically, make some places colder?

Rothrock won't go that far. His own theory is that a cyclical pattern of Arctic winds has stayed strong longer than expected, and that those winds have hastened the normal seasonal breakup of polar ice. He does not say -- as many environmentalists do -- that global warming is the culprit. But he also cannot say why those Arctic winds have stayed so strong.

The folks at the Polar Science Center say they need even more data. On the one hand, they are expanding their relationship with the Navy, as more and more scientists are allowed to travel on submarines and conduct experiments. On the other, they are gently pressuring the Pentagon to release even more of the mountains of Cold War data, enabling them to piece together a more complete picture of changes in ice thickness over time.

Of all the places where submarines sneak around, the statistics at one precise point are already fairly well-established. No matter what the date or the mission, the place submarines are most often given permission to surface is right at the North Pole. By tradition, the lucky sailors who are allowed to frolic at 90 degrees North play a game of softball.

Rothrock, however, doesn't care whether he ever plays in one of those games. He's content to simply analyze the numbers they bring back ... and perhaps play a digital softball game on his computer.

Ice-Age Sediment Cores Hint Climate Change On Earth Could Be Extreme

October 26, 1999 - Science Daily

An analysis of sediments from the subtropical Atlantic Ocean deposited during Earth's last glacial period indicate sudden temperature fluctuations were as large as those seen in the warming at the end of the last ice age, raising concerns about future climate change.

Scott Lehman, a research associate at CU-Boulder's Institute of Arctic and Alpine Research, said the study indicated the temperature of the Sargasso Sea between the West Indies and the Azores fluctuated repeatedly by up to 9 degrees Fahrenheit from 60,000 to 30,000 years ago.

"What is new here is clear evidence that the warm Atlantic, like the polar Atlantic, was undergoing very large and very rapid temperature changes during the last glacial period."

Instrumental climate records and models indicate changes in warm ocean temperatures are likely to produce widespread, global climate impacts, he said. The impacts are due in part to the vast surface area of Earth's warm oceans and the fact that warm oceans create much more water vapor, increasing atmospheric heat trapping.

"The temperature of the warm ocean realm regulates the water vapor content of the atmosphere and its greenhouse capacity," he said. Past temperature records and climate models suggest ocean circulation changes, like those in the last glacial period, can be triggered by human activity, showing that "the impact of possible future circulation changes may be more dramatic and widespread than suspected."

A paper on the subject by Lehman and Julian Sachs, a former CU-Boulder researcher at INSTAAR now at Columbia University's Barnard College, will appear in the Oct. 22 issue of Science, the nation's premier weekly science magazine.

Lehman and Sachs reached their conclusions after studying 50 meters of sediment cores hauled up from several miles deep in the Sargasso Sea near Bermuda by French scientists as part of an international project. The CU researchers analyzed the saturation state of organic molecules from planktonic algae over the past 100,000 years, providing sea-surface temperatures during that period.

"The warming at the end of the last ice age about 10,000 years ago was supported by the disappearance of enormous ice sheets, a one-third increase in atmospheric carbon dioxide levels and changes in the seasonal distribution of the sun's energy," Lehman said. "But the abrupt changes we documented during the last ice age seem to be almost entirely ocean driven."

Freshening of Earth's oceans is believed to have the ability to trigger abrupt and long-lasting cooling events, including ice ages, by interfering with the conveyor belt of water carrying heat from the tropics to temperate regions. "Numerical modeling studies show that similar changes can be triggered by warming associated with human emissions as well," said Lehman.

"Trapping more heat in the atmosphere has the potential to kill major parts of ocean circulation, with the effects reverberating throughout the world," he said.

A 1999 study by INSTAAR's Don Barber and colleagues showed the collapse of two gigantic glacial lakes near Hudson Bay about 8,000 years ago poured enough fresh water into the Northern Atlantic to shut down the ocean circulation for several centuries, cooling Europe and Greenland by some 6 degrees F.

The last 8,000 years have been remarkably stable in terms of climate, considering the large temperature fluctuations, said Lehman. "By altering the environment through greenhouse gas emissions, we will likely find out how fragile the stability of Earth's climate really is. We may well find out we are dealing with a hair trigger."

