Sure, here ya go:
December 19, 1999
1999 Continues Warming Trend Around
Globe
By WILLIAM K. STEVENS
At the New York Botanical Garden in the Bronx, fragrant white
blooms with a pink blush are breaking out on specimens of a
popular landscaping shrub called the Koreanspice viburnum -- four to
five months early. Snowdrops, among the earliest bulbs to send up
shoots when winter ends, have already poked up their noses. In some
New York suburbs, yellow forsythia blossoms have brought a premature
touch of spring to December.
"There's a little confusion out there," said Wayne Cahilly, an arborist at
the botanical garden, and he expressed no doubt as to the reason:
abnormal warmth. Or is it so unusual? "I think this warm weather is
becoming normal," Mr. Cahilly said.
Certainly it seems that way of late. Last month was the warmest
November in 105 years of record-keeping in the contiguous 48 states,
and the fourth-warmest in the Northeast. The trend continued into
December in most of the country; as of Friday, the average temperature
for the month in New York, for instance, was 5.7 degrees Fahrenheit
above normal.
But that is almost the least of it. Federal scientists reported last week that
in the contiguous 48 states and on other global land masses, including
Europe and Asia, 1999 is certain to join 1998 as one of the two warmest
years on record, continuing a long-term trend toward a warmer climate.
The trend has been especially sharp in the last quarter of the 20th
century. Since the mid-1970's, the scientists reported, the average global
surface temperature has increased at a rate of about 3.5 degrees per
century -- about the same rate estimated for the 21st century if emissions
of waste industrial gases that trap heat in the atmosphere are not
reduced.
By comparison, the world has warmed by 5 to 9 degrees since the
depths of the last ice age, 18,000 to 20,000 years ago.
Globally, this year is turning out to be slightly less warm than the record
year of 1998, the scientists said, because of the general cooling influence
of the phenomenon known as La Ni¤a, a great pool of cool water that
develops naturally from time to time in the eastern tropical Pacific.
Because of a cooler ocean surface than last year's, the average global
surface temperature in 1999 is not expected to reach the 1998 record of
about 58 degrees; it will probably rank as the fifth-highest reading since
1880. Nevertheless, a planetary heating trend that made the 1990's the
warmest decade on record is continuing.
La Ni¤a's counterpart, the pool of extra-warm Pacific water called El
Ni¤o, imparted an extra shot of warmth in 1998, and the global
temperature had been expected to drop off this year. But despite La
Ni¤a's coolness, the temperature of the Northern Hemisphere's land
masses is turning out to be the second-highest ever recorded.
At 55.7 degrees, for instance, this year's average temperature in the 48
states is projected to fall just shy of a record 56.4 degrees set in 1998.
The projected 1999 average global land temperature is 56.9 degrees,
1.42 degrees above the average for the years 1880-1998. The warming
was especially pronounced in Europe, Asia and North America. In June
and July, for example, Russia experienced one of its longest heat waves
of the century.
Thomas R. Karl, the director of the National Climatic Data Center in
Asheville, N.C., which reported the latest figures, said he was surprised
at the persistent warmth on land in a La Ni¤a year. "We haven't seen
anything like this in the observed temperature record," he said.
Apart from their broad effect on global temperatures, La Ni¤a and El
Ni¤o also change patterns of atmospheric circulation, with strong
short-term effects on weather around the world. Last winter, largely
because of La Ni¤a, the Eastern United States had highly variable
weather, with stretches of warmer-than-normal temperatures punctuated
by sharp bouts of cold. Over all, warmth dominated. But it was snowier
and colder than normal in the Pacific Northwest and the Great Lakes.
A similar pattern is forecast for this winter, but there is a wild card:
Although it is too early to tell, federal experts say that if atmospheric
conditions in the North Atlantic develop in a certain way, the
mid-Atlantic coast, including the New York region, could see some
heavy snow.
The experts say that later next year, other natural fluctuations in
circulation could bring a repeat of last summer's drought in some parts of
the country, including the Middle Atlantic region and the Northeast, as
well as a more active hurricane season.
