Darfur

Until the rains failed in Darfur, the region's pastoralists lived amicably with the settled farmers. The nomadic herders grazed their camels on the rocky hillsides between the fertile plots and fed their animals on the leavings from the harvest. But with the land crippled by a decades-long drought, the region was no longer able to support both. Farmers began to fence off their fields, and clashes broke out between sedentary and nomadic tribes. When a rebellion broke out in 2003, it began as a reaction to the Sudanese government's neglect. But although the rebels initially sought a pan-ethnic front against a distant, uncaring regime, the schism between those who opposed the government and those who supported it soon broke along ethnic lines. The camel-herding Arabs--those most envious of the farmers' lands--became Khartoum's staunchest stalwarts.

So what caused the rains to fail? When climate scientists studied the drought, they discovered that rising temperatures in the tropical and southern oceans had combined with cooling in the North Atlantic to disrupt the African monsoons. The roots of the drying in Darfur lay in changes to the global climate.

The crisis has since spilled over into Chad and the Central African Republic. Nomads from Sudan are pushing deep into the Congolese rainforest. Other regions are worried they will be next. When the United Nations Security Council held its first-ever debate on the impact of climate change last year, the Ghanaian representative stood up to declare that he hoped the "repeated alarm" about the threats posed by global warming would "lead to action that is timely, concerted and sustainable." In his country, climate change had expanded the Sahara desert, forcing the country's nomadic cattle herdsmen into agricultural lands. The pastoralists, he said, were buying high-powered assault rifles to defend their animals against angry local farmers.

The Gulf Coast

Climate scientists may still be debating to what extent climate change is going to translate into stronger and more frequent hurricanes, but insurance companies aren't waiting for the final answer. The 2004 and 2005 hurricane seasons, which included Hurricane Katrina and multiple landfalls in Florida, sent the industry reeling. More than 5.6 million claims paid out $81 billion.

Swiss Re, an insurer to insurance companies, keeps three climatologists on staff to try to predict such future damages. In a report released just before the 2004 season, the reinsurer predicted that another decade of global warming would cost insurers more than $30 billion in weather-related claims every year. With Katrina, the industry was facing that from one hurricane alone. "The whole underpinning of what insurance is about is that the past is an accurate predictor of the future," says Chris Walker, North American director of the Climate Group, a coalition of businesses and government that lobbies for action on global warming. "And if it's notbecause climate has changedthen you're in trouble&. If climate change changes the data that you're relying on as an insurer, then how do you price? How do you model? And if you don't price and model, are you only gambling?"

From the Texas docklands to the beaches of Cape Cod, coverage has become much harder to find, and much more expensivea reflection, says Robert Muir-Wood, chief research officer at Risk Management Solutions, Inc., a leading modeling firm, of the increased risk. Devastating hurricanes are potential symptoms of a disruption sweeping the entire world. "It's not that climate change is out there in the future," he says. "It's already happening. And the future will probably look a bit like this."

Italy

In August 2007, an epidemic swept through Castiglione di Cervia, a small village in northern Italy. More than 100 of the town's 2,000 residents came down with high fever, rashes and crushing pain in their bones and joints. An unusually mild winter had allowed Asian tiger mosquitoes to start breeding early, and their population had soared. When an Italian tourist returned from India with chikungunya, a relative of dengue fever, the insects provided the perfect vector. According to officials at the World Health Organization (WHO), the epidemic was the first European outbreak of a tropical disease caused by climate change.

Climate change has accelerated the spread of dengue fever and other tropical maladies, such as malaria, borne by mosquitoes. The insect's larvae mature more rapidly when the water in which they grow is warm. And female mosquitoes digest blood faster and bite more frequently as the mercury rises.

A malaria mosquito only lives a few weeks. The parasite's survival depends on it reaching maturity while its host is still alive to bite. In temperatures of 68 degrees Fahrenheit (20 degrees Celsius) the Plasmodium falciparum parasite takes 26 days to complete its reproductive cycle. At 77 degrees F (25 degrees C), it's ready to reinfect after just 13 days. "We're seeing changes in the range of mosquitoes and the diseases they carry," says Paul Epstein, associate director of Harvard Medical School's Center for Health and the Global Environment. "That's going to be an issue increasingly in terms of latitude and on the margins, both in terms of extensions of the range and in terms of seasonality."

Northern Europe

The warming of the globe has so far generally been good for the world's wine. It has allowed the fruit to come off the vine richer and riper. A study led by Gregory Jones, a climatologist at Southern Oregon University in Ashland, Ore., and the son of a winegrower, tracked the impact of rising temperatures between 1950 and 1999, using as a measure of quality the values by the auction house Sotheby's, which rates wines on a 100-point scale.

