March 27, 2006
Global Warming Speeds Up Arrival of Spring
The sun still crossed the equator on March 20th marking the vernal equinox and the official start of spring, but Mother Nature is increasingly getting a jumpstart on the celestial movements. Over the last 150 years, scientific measurements show that events signifying the beginning of spring have all shifted.
These events now happen about a week earlier on average in the northeast United States, according to a new report, Evidence of Early Spring, from the group Clean Air-Cool Planet (CA-CP), which today announced the new, first day for "natural spring," March 13. The group, along with University of New Hampshire climate scientist Cameron Wake, Tim Flannery, author of the book The Weather Makers, and professor David Wolfe of Cornell University, conducted a call-in press conference today to discuss the issue and announce spring's new "arrival."
"Of course, the sun will still cross the equator on the 20th, marking the vernal equinox, but biological spring has changed due to global warming and that's threatening to put ecosystems badly out of synch," Markham said.
Evidence of Early Spring follows a comprehensive report issued collaboratively in March 2005 by CA-CP and Wake entitled Indicators of the Climate Change in the Northeast, which looked at 11 different physical and biological markers of the changing climate in the region.
Indicators of the Climate Change in the Northeast noted that the average Northeast winter temperature has increased 4.4 degrees Fahrenheit from 1970 to 2000. During that same period, the growing season increased by 15 days and days with snow on the ground decreased by 16. For the coastal parts of the region, sea surface temperatures and levels have also risen.
"Climate researchers had known for some time that various trends were emerging in the long-term data sets for things like temperature, precipitation, days with snow on the ground, length of growing season, as well as bloom dates," said Wake, a research associate professor at the Climate Change Research Center in UNH's Institute for the Study of Earth, Oceans and Space.
"Working with researchers from Cornell, US Geological Survey, and others, we've been able to bring this data together in one place for the first time, and analyze it for consistent trends." Although the report states that climate has always changed and always has will, what is unique in modern times is that "human activities are now a significant factor causing climate to change." The report points out that while it cannot be conclusively proven from the data that all of the regional warming is due to human actions, "the warming is fully consistent with what we would expect from global warming caused by increasing greenhouse gas concentrations."
What the data shows, says Markham, is that things are changing rapidly in the Northeast, and changing along the lines projected by various global models of climate change resulting from global warming. The clearest signal, he says, is the shift in late winter and early spring conditions.
"Many of the indicators associated with end-of-winter or the beginning of the growing season show very uniform movement "“ about a week "“ earlier. This is consistent with predictions, and it is scientific evidence that we don't need to wait decades or years to see dramatic climate change "“ it's happening all around us right now," Markham says.
The following indicators show average changes as noted:
* Growing season: 8 days longer (1874 "“ 2001)
* Spring bloom: 4 "“ 8 days earlier (1965 "“ 2005)
* High-volume spring river flow: 7 "“ 14 days earlier (1936 "“ 2000)
* Lake ice-out: 9 "“ 16 days earlier (1807 "“ 2000)
* Days with snow on the ground: 16 fewer days (1970 "“ 2001)
One of the contributors to the indicators report, Dr. David Wolfe from the Horticulture Department at Cornell University, collected biological data on bloom dates for apples, grapes, and lilacs.
"Collectively, analyses for the northeastern U.S. indicate that, on average, lilacs are blooming about four days earlier, and apple and grapes are blooming about eight days earlier than they were half a century ago," Wolfe noted in his report, while cautioning that the earlier start to the growing season indicated by the data may not be a good thing.
"Farmers may tend to look at this and say that it's good, because they will get an earlier yield. But earlier bloom dates make these species more susceptible to damage from frost," he said, "and analysis of data on apple yields indicates that warmer temperatures from January 1 to bud break correlated with lower yields, not higher."
Wolfe also reported that the magnitude of the impact of earlier bloom dates on woody perennials in the Northeast "is similar to that reported for bloom of other plant species, and for bird and insect spring migration arrivals, by researchers in other parts of the U.S. and Europe." He said findings are also "qualitatively in agreement with reports of earlier spring "Ëgreen wave' advancement in the northern hemisphere based on satellite imagery of vegetative cover," both observations supporting the findings.
Markham said these indicators are ominous for some species, based on research done in Britain and beginning to be done here.
"It's becoming startlingly clear from scientific studies around the globe that the early onset of spring activity is one of the distinctive fingerprints of climate change," according to scientist and author Tim Flannery, director of the South Australian Museum and a professor at the University of Adelaide. Flannery, author of The Weather Makers: How Man Is Changing the Climate and What It Means for Life on Earth, which chronicles changes already occurring from global warming, added "In the northeastern US, as in other parts of the planet, ecosystems face dramatic disruption as seasonal rhythms change as a result of global warming." Studies show that for species whose migration, for instance, is triggered by length of day, and so arrive at their warmer-weather homes at the same time each year, there is now occurring a "Ëmismatch' with traditional food sources, including insects and plants.
"The larval stages of insects, for example, are often controlled by temperature, so the caterpillar the birds have fed on for centuries may now be a butterfly before the birds get there. The result," Markham said, "is a decline in reproductive success for the birds "“ and a plague of the insects. It may now be the case that because of global warming, the early bird no longer gets the worm."
Markham noted that we don't know "where this kind of interference with the climate system will lead us. But we have already begun to see disruptions in traditional economies like maple sugaring and ski tourism, and it's likely these are harbingers of major disruptions to come."
The remarkable thing about the findings, according to Wake, is the consistency. "Despite the fact that this evidence comes from a wide range of environments "“ the atmosphere, the biosphere, the oceans, and snow and ice "“ the remarkably consistent signal of a warming trend across the region cannot and should not be ignored. We now have our canary in the coal mine."
Markham agrees. "For those who are still asking for scientific evidence supporting the notion that we are already seeing the kinds of effects scientists have been warning us we'd see from global warming, here it is."
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