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From April 8, 2007, News-Sentinel


A motorist on Gill Avenue gets assistance Christmas Day 1976, which according to Dale Kaiser, a scientist at Oak Ridge National Laboratory, was the last time Knoxville saw snow on Dec. 25. His studies show that since the 1960s, a decade when the city had four white Christmases, each decade’s snowfall has decreased.



Patrick Mulholland, an Oak Ridge National Laboratory aquatic ecologist, checks equipment where weather data is collected at a clearing on top of the Walker Branch Watershed. He leads the study, which he says is the longest and most involved of watershed studies in the United States.

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Dogwoods to frogs, tulips to snow, Knox shows signs of warming

By BRAD WILLIAMS, williamsbr@knews.com
April 8, 2007

In the 1960s, Knoxville had four white Christmases.

In 1976, it had one, but there have been none since, according to Dale Kaiser, scientist at Oak Ridge National Laboratory's Carbon Dioxide Information Analysis Center.

Kaiser studied four decades of Dec. 25 snow reports in 16 cities, finding 1-inch snows have decreased.

It's not just Christmas Day, though. Since the '60s, each decade's snowfall in Knoxville has decreased.

Kaiser didn't look for causes, but signs that range from singing frogs to warming watersheds indicate our area weather is changing.

And on a global scale, an international body of scientists and many others agree: Global warming is here.

Tougher time for tulips

In 1990, Knoxville was in plant hardiness Zone 6, according to The National Arbor Day Foundation.

Knoxville is now in hardiness Zone 7, a zone where more southern trees and shrubs flourish. The zone shift can be seen all across the northern half of the state.

It effectively means plants that once had difficulty growing here are now finding it easier to thrive, said Lisa Stanley, master gardener at Stanley's Greenhouses, 3029 Davenport Road.

One example is autumn sage.

"Twelve years ago, we were saying, 'Be careful with these,' " Stanley said.

Now she has some that are 12 years old. Pineapple sage, encore azalea and Confederate jasmine are others Stanley has succeeded with, despite traditional concerns that the area gets too cold.

She said she's been trying plants that were thought to fare better farther south and realizing they grow without a problem.

"We've been warming up for a while."

But that's also becoming a problem for some plants, like tulips. Stanley said tulips need 14 to 16 cold-weather weeks to present a nice bloom.

"With the way our winters have been, that's one reason why it's been harder to grow your better tulips," she said.

Local temperatures

Scientists say global warming doesn't mean some areas won't cool. The heat won't distribute evenly, as the poles take the brunt.

While nothing sure can be said about Knoxville — smog may have a cooling effect, too — there are clues pointing to global warming.

ORNL aquatic ecologist Patrick Mulholland leads a study of the Walker Branch Watershed in Oak Ridge, "one of the longest and most involved watershed studies in the U.S.," he said. "We have observed a statistically significant warming trend."

Mulholland said it translates to a 2.3-degree Fahrenheit increase in average annual air temperature from 1969 to 2006.

"Interestingly enough, the winter temperature, January through March, has gone up even more sharply," Mulholland said, adding the trend is not inconsistent with global warming models.

Mulholland said studies show spring is earlier and fall is slightly later, so the growing season in the Northern hemisphere is expanding.

Blooms, birds and frogs

A survey last March called "Season Creep" — released by Washington, D.C.-based Clear the Air and experts from Tennessee and other states — noted lilacs and honeysuckle blooming six days early, frogs starting mating season 12 days early and Northern cardinals singing 22 days early.

Lyn Bales, marketing director and naturalist at Ijams Nature Center, isn't surprised.

After searching an Ijams trail on March 8, Bales said: "Three native wildflowers are up and blooming: yellow trillium, cut-leaved toothwort and bloodroot. All somewhat early, considering this is the first week of March."

Bales also said frogs are hopping. He heard spring peepers and chorus frogs on his walk.

They become lethargic in the cold but appear whenever it warms.

"We hear frogs earlier," Bales said. "I'm sure I heard them a day in January."

Unfortunately for birds that migrate by length of day instead of temperature, warming brings out food before they arrive.

"Now the leaves and caterpillars are coming out earlier than the birds return," Bales said. That could mean birds aren't fattening up as they should.

