Human fingerprint seen on climate change
The announcement mid-August, in the midst of another week of hot, hazy and humid weather, that July was the seventh consecutive month in 1998 to set a new world temperature record probably wasn't a surprise to most Ontarians. After all, like most of North America, Ontario had just posted the warmest first half of the year (almost three degrees warmer than normal) since across-the-country climate record keeping began in Canada more than 50 years ago.The heat of the first part of 1998 follows immediately on the heels of the world record-breaking year of 1997. In fact, the 10 warmest years on record have now occurred since 1983. Furthermore, studies into past climates indicate that the 20th century has been the warmest of at least the last six centuries. The planet is definitely becoming warmer.
But why? Is this finally hard evidence of human interference with the world's climate? Or is this simply earth's response to periodic changes in the sun's energy. Information from Greenland's ice cores, for example, suggests that several "little ice ages" have occurred quite naturally from time to time over the past 10,000 years, apparently linked to small fluctuations in incoming solar energy. About 600 years ago, another such cooling began, peaking in about 1600 AD, just when the number of sunspots visible on the sun's surface was at a minimum. Might the warming of the past century, and particularly the past few decades, therefore simply be a result of a more active sun?
Researchers have been studying sun-climate connection for decades. However, any good agreement between the sun's sunspot behaviour and the earth's climate that emerged from these studies seldom seemed to persist for more than a few decades at a time. Furthermore, no one had yet come up with a good explanation as to how very small changes in incoming solar energy (at most a few tenth's of a percent) could cause such significant changes in climate.
During the past few years, several research projects have thrown new light on the debate. Scientists have recently noted that most of the changes in incoming sunlight happen in the ultraviolet, not the visible part of the energy. Changes in ultraviolet radiation could in turn affect the concentration of ozone in the upper atmosphere, which in turn alters temperatures and changes the air currents of the atmosphere. Meanwhile, Judith Lean - a researcher working at the U.S. Naval Research Laboratory - and colleagues discovered a very good agreement between average Northern Hemisphere summer temperatures and decade-to-decade changes in the intensity of incoming sunlight (both reconstructed from chemical analysis of tree rings, ice cores and other sources of historical climate information). In fact, between 1600 and 1800 the solar fluctuations explained about 75 per cent of the changes in the hemisphere's summer temperatures.
Using the equation that best described this agreement, Lean and her colleagues then projected how changes in incoming solar energy since 1800 might have affected temperatures. When they compared their predictions with actual observations, they found that the sun appears to have been an important factor in the warming of the past century. However, the results also clearly suggest that the sun was not the only factor. While about 50 per cent of the warming during the entire century could be explained by the increase in the sun's energy, less than a third of the rapid warming since 1970 could be linked to this increase.
Climatologists in general agree that this is further evidence that recent changes in temperature may in part be due to the rising concentrations of greenhouse gases in the atmosphere. In other words, the human fingerprint on the climate system is becoming more visible.
The results of the study by Lean and others still have
significant
uncertainties that need to be resolved. Future research may show
that the
role of the sun in recent climate trends may have been
exaggerated - or
underestimated. However, the presence of the human factor in at
least the
last few decades appears to be almost certain. If this conclusion
holds
(and there are good reasons to suggest it will), then the record
global
temperatures of the 1980s and 1990s are likely to soon give way
to even
higher temperatures as a new millennium dawns.
Maybe that air conditioner doesn't sound like such a bad idea
after all.
Henry Hengeveld is a science adviser on climate change,
Environment Canada
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UNEARTHED
Notes from All Over
Emu wrestling, meat for health
Busily messing up farm drainage, Canada's national rodent generally gets more curses than credit from your average farmer.
Not, however, in Atikokan, Ont., where beavers are being hailed for restoring the water supply to 3,800 residents.
David Lindsay, who runs an aquaculture operation near Atikokan, halfway between Thunder Bay and Fort Francis along the Minnesota border, reports that the town's water supply ran dry after prolonged drought this summer caused the source, the Atikokan River, to drop to six inches deep.
To look at the map, the region has more lakes than land. In past shortages, the dams in surrounding lakes were used to release water. Lindsay says that due to government cutbacks, they fell into disrepair and were ultimately removed. As a result, the town ran out of water, despite having built a modern multi-million-dollar water plant several years ago.
Coming to the rescue in the end were the free-market-minded beavers, who had continued damming away despite the lack of government handouts. Lindsay says getting the town's taps flowing again was simply a matter of wrecking some of their handiwork.
The RCMP nabbed an unusual escapee in Langley, B.C. during the
summer. An
errant emu spent several hours wreaking havoc on the streets of
the
Vancouver suburb before being wrestled by RCMP officers and an
animal
control officer, reported the Toronto Star.
"The little things are a lot stronger than people say they are," said one RCMP constable. "The legs are just lethal, and they have claws as big as my thumb."
Neither the bird nor any officers were injured in the capture, though motorists were forced to swerve around the emu as it trotted throughtraffic . Thought to have escaped from an area emu farm, the bird was locked up in an animal shelter for its own protection.
Red meat and and cheese - maligned for their fat content by
healthful
eating advocates - are being touted for the disease-prevention
qualities of
a compound found in both.
A polyunsaturated fatty acid called conjugated dienoic linoleic acid (CLA) - naturally occuring in red meat and cheese, and to a lesser extent in milk, yogurt, poultry and eggs - has inhibited the spread of skin cancer in mice and prevented the onset of diabetes in rats, at least in the short term, reports Purdue News.
The research - by Purdue University professor of foods and nutrition Martha Belury, Purdue colleagues and others at Penn State - found that heating food, like pan-frying meat, increases CLA content. CLA inhibits cancer in part by activating hormone receptors called PPARs, or peroxisome proliferator-activated receptors.
The diabetes research suggests CLA can help prevent adult-onset
diabetes
by helping "reduce blood glucose levels," says Belury. "[CLA]
looks just
like corn oil, but maybe just a little bit clearer. It is in
foods normally
associated with saturated fats, but those foods can contain
things that are
good for you, too. The lesson here is that we still know so
little about
what is in foods naturally."
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