Scripps Howard News Service, May 5, 2004
Just thinking of wintertime in Northern Michigan can make some people shiver, but the region's days as one of the nation's premier iceboxes may be numbered.
Warmer temperatures, less snow and less lake ice in recent decades have made Michigan's winter tourism industry one of the early victims of a changing climate.
Ski-resort operators say the average length of the winter season has shrunk one to two weeks. "We're fortunate we can make snow," said Jim MacInnes, president of the Crystal Mountain ski resort near Cadillac. "Whether this is just an anomaly or a long-term trend it's hard for me to know, but I do believe global warming is a real issue."
Michigan is not alone. Rather than a distant theoretical possibility, most scientists agree that global warming in the United States is a here-and-now reality. From the drought-parched Rocky Mountains to Florida's beaches to the hardwood forests of New England, early signs of climate change are virtually everywhere.
Evidence that the impact of global warming is already being felt "is becoming overwhelming," said John Magnuson, a professor emeritus at the University of Wisconsin who authored a landmark study of lake ice. It found a 150-year warming trend throughout the Northern Hemisphere. "I think we're just beginning to recognize that it's happening everywhere and the effects are different in the different regions of the country and different parts of the world."
While regional trends vary, in general temperatures are warmer. Rising temperatures mean greater evaporation. More water in the atmosphere means more frequent or more severe rainfall. Government-funded studies show that rainfall is increasing in much of the country _ as much as 40 percent in some places _ while some parts of the country are getting drier.
"We see an increase in overall precipitation of 5 to 10 percent over the past century, but the increase is especially prominent since the 1970s," said Tom Karl, director of the National Climatic Data Center in Ashville, N.C.
"But then if you look more closely at how precipitation is coming about, what we're seeing is that the increase is coming primarily through an increase in frequency and intensity of heavy and very heavy precipitation events," Karl said.
The increase in severe storms has been particularly dramatic in farm states _ Iowa, Missouri, Illinois, Nebraska, South Dakota and Wisconsin _ raising the potential for increased soil erosion and storm-water runoff from cropland.
"You hear a lot of stories from farmers and others that there has been a lot more damage _ 'This storm washed out my gullies' or 'This storm broke my terraces,' " said Craig Cox, executive director of the Soil and Water Conservation Society.
There has also been a marked increase in Atlantic hurricanes since the mid-1990s. From 1944 and 1996, there were an average of 9.8 hurricanes or tropical storms a year. But between 1995 and 2002, the average was 13.3. Last year, there were 16 named storms.
Some of the most dramatic effects have been on northern lakes. Water levels in Lake Michigan and Lake Huron, for example, started dropping in 1997 and have experienced their greatest decline in the shortest time since record-keeping began in 1860. Greater evaporation is believed to be the primary cause.
Lake Michigan levels are now 4 feet below normal and shipping has been severely hindered. Marinas have had to dredge to keep boats afloat and nuclear-power plants have had to extend their pipes to reach water for cooling.
In New England, Lake Champlain freezes over an average of eight days later in the winter than it did a century ago. Between 1815 and 1950, the lake failed to freeze over completely only six times; since 1950 it has failed to freeze more than 25 times.
Snowfall levels are declining, too. Over the past 50 years, the mean annual snowfall in Keene, N.H., has dropped by 23 inches, while Berlin, N.H., has seen a drop of 17 inches. The Arnold Arboretum in Boston is grappling with a die-off of hemlock trees due to an insect, the woolly adelgid, that is now able to survive the region's winters.
"I'm 61 years old and the winters of my high school years in the 1950s were fundamentally different than winters are now," said Barrett Rock, a research scientist at the University of New Hampshire who grew up in Vermont. "You used to get temperatures of 20 to 30 degrees below zero for days at a stretch. You just don't get those really hard cold snaps anymore."
New England's maple-sugar industry is one of the early casualties. Thanks to warmer winters, maple trees are ready for tapping two weeks to a month earlier than normal. With maple sugar, timing is everything _ tap a week too soon or a week too late and you can miss the best sap.
"Who knows, if the climate keeps changing maybe we'll be growing oranges up here in the future," said Alvin Clark, 72, whose family has been making maple sugar in Acworth, N.H., since 1893.
"These are the kinds of things we were projecting 10 years ago and now they are coming to pass," said Cynthia Rosenzweig, head of the Goddard Institute for Space Studies' Climate Impacts Group. "For scientists who have been involved in these issues for a long time it's really quite amazing."
In the New York metropolitan area, temperatures are warming faster than the global average, both droughts and severe storms have become more frequent and wetlands are being lost to rising sea levels, Rosenzweig said.
Local officials are working with scientists at Goddard and Columbia University's Earth Institute to figure out what changes need to be made to the region's roads, bridges, tunnels, subways, sewers, reservoirs, water-treatment plants, airports and power plants to withstand even greater climate impacts in the future.
Rising sea levels and flooding from more severe storms are a key concern. All three of the region's major airports -- Kennedy, LaGuardia and Newark -- are built on low marshlands. Much of lower Manhattan, including Battery Park, Wall Street and the World Trade Center site, are vulnerable to increased flooding.
The Holland Tunnel, with an annual traffic volume of 33 million vehicles, was built in 1927 to withstand a once-in-a-century storm surge of 6 feet. Current construction projects are required to be able to withstand a 9.8-foot surge and scientists say surges of 11 to 14 feet are possible in the future.
Like canaries in the mine, some species of wildlife are harbingers of environmental change. California's desert bighorn sheep, for example, are disappearing. A recent study published in Conservation Biology showed that 30 out of the 80 cluster populations that roamed the lower elevations of California mountain ranges over the last century are now extinct. Hotter, drier conditions resulting in less water and forage are probably to blame.
At the Archie Carr National Wildlife Refuge on the east coast of Florida, home to the largest loggerhead-turtle nesting area in the Western Hemisphere, the nesting season is peaking 10 days a year earlier than it did just 14 years ago, according to a study by University of Central Florida biology professor John Weishampel.
Data from a government buoy off Cape Canaveral show the sea surface temperature in May _ the month when the turtles start to come ashore _ has increased 1.5 degrees over the same period.
In Miami-Dade County, Fla., a governmental task force is working on recommendations for mitigating the potential impacts of global warming. "Our drinking water comes from subterranean aquifers so any sea level rise at all presents the threat of saltwater intrusion into our supply of freshwater," said Harvey Ruvin, a member of the task force.
"Should we start planning now for desalinization plants? Should we consider moving wells further west? There are a range of engineering options," Ruvin said.
The task force is also looking at whether more money should be budgeted to fight wildfires in the Everglades, combat the spread of tropical diseases and prevent beach erosion. But there is a limit to how much communities can adapt to climate change, Ruvin said.
"There are going to be engineering actions that may mitigate the damage, but the damage itself is going to have serious consequences," Ruvin said. "If (global warming) is unabated, Florida is going to end up as an island somewhere around Jacksonville where there is some high ground."