Underlying these natural machinations of atmospheric behavior -- and
possibly modifying them in ways not yet clear to scientists -- is a
centurylong global warming trend. The average global surface
temperature has risen by more than 1 degree Fahrenheit in the last
century, according to the federal experts. The dominant scientific view is
that emissions of heat-trapping atmospheric gases like carbon dioxide,
produced by the burning of coal, oil and natural gas, are at least partly
responsible.
But in the last quarter-century, the rate of warming has been more than
double that of the 20th-century average. Mr. Karl's group reported last
week that since the mid-1970's, the global temperature has risen at a rate
of about 0.35 degrees per decade, or 3.5 degrees per century. Scientists
predict that the planet will warm by 2 to 6 degrees over the next 100
years (the best estimate is 3.5 degrees) if emissions of the heat-trapping
gases are not cut.
A warming of 3.5 degrees, according to experts, would cause
widespread climatic and environmental dislocations, producing more
extreme weather, raising the global sea level, causing precipitation
patterns to change and shifting climatic and agricultural zones.
The United States experienced record-breaking warmth in both of the
two most recent winters, said scientists at the government's Climate
Prediction Center in Camp Springs, Md. The center predicted last week
that on average, most of the country would be warmer than normal over
the January-through-March period just ahead.
In the winter of 1997-98, circulation patterns influenced by El Ni¤o
played a crucial role in the warmth. Last winter, different circulation
patterns associated with La Ni¤a had a similar effect. Both La Ni¤a and
El Ni¤o modify North America's climate by changing the position of the
jet stream, the high-altitude river of air that generally runs from west to
east and marks the boundary between cold northern air and warm
southern air.
In a La Ni¤a winter, the jet stream typically plunges down through
Montana and the northern Plains and then into the central part of the
country before curving northeastward. This curve would normally take
place in the East, but in a La Ni¤a year it tends to take place farther
west, leaving the Eastern Seaboard on the warm side of the warm-cold
division marked by the jet stream.
Eventually this whole pattern drifts eastward, bringing cold weather to the
East. An influx of cold northern air is in fact expected for the latter part of
this month in the Northeast, said Fred Gadomski, a meteorologist at
Pennsylvania State University. This progression happens repeatedly.
Sometimes in a La Ni¤a regime, the course of the jet stream temporarily
flattens out and whisks warm Pacific air all the way across the continent.
Mr. Gadomski said he would not be surprised if such a nationwide warm
spell developed after the upcoming cold snap passes.
Other factors, too, are shaping the winter, scientists at the prediction
center say. In addition to the general warming of the atmosphere, for
instance, year-to-year flip-flops in circulation patterns over the North
Atlantic can have a major effect on weather in the Eastern part of the
country.
If this so-called North Atlantic oscillation is in one mode, typified by low
atmospheric pressure over the ocean, the East tends to be warm. If high
pressure dominates, said Vernon Kousky, a research meteorologist at
the prediction center, the jet stream tends to follow a southerly course
into the ocean in the vicinity of Virginia and North Carolina. North of
that, big snowstorms can develop, Mr. Kousky said, as happened in
1995-96, a La Ni¤a winter in which a January blizzard dropped record
snows from Washington to New York, essentially shutting down the
nation's capital for days.
The North Atlantic oscillation's effect "never makes itself felt till the end
of December or early January," Mr. Kousky said, adding that forecasters
at this point cannot predict its behavior this winter.
A similar oscillation in the North Pacific may influence next summer's
American weather, he said. The sea-surface temperature there flips back
and forth between warm and cool states similar to those of El Ni¤o and
La Ni¤a, but stays in one phase for several years. Researchers believe
that it may recently have flipped into its warmer state. If it has, Mr.
Kousky said, it could set off atmospheric chain reactions next summer
that will bring a repeat of last summer's drought in much of the country's
Northeastern quadrant, as well as a more active Atlantic hurricane
season.
"We're trying to alert people to that possibility," he said.
Last summer's drought established records for dryness in the Northeast,
the Middle Atlantic and the Ohio Valley, Mr. Karl's group reported last
week. The April-to-July period was the driest or second-driest in all
states from West Virginia to Maine. The drought was followed by record
rainfall as hurricanes Dennis and Floyd struck the East Coast. Intensified
drought and heavier rain are both expected to result from global
warming, although no particular weather event of any kind can be
attributed to it.
Copyright 1999 The New York Times Company |
