HERE’S a riddle: What do the Oklahoma dust bowl, smoke in Wenatchee, mold on Long Island and Washington’s oyster industry have in common?

And why would a doctor, like me, care?

The common link is climate change. We must act now to stop it.

Ken Burns’s PBS documentary, “The Dust Bowl,” recounts how reckless land management, combined with severe heat waves and drought during the 1930s, triggered a catastrophe — loss of soil, destruction of farms, displacement of people.

Record-breaking wildfires dominated the news last summer. Vast tracts of forest and grassland in central Washington and across the west were destroyed. People breathed higher levels of smoke than on the most polluted days in Beijing or Mexico City.

“Rockaway cough,” not to mention rashes, asthma, injuries and carbon-monoxide poisoning, are filling the emergency departments and relief centers of Long Island and New Jersey, as the victims of Superstorm Sandy endure numerous hazardous exposures in their efforts to clean up and rebuild.

And young oysters throughout the Pacific Northwest, confronted by more acid seawater, have been struggling to survive. Thousands of shellfish-industry jobs are threatened.

The Dust Bowl foreshadowed what’s now the new normal: droughts, heat waves, severe storms, floods, wild fires — exactly what experts predicted would occur with advancing climate change. But chaotic weather isn’t the only impact of climate change. Ocean acidification is threatening marine ecosystems, from coral reefs to oyster hatcheries. Rising sea levels threaten coastal cities and amplify the impacts of storms.

The other common link is human suffering. Climate change hurts real people, right now — respiratory diseases, injuries, depression, displacement, upended lives. Globally, the impacts include spreading infectious diseases, hunger aggravated by agricultural declines, wars over scarce resources.

In public health, when faced with threats to entire populations, we act. For infectious diseases, we vaccinate. For lung cancer, we ban smoking. For injuries, we install seat belts and air bags. For obesity, we promote physical activity and healthier eating.

For climate change, we need to act.

Here in Washington, we have many opportunities to protect health by addressing climate change:

• We need energy sources that don’t release greenhouse gases. The largest greenhouse emitter in the west is the Colstrip coal-burning power plant in Montana, and Colstrip’s largest owner is our own Puget Sound Energy. PSE should retire this plant.

• We need to help move the world past coal. Proposals to ship vast amounts of coal from the Powder River Basin through Washington or Oregon, and then to China, are dreadful health policy. That coal should stay in the ground — the only proven approach to “clean coal.”

• We need transportation policies that reduce greenhouse-gas emissions — more walking and cycling, more transit, less driving, more efficient vehicles. The expansion of our light-rail and streetcar systems, and our bike lanes, are sensible health policy.

• We need more energy-efficient buildings. Buildings account for more than 40 percent of global energy use. Seattle’s Priority Green, which expedites permitting for green buildings, promotes health directly and indirectly.

• We need to anticipate the effects of climate change, and prepare for them, to protect the public. Seattle’s Green Ribbon Commission recommends a strong approach to climate change “adaptation.” Those recommendations represent public-health preparedness, and we need to implement them.

When weather becomes chaotic and extreme, when ocean chemistry changes, when sea levels rise, people suffer. Fortunately, we have many options for protecting people for years to come. We need to act.

Howard Frumkin, a physician and epidemiologist, is dean of the University of Washington School of Public Health, and served on Seattle’s Green Ribbon Commission. The opinions expressed are his own.