ROME When Dr. Giancarlo Icardi, health director for the Italian city of Genoa, got a call this summer that his young nephew was ill with a fever, headache and watery eyes after a day at the beach, global warming was not the first diagnosis on his mind. He suspected an out-of-season flu.
But 128 other beachgoers turned up at Genoa hospitals with similar symptoms that July weekend, forcing the closure of area beaches in the midst of a heat wave. Even though the health problems cleared up within a day, scientists quickly announced disturbing news about the culprit: a toxic warm-water alga that now grows in an increasingly warm Mediterranean Sea and had not previously bloomed in an Italian resort so far north.
"This is the first time that we've had this problem in Liguria," Icardi said, referring to the northern Italian region that includes Genoa. But scientists "discovered what it was quickly," he said, because in recent years disease-causing algae had cropped up at beaches in the Italian regions of Tuscany and Puglia, and in Spain.
As countries across Europe reduce production of greenhouse gases in order to fight climate change, scientists and citizens are discovering that effects of warming are already upon us. Irreversible warming is already happening, they say, and will continue for a century even if polluting emissions are controlled by the Kyoto Protocol, the international treaty aimed at limiting greenhouse gases.
To this end, they say, government and citizens must prepare for a steamier future, adapting to a climate that is hotter and stormier.
"In addition to mitigating climate warming, we should also be focusing on how to adapt," said Richard Klein of the Potsdam Institute for Climate Impact Research, in Germany. "In the last few years people have realized that climate change will happen. Adapting is not a choice - it's something we need to do."
The early warning signs of global warming are apparent: an increase in summer deaths due to heat waves in Europe; the northern migration of toxic algae and tropical fish to the Mediterranean; the spread of disease-carrying ticks into previously inhospitable parts of Sweden and the Czech Republic.
Scientists say that global warming may be partially responsible for the rising number of powerful hurricanes, like Katrina, as well as an increase in floods, like the ones that inundated parts of central Europe this summer.
Global warming also has been linked to recurring summer fires in Portugal, since the Iberian Peninsula has become hotter and dryer than in the past.
The role of global warming in creating any particular flood or fire or outbreak of disease is difficult to prove, since year-to-year temperature variability and other factors are involved. But the average number of yearly weather- and climate-related disasters in the 1990s was twice that of the 1980s, according to the European Environment Agency, in Copenhagen.
In response to this trend, countries and politicians are starting to think about changes they will have to make. French farmers are shifting to crops that better tolerate warmer temperatures - from corn to rapeseed, for example.
Austrian ski resorts that can no longer count on snow are planning hiking trails and golf courses.
The Italian city of Brescia is supplying the elderly with air-conditioners, a rarity in that country. Planners of the new Copenhagen subway raised all structures to allow for a half-meter, or 1.5-foot, rise in sea level that they expect global warming to cause in the next 100 years.
Most scientific models predict that, even with reduced emission standards promulgated by the Kyoto Protocol, temperatures will rise from 2 degrees to 6 degrees Celsius (4 degrees to 11 degrees Fahrenheit) in Europe over the next century - slightly less elsewhere in the world. And people are largely unprepared.
"Our resilience is quite low in the face of climate change," said Jacqueline McGlade, executive director of the European Environment Agency, which has published a report, "Impacts of Europe's Changing Climate," that catalogues areas of vulnerability and suggests how Europe can adapt.
She predicted that if nothing were done, people in northern and southern Europe, where the effect is expected to be greatest, would become "climate refugees," moving to the center of the continent.
"In the Arctic countries and southern Europe," McGlade said, "it will become harder and harder to sustain current living and consumption patterns."
Evidence of warming is now irrefutable, and almost all scientists believe it has been produced - or at least vastly accelerated - by emissions associated with industrialization.
The 1990s was the warmest decade in history. The years 1998, 2002 and 2003 were the hottest ever. By 2080, according to the Hadley Center for Climate Prediction and Research, in Britain, every second summer will be as hot or hotter than the scorching summer of 2003, when Europe recorded 20,000 excess deaths.
Southern Europe is likely to heat up earlier, within the next two decades, the European Environment Agency predicts. Cold winters, which occurred once every 10 years over the last three decades, are expected almost to disappear, McGlade said.
Already, scientists have been able to detect some hard evidence of climate change. "Until 10 years ago, we were mostly dealing with predictions and scenarios," said Roberto Bertollini, director of the Special Program on Health and Environment at the World Health Organization's European office. "Now, unfortunately, in the last few years, we are able to see and measure actual effects."
Some of the best-studied examples have been in Sweden, where scientists have documented the spread of disease-carrying ticks in tandem with warming weather. The insects - which carry Lyme disease and tick-borne encephalitis, a brain infection - need warm, short winters in order to survive.
"Variations in climate have had a very noticeable impact," said Elisabeth Lindgren of the University of Stockholm's department of systems ecology. "We're seeing disease in areas where we've never had it before, as well as more cases in areas where it previously existed."
In the 1990s, people in northern Sweden were told they were not vulnerable to these diseases, and took few precautions when venturing into the woods. Now, at the beginning of each spring, the Swedish authorities distribute maps showing ever widening areas of vulnerability.
Due to warmer winter temperatures, lakes in Sweden have more bacteria and detritus, affecting recreation and also the water supply, said Gesa Weyhenmeyer of the Swedish University of Agricultural Sciences in Uppsala.
Although Sweden made a big push to clean up Lake Malaren, just outside of Stockholm, in the 1960s and '70s, climate change has "counteracted our lake management effect," said Weyhenmeyer, adding: "Authorities monitor the water, but you can seldom swim there anymore because of harmful algae and bacteria." The Italian authorities are contemplating a similar program for Italy's Mediterranean beaches.
With winter temperatures in Sweden rising by up to 3 degrees Celsius in the 1990s, many parts of the country have lost their winter snow and ice cover in the last two decades, producing dramatic effects on ecology.
Because the land around Lake Malaren is no longer frozen during the winter, small brown particles of dirt leach into the lake, sometimes turning Stockholm's drinking water an unsightly shade of brown.
"Everyone wants to solve the problem, but it's hard to find a solution," Weyhenmeyer said.
Sometimes adapting to climate change is simple: The Swedish government is encouraging foresters to plant new species of trees that grow better in a slightly warmer climate, for example. In Hamburg and Rotterdam, new docks are being built to accommodate the likelihood of rising sea levels.
In other cases, adaptation would be so expensive that the authorities may opt to let nature take its course. Along the British coast in Norfolk and Essex, local governments are contemplating letting marginal coastal farmland, already beset by frequent flooding, simply sink into the sea as the water level rises.
"The most sensible thing may be for man to withdraw and change the coastline," Klein said.
"You won't have to pay subsidies. And these fields could probably become a healthy salt marsh, rather than poor farmland."