In the 27 wine regions Jones examined, temperatures had risen on average 2.3 degrees F (1.3 degrees C), producing a corresponding increase in the strength of the wines; faster ripening resulted in more sugar for the yeast to ferment. Even more striking was the warming's impact on ratings. With very few exceptions, they rose dramatically. On average, a 1.8-degree F (1-degree C) rise in temperature yielded a boost of 13 rating points. The big winners were German wines, with leaps of more than 20 points, and those from the cooler regions of France.

Yet after a series of unusual growing seasons, it's clear the future won't be so rosy. A 2003 European heat wave spurred growers into the earliest harvest on record and left a lot of wine tasting of raisins. By comparing a region's annual ratings with its yearly weather, Jones has been able to pinpoint the optimum temperature for an area's grapes. In the 1990s, according to Jones, climate change had warmed most regions to the point where quality was at or near its peak. As temperatures continue to rise, growers around the globe will begin to find that their fruit is ripening too fast. The best conditions for growing wine will spread north and uphill. Indeed, producers are already expanding into Holland, Belgium and even Denmark. In Spain they're moving into the Pyrenees. England probably has more land under wine cultivation than it did during its last heydaythe 12th century at the end of the Medieval Warm Period.

Great Barrier Reef

Not all the carbon dioxide we emit contributes to atmospheric warming. More than a third of what we have produced since the industrial revolution has been absorbed by the oceans, where it reacts with seawater to form carbonic acid. So far, we've added enough carbon to shift the pH of the world's waters from 8.2 to 8.1.

The first to feel the impact are the creatures of the sea that use calcium carbonate to form their shells and exoskeletons. The acidic (or actually less alkaline) water wears away at crabs, mollusks and sea snails. Coral reefs face a double whammy as the changing ocean chemistry adds to the stress of unusually warm water. Australia's Great Barrier Reef lost an estimated 10 percent of its coral to mass bleaching in 1998 and 2002. Overstressed colonies expelled the symbiotic algae that give them their color, leaving them bone white and weakened. The U.N. Intergovernmental Panel on Climate Change (IPCC) estimates that by 2050, 97 percent of the Great Barrier Reef will be bleaching yearly. Whereas the coral sometimes recovers, reabsorbing the algae, more often bleaching is the first step toward death.

The oceanic kaleidoscope may be among the first victims of the changing waters, but the devastation can be expected to work its way up the food chain. In Australia the seabird population has begun to drop steeply. The seafood industry could be next. As the reefs vanish, the fish will surely follow.

Island nations

Last summer, the tiny Pacific island nation of Kiribati became the first country to declare that global warming is rendering its lands uninhabitable, asking for help in evacuating its population. The IPCC estimates that melting land ice and thermal expansion will raise the levels of the seas by one to three feet (up to a meter) before the end of the century. Such a rise would be enough to put large portions of the country's 33 coral atolls under the level of the waves. Saltwater intrusion into the water table would leave many with nothing to drink.

While Kiribati awaits word if any countries will open their doors for its 100,000 residents, the Maldives--similarly threatened, but richer in tourist dollars--is shopping for a new homeland. In November, the country's first democratically elected president announced he was establishing an investment fund in hopes of buying new land for the country's 300,000 citizens. "We do not want to leave the Maldives," he told the Guardian, "but we also do not want to be climate refugees living in tents for decades." Although Sri Lanka and India are said to be preferred for their similar cultures and climates, Australia, with its vast, unoccupied lands, is another possibility.

Island nations aren't the only ones watching the waves. A three-foot rise in sea level would flood one seventh of Bangladesh's territory, force the Netherlands to beef up its flood control, and threaten coastal cities around the world. And even before the top tourist destinations disappear underwater, they will have lost their luster: Higher and wilder waves mean increased erosion, fewer white, sandy beaches, and more rocky coves.

Washington, D.C.

According to the Red Cross, environmental disasters displace more people than war. The London-based Christian Aid estimates that by 2050, floods, droughts and famine caused by climate change will have driven 250 million people from their homes--more than the 163 million people currently displaced by wars, famine or ecological disasters. Nearly all of these climate refugees will come from the world's poorest countries, where governments and citizens lack the resources to adapt to the perils of a warming world. "There's no question that, in many parts of the world, climate change--rises in sea level, desertification, deforestation--are having an impact on migration flows," says Brunson McKinley, director general of the International Organization for Migration in Geneva.

