WASHINGTON (AP) -
The combination of global warming and shifting population means that by
mid-century, there will be a huge increase in the number of Americans
sweating through days that are extremely hot, a new study says.
People are
migrating into areas - especially in the South - where the heat is likely to
increase more, said the authors of a study published by the journal Nature
Climate Change. The study highlighted the Houston-Dallas-San Antonio and
Atlanta-Charlotte-Raleigh corridors as the places where the double whammy
looks to be the biggest.
"It’s not just the
climate that is changing in the future,” said study co-author Linda Mearns,
a senior scientist at the National Center for Atmospheric Research in
Boulder, Colorado. “It is many things: how many people and where people are
that affects their exposure to climate changes.”
In a unique study
looking at the interplay of projected changes in climate and population,
scientists tried to characterize the number of people who will feel
temperatures of 95 degrees or higher and how often they will feel it. They
used a figure called person days for the extreme heat to reflect both the
length of time heat waves continued and how many people felt it by
multiplying people affected by how many days they felt the heat.
Between 1970 and
2000, the U.S. averaged about 2.3 billion person days of extreme heat each
year. But between 2040 and 2070 that number will be between 10 and 14
billion person days a year, according to the study.
The biggest
projected increases in person days is the Texas, Oklahoma, Louisiana,
Arkansas census region where by mid-century heat exposure will increase by
2.7 billion person days. Right behind is south Atlantic region of Florida,
Georgia, South Carolina, North Carolina, Virginia, West Virginia, Maryland,
Delaware and Washington, D.C., where heat exposure is projected to increase
by 2.2 billion person days. New England gets off the easiest with an
increase of only 71 million person days.
The scientists used
11 different climate models based on current trends of heat-trapping carbon
dioxide emissions and matched those with demographic trends. Both the
increased heat and population shifts had about equal effects but together
they made matters even worse, said lead author Bryan Jones, a population
geographer at the City University of New York.
The question is,
will people adapt by changing their lifestyle, such as staying indoors and
using more air conditioning, or will they move to cooler climates. Jones
said it is unlikely that people will move to cooler areas to escape the
heat, saying historically people tend to move away from colder areas and
into warmer areas like Florida, Arizona and North Carolina.
The scientists
chose a threshold of 95 degrees because “at 95 people really, really start
feeling it,” Mearns said. “Even in a dry climate and I’m sitting here in
Boulder, Colorado.”
Several outside
scientists praised the study. University of Georgia meteorology professor
Marshall Shepherd said the problem is likely even worse when you take into
consideration the fact that cities get hotter than rural areas.