Extreme weather induced by climate change has dire public health consequences, as heat waves threaten the vulnerable, storm runoff overwhelms city sewage systems and hotter summer days bake more pollution into asthma-inducing smog, scientists say.

The United States – to say nothing of the developed world – is unprepared for such conditions predicted by myriad climate models and already being seen today, warn climate researchers and public health officials.

"Climate change as it's projected will impact almost every aspect of public health, both in the developed world and – more importantly – in the developing world," said Michael McGeehin, director of the Environmental Hazards and Health Effects division at the Centers for Disease Control and Prevention.

"A flood is a major public health disaster," he added. "A flood takes us back to the 1890s as far as the public health system is concerned."

Last week, as the East Coast stewed its way through the first heat wave of the summer, researchers at Stanford University published a study suggesting exceptionally long heat waves and extreme temperatures could be commonplace in the United States within 30 years – sooner than expected.

"I did not expect to see anything this large within the next three decades," Noah Diffenbaugh, assistant professor of environmental Earth system science at Stanford and lead author of the study, said in a statement. "It was definitely a surprise."

The report was published in the journal Geophysical Research Letters.

Using some of the highest-resolution computer models to date, Diffenbaugh and Moetasim Ashfaq, a former Stanford postdoctoral researcher now at Oak Ridge National Laboratory, were able to simulate daily temperatures across small sections of the country.

They found an intense heat wave – equal to the longest on record from 1951 to 1999 – could hit western and central United States as many as five times between 2020 and 2029.

The study buttresses other recent findings concluding that the heat scorching the eastern United States last week – or that killed tens of thousands in Europe in 2003 – is likely to be the new norm.

"The current state of heatwaves could be the harbinger of things to come," said David Easterling, a climatologist with the National Climatic Data Center.

And it's not just heat.

Easterling and McGeehin spoke at a briefing last week arranged by the Union of Concerned Scientists. Climate disruption, they said, is also bringing more floods and drought.

"A flood is a major public health disaster," McGeehin said. "A flood takes us back to the 1890s as far as the public health system is concerned."

There is, however, a silver lining: Tackling global warming is also a public health opportunity, said Jonathan Patz, director of global environmental health at the University of Wisconsin, Madison, who also participated in the UCS briefing.

Avoiding the worst of the heat waves, sewage overflows and droughts has obvious benefit, Patz said. But many climate mitigation efforts also bring health benefits: Using less fuel improves air quality; walking or biking to work reduces obesity.

Patz is in the process of quantifying those savings, but preliminary results suggest that if Americans could reduce their car travel by 20 percent – essentially not driving one day a week – the largest cities across the Midwest could save hundreds of lives, avoid hundreds of thousands of hospital admissions and trim several billion dollars from health care spending, he said.

"If you were to turn those trips into active transport – that is walking or biking – you could probably double those health care (savings)," he added.

This article originally appeared at The Daily Climate, the climate change news source published by Environmental Health Sciences, a nonprofit media company.