In richer countries the impact will more likely be political. Increased population flows are giving anti-immigrant groups an opportunity to couch their arguments in the language of the environment. The Sierra Club has undergone repeated takeover attempts by a close-the-borders wing, which has tried to add immigration reduction into the environmental group's purview. The Center for Immigration Studies in Washington, D.C., argues that people moving into the U.S. from the developing world are impeding the fight against climate change by producing four times as much carbon dioxide in their new homes as they would have in their native countries. "Already, a large volume of south to north migration in the Americas is straining some states and is the subject of national debate," 11 retired U.S. admirals and generals wrote in a 2007 report for the Center for Naval Analyses, a national security think tank. "The migration is now largely driven by economics and political instability," the report says. "The rate of immigration from Mexico to the United States is likely to rise because the water situation in Mexico is already marginal and could worsen with less rainfall and more droughts. Increases in weather disasters, such as hurricanes elsewhere, will also stimulate migrations to the United States."

The Northwest Passage

The melting of the Arctic has spurred a geopolitical race, as Russia, Norway, the U.S., Canada and Denmark press competing claims for the top of the world. But whereas the competition is in part driven by the promises of undiscovered metal, minerals and petroleum, the melting ice is already uncovering another valuable resource: the waves underneath it.

Ships that take the Northwest Passage from Europe to Asia could cut more than 4,000 miles (6,400 kilometers) off the trip through the Panama Canal. They won't have to go through locks, and ships of all sizes will be able to pass through. In September 2007, the European Space Agency announced that for the first time in recorded history the passage was fully navigable--at least for a brief period.

As the ice continues to melt, the shortcut will become increasingly viable. The multiyear sea ice of the Arctic ice cap is thick and resilient. As much as 26 feet (8 meters) thick and leached of salt, it can be as hard as concrete. In contrast, first-year ice is soft and pliable. Never more than 6.5 feet (1.82 meters) thick, it's much more easily broken by icebreakers or drill ships. "When you say you have a seasonally ice-free Arctic what that really means is you no longer have multiyear sea ice," says David Barber, a professor of environment, earth and resources at the University of Manitoba in Winnipeg and one of the world's leading experts on sea ice. "It means shipping throughout the year will be very possible." Recreational craft have already started to try their luck. And in November, a commercial cargo ship made the first successful crossing--delivering supplies from Montreal to communities in western Nunavut.

The Alps

According to the Organization for Economic Co-operation and Development, the Alps have been warming at roughly three times the global average, and projections show more to come. Alpine glaciers are in retreat, and mountain plants are migrating upward in pursuit of cooler temperatures. As the snow line creeps up the slopes, the winter sports industry, which attracts 60 to 80 million tourists a year, is threatened.

Ski resorts are starting to reinvent themselves in preparation of more seasons without the white stuff. Some destinations are coping by using man-made snow, hauling in powder from nearby glaciers or using helicopters for high-altitude runs. One Swiss village sold its ski operations for less than $1 in exchange for the promise that the new owner would build two new lifts to higher, snowier slopes.

Other mountaintop attractions are shutting their doors or doing what they can to transform themselves into year-round (ice-free) attractions. Towns that once specialized in getting skiers on the slopes are hoping spas, conference centers and luxury hotels will entice tourists and businesspeople to rise above the fray and make their getaways to high-elevation venues. In the Austrian Alps, the four-star Aqua Dome boasts a series of outdoor martini-shaped swimming pools, including saltwater soaks and a waterfall connected by two canals to the 140-room hotel. If there's a silver lining to the impact of climate change for Alpine tourism, it may be this: In a future of sizzling summers, the mountains, even ones mostly shorn of snow, may turn out to be a welcome retreat from the heat.

Uganda

In some places, efforts to address global warming are having a bigger impact than the changing climate itself. In the Mount Elgon National Park in eastern Uganda, a Dutch nonprofit group was reforesting the park's perimeter, earning carbon credits for airline passengers looking to make up for their emissions, and reinvesting the revenues to plant more trees. It was a project meant to benefit everyone. The trees were pulling carbon dioxide from the atmosphere, travelers were feeling less guilty, and Uganda was getting a bigger park. Yet that calculation didn't take into account the most vulnerable: the communities that once farmed the hills. Angry that their fields had been taken, they fought their expulsion with lawsuits and macheteseventually clearing many of the trees meant to capture carbon.

In the mountaintop conflict the farmers prevailed, but more often than not the poor lose out. In Ecuador community leaders near a similar project say that tree planting has cost them money. Efforts at carbon capture in Brazil and India have also resulted in conflict with next-door neighbors. The major challenges in the climate change negotiations for the treaty to replace the Kyoto Protocol will be the inclusion of forestry in greenhouse gas calculations and the resolution of disputes between rich and poor countries over who bears the greatest responsibility to cut carbon emissions. In both cases, the very poor risk being caught in the middle.