Previously just the worry of climate scientists, environmentalists, doomsday prognosticators, and gas-price watchers, climate change is starting to worry some others— public health specialists, who say that global warming could affect large swaths of the population.

In a paper published in the journal PLoS Medicine Tuesday, a group of European public health experts write that climate change could alter "patterns of physical activity and food availability, and in some cases [bring] direct physical harm." Slight temperature increases could also change disease distribution in colder regions and make hotter regions less hospitable to humans.

"Certain subgroups are at more risk—mainly the young, the old, and the poor," says Peter Byass, director of the Umea Centre for Global Health Research in Sweden. "The middle age and wealthy will be better off. It's a crude way of looking at it, but it's not so far off the mark."

That means more prevalence of diseases that affect the poor, such as malaria and dengue fever, and heat stroke in drought-afflicted areas.

For years, scientists have warned about more extreme hurricanes and weather patterns, but until recently, not much emphasis was put on less noticeable changes.

"I don't think there's a big gang of global health experts saying [climate change] is unimportant," he says. "But I don't think people have been making the connections that need to be made between public health and climate change."

Byass' paper isn't the first time health officials have pondered the human toll of climate change. In March, a group of doctors suggested that the incidence of asthma and other lung respiratory illnesses could increase, due to longer pollen seasons and increasing ranges of disease-causing molds and mosquitoes.

"At this point, we might not be able to stop climate change, but we can be a bit prepared as to what the consequences might be," he says.

It's something people in his field are increasingly worried about. At last year's "Durban Climate Meeting," a United Nations convention to discuss climate change, people focused on health issues had their say. The unpredictability of climate change—there are many models of what might happen over the next century—makes Byass' and his colleagues' jobs much harder, he says.

"I think it's pretty clear that things won't stay the same, so we can talk about the what-ifs of different climate change [theories], but it's hard to say for sure what will happen," he says.

The United Nations has been placing more of an emphasis on climate change, with many of its member countries asking the world's largest carbon producers—China, India, and the United States—to enter legally-binding agreements to reduce emissions. This year, government officials will meet in Doha to continue negotiating.

Late last year, officials from around the world met in Durban, South Africa at what is now known as the "Durban Climate Meeting," in which officials from India, the United States, and China agreed to continue negotiating legally-binding carbon emission rules.

"It's about behaving in a way that's responsible for the planet. One would hope the United Nations could help get everyone together," Byass says. Countries must be willing to take an economic hit in becoming more energy efficient. "Protecting the future of the planet has a price tag, there's no doubt about that."

Jason Koebler is a science and technology reporter for U.S. News & World Report. You can follow him on Twitter or reach him at jkoebler@usnews.com.