Accountant Michael Scott, his wife and their two kids have been living in their first home since 1999, but recently became concerned that it's in a high-risk flood zone in a low-lying area along the east side of the San Francisco Bay.

The area has never flooded due to natural causes, Scott said, but his worry stems from scientific global warming predictions that his San Leandro, CA, home, just 75 feet from Estudillo Creek, could be inundated within 50 years -- if not sooner -- along with dozens of other homes in coastal communities nationwide.

To ease his concerns he's rationalized that by the time global warming creates a worst-case scenario, if it does, his kids will be grown, the house paid off and he'll have plenty of time to flee to higher ground before rising sea levels force him out.

"We decided we like the community here and there's always a chance that the predictions are wrong or that they will send up a red flag and people will take action. It doesn't seem like anything is going to happen for at least 10 years or more," he says.

He hopes.

But what if Scott had to shop for a home today?

"If we were looking for a home, would we move here now? No. Probably not," he concedes.

Global warming is beginning to impact the choices some people make about where to buy a home.

Chances are, only a tiny fraction of home buyers like Scott actually give a toastier planet a second thought when they consider a home purchase.

But low-lying areas and arid, drought-prone regions and others which are likely to first feel the effects of global warming are certainly putting new meaning into the phrase, "Location. Location. Location."

"Everybody is not going to pick up and move today, but with 15 to 20 percent of the population moving every year, there are a growing number of people beginning to ask this question," said John McIlwain, an Urban Land Institute senior resident fellow who holds the institute's J. Ronald Terwilliger Chair for Housing.

"People aren't going to sit there and ask, 'Should I move?', but when they have decided to move they will think about where they should move," said McIlwain.

Impact of Global Warming

Global warming refers to a recent pattern of accelerated increases in Earth temperatures that are disrupting meteorological patterns and planetary conditions that sustain human life.

Nonbelievers abound, but most climate scientists, including those with National Aeronautics Space Administration (NASA); the National Academy of Sciences (NAS); and the World Meteorological Organization all say the planet is nearing a state of emergency and humans are helping push that state to a reality.

Carbon dioxide from burning fossil fuels adds to the heat trapped in the atmosphere, the so-called "greenhouse effect," and that's expanding desert regions, raising temperatures, melting glaciers and ice caps and swelling sea levels at rates more perceptible and measurable than ever.

Scientists say the Earth has the highest levels of carbon dioxide in more than 400,000 years and the 10 hottest years on record since measurements were first recorded 125 years ago all have occurred since 1990.

In addition to burning fossil fuels, another global warming contributing factor is the "heat island" created by replacing natural cooling vegetation with large new home and commercial developments and with paved open space, according to the U.S. Environmental Protection Agency. The urban and suburban heat islands can produce temperatures 2 to 10 degrees hotter than nearby rural areas and aggravate smog, which worsens in hot weather, the EPA says.

Arthur H. Rosenfeld, a member of the California Energy Commission, says temperatures in the Los Angeles area have increased 7 degrees since 1940.

Some major cities, including Chicago, New York and Boston have taken to landscaping the rooftops of buildings to help offset the effect, but they could be too late.

How Hot Is It?

This year, ironically, just before a heat wave swept the nation, killing people in record numbers, the United Nations Environment Programme (UNEP) examining climate change in the desert, produced "Global Deserts Outlook". The report says the deserts of the world are getting hotter and the heat is spreading the desert and its ecosystem beyond existing desert borders.

Call it desert sprawl.

That trend and other climatic changes are beginning to negate predictable temperate weather patterns that generate demand and added property value. As excessive heat and increased smog become intolerable for some home buyers, the reduced demand could be a telling market factor.

"I grew up in Orange County. I've been there for 47 years and we used to have predictable weather patterns -- 85 in the summer and chilly in the winter and it was constant. A few weeks ago it was 115 degrees (F) in Diamond Bar," said celebrity appraiser Randall Bell of Anderson & Sanders LLC of Laguna Beach, CA.

Bell's work is the economic impact of detrimental conditions, such as environmental issues, floods, earthquakes and tornadoes as well as construction defects, soil problems, market cycles and more, including crimes and other stigmas associated with properties. Bell developed the noted "Bell Chart" a matrix of 10 categories, including "Natural Conditions" and their impact on the value of property.

His expertise makes him the Appraisal Institute's designated expert on the impact of global warming on housing values.

"The weather has become a wild card. Good weather is no longer guaranteed. I don't know if its measurable (in terms of an impact on values). There have been no formal studies. My only take on it is there is no place you can move in the U.S. with the assumption of good weather," Bell said.

When it comes to global warming weather, some low-lying coastal regions have already begun to feel the effects, according to scientists who this year said more hurricanes and more intense hurricanes in 2005 were a direct result of global warming.

A home's location right now can mean greater insurance costs, and higher insurance costs already make or break deals. Lenders won't sign off at closing if the homeowner can't obtain adequate coverage. Homes are less attractive as an investment if they come with prohibitively high insurance costs, limited coverage or coverage of last resort.