Latest data

According to the Intergovernmental Panel on Climate Change, or IPCC, global warming is happening now. The panel was assembled in 1988 by the World Meteorological Organization and the United Nations Environmental Programme.

"Warming of the climate system is unequivocal, as is now evident from observations," said the IPCC's Working Group I report, released Feb. 2.

The report said there's "at least a 90 percent probability" humans have been the main cause since 1950.

"Eleven of the last 12 years (1995-2006) rank among the 12 warmest years in the instrumental record of global surface temperature (since 1850)," according to the report.

Greenhouse gas concentration has spiked so quickly that it fits no pattern seen over thousands of years, essentially proving that the current rise is the result of human activity, the IPCC argues.

A follow-up IPCC report, released Friday from a second working group, goes farther: It projects specific temperature increases and their effects, such as more species going extinct and more people who may starve or face water shortages or floods.

Some scientists are calling this degree-by-degree projection a "highway to extinction."

The final document was the product of a United Nations network of 2,000 scientists as authors and reviewers, along with representatives of more than 120 governments as last-minute editors.

Don't some disagree?

John Christy, professor and director at the Earth System Science Center at the University of Alabama in Huntsville, was a contributor for the IPCC and a lead author of its 2001 report.

"To say that 800 contributing authors or 2,000 reviewers reached consensus on anything describes a situation that is not reality," he said in a recent statement to Congress.

Some scientists believe threats are worse than the IPCC describes, but Christy said a minority of scientists disagrees.

"We haven't (east of the Rockies) had anything like what we had in the '30s and '50s in terms of heat and drought," Christy said. "We see some warming, but not the extent that people are being scared about."

Christy checks climate models against past data. He says models have problems, pointing to the fact that they predicted temperatures in the Southeast would rise over the last century. They slightly fell.

Temperatures rose in the United States as a whole, though, and they have in Tennessee since the '60s.

One of Christy's mainstay arguments is that the danger of CO2 increase is exaggerated and other causes of warming, like heat-absorbing concrete, should assume more blame. He says cutting CO2 emissions won't achieve the desired ends.

Scientists who say humans significantly contribute to climate change include those at the Environmental Protection Agency, the American Meteorological Society, the American Geophysical Union, the National Wildlife Federation, the Union of Concerned Scientists and the National Academy of Sciences.

What could happen?

Stephen Smith, executive director of the Knoxville-based Southern Alliance for Clean Energy, said global average temperature is up about 1.4 degrees Fahrenheit.

"There is a developing consensus that we want to limit this warming," Smith said. "You don't want to get more than 3.5 degrees of additional global average temperature increase locked in."

Unfortunately, even if all warming activities stopped today, Smith says warming won't stop immediately. The ocean stores heat, which doesn't get felt until later. Smith said the IPCC estimates 0.9 degrees is "in the pipe," boosting warming that's now unstoppable to 2.3 degrees — and putting Earth close to a dangerous threshold.

Smith says as we approach and cross this threshold, "we're going to see things that we've never seen before, and some of the changes could be irreversible."

While slow, natural cycles let ecosystems adapt, humans may turn up the thermostat too quickly.

"Warmer climates get heavy precipitation events more frequently than cooler climates," said researcher Anthony Arguez with the Asheville, N.C.-based National Oceanic and Atmospheric Administration. "If temperatures continue to warm, this can have serious impacts on transportation, agriculture, ecology and urban development."

Some say drought will increase because soil retains less moisture when rain falls quickly and runs off. Plus, the heat speeds evaporation.

Winters kill down the numbers of fleas, ticks and other pests. A warmer, wetter world promises mosquitoes galore.

Look to the dogwoods

One spring bellwether in the South has always been dogwoods. And a perennial fret in Knoxville has been: Will the trees be in bloom by the time the Dogwood Arts Festival wraps up?

"It used to be everyone kept their fingers crossed that they would be blooming for the festival," Bales said.

In late March, two weeks before the festival, the blooms had already arrived.

Brad Williams may be reached at 865-342-6432.

Copyright 2007, KnoxNews, All Rights Reserved.
Mirrored with permission