The next step is to determine if similar changes occurred in the much larger Pacific Ocean, said Lehman. "If so, any human-induced changes to the ocean's plumbing are likely to affect everyone on Earth, not just Greenlanders and Northern Europeans."

Hot and cold theories of global warming

July 23, 1999 - Nando Times

Sometimes global warming can result in cold weather. In a theory outlined in Thursday's issue of the journal Nature, scientists say that as the glaciers melted at the end of the Ice Age, so much cold fresh water gushed into the North Atlantic 8,200 years ago that it cooled the atmosphere for hundreds of years.

The cold spell has been well known to researchers, but its cause was a mystery.

The flood scenario demonstrates how global warming can, paradoxically, trigger a global freeze, and do it in a matter of decades.

If a modern glacier such as the Greenland Ice Sheet melts as a result of rising temperatures in the next century, it could trigger a similar flood and climate fluctuation, researchers said.

The study by University of Colorado and Canadian researchers examines evidence of a huge flood in the Hudson Bay region of Quebec and Ontario.

The Laurentide Ice Sheet covered parts of North America with ice up to 2 miles thick for more than a million years. As it retreated toward the poles, the ice sheet left in its wake at least two lakes containing more water than the Great Lakes combined.

In the Hudson Bay, ice held the water in place like a plug in a bathtub. But when the plug finally melted, trillions of gallons gushed into the Labrador Sea, shooting out at 100 times the rate water leaves the Mississippi.

Independent research showed the temperature dropped significantly within several hundred years of the flood. But nobody could pinpoint if these two events were connected, said the study's lead author, University of Colorado geologist Don Barber.

The evidence linking the temperature drop to the flood includes radiocarbon dating of clams in the flood sediment.

The Atlantic Gulf Stream normally acts like a conveyor belt to deliver warm tropical water to temperate regions. By adding so much fresh water in such a short time, the flood shut down the Gulf Stream, Alley said.

Temperatures in Greenland and Europe dropped by 6 to 15 degrees for at least 200 years, according to ice core data.

Study finds small temperature can disrupt ecosystems

Paul Recer - AP - Washington - March 26, 1999

A temperature change of only a few degrees can disrupt a community of animals, according to a researcher who studied how hot and cold affects the delicate balance of starfish and mussels in Oregon's tidal waters.

Eric Sanford of Oregon State University said his study, published today in the journal Science, suggests that if a key species in a community of animals is particularly sensitive to temperatures, a slight warming or cooling can start a whole cascade of rapid changes affecting every animal in an ecosystem.

Sanford said in an interview that he found a 5-degree change in temperature is enough to change dramatically the feeding habits of the starfish, a five-armed creature that feeds mainly on mussels and is common along the Pacific coast of the United States. The finding, said Sanford, has important implications for understanding the effects of global warming.

``Many people have assumed that the effects of climate change would be gradual,'' the researcher said in an interview. ``But this shows that if an important species in a community is highly sensitive to temperature, then the effects of a small temperature change can happen rapidly.''

In his study, Sanford tracked the feeding patterns of starfish kept in the laboratory at different temperatures. He checked his results by manipulating the population of starfish and mussels in two areas along the Oregon coast. Sanford found that a temperature drop of 5 degrees caused the starfish to virtually stop feeding on the mussels. This allows the mussels to rapidly expand in population. Conversely, when the water temperature was increased by 5 degrees, Sanford said starfish went on a feeding binge, quickly reducing the population of mussels. Either way, he said, there are dramatic changes in the tidal community of animals.

When mussels are not controlled by starfish, said Sanford, their population explodes. The mussels attach themselves to every surface in the near-shore tidal zone, crowding out barnacles, algae and other organisms.

When starfish eat too much, he said, the reef-like mussel communities quickly start falling apart. These reefs, Sanford said, are homes for crab, sea cucumbers and worms, all important parts of the ecosystem.

Temperatures along the Oregon coast are affected by upwelling, cold deep waters surging to the surface. The frequency of upwellings, said Sanford, is determined by winds that, in turn, are affected by global temperatures.

If cold upwellings become less frequent, starfish may eat more mussels, said Sanford; if the upwellings happen more often, thus cooling the tidal waters, starfish will eat less, allowing the mussel population to suddenly explode.