Imagine you are on a bike descending a long, steep hill when your brakes fail. As you gather more speed, you face a life-extinguishing event at the bottom unless the brakes start working again. This is an apt analogy for the greatest challenge to human existence on our small planet. As the monumental and varied environmental effects of climate change become undeniably apparent, our brakes are beginning to fail.

Climate change is among the topics 2020 Democratic presidential hopefuls will address during future presidential debates. It should be. While the current administration’s efforts to leave the United Nations climate agreement have further politicized this issue, it is more than mere fodder for partisan politics. 

Simply put, climate change is an existential threat to our health and continued life on the planet. 

Climate change is insidious. It is an important contributor to devastating hurricanes, extreme heat, desertification, drenching rainstorms, and other life-threatening environmental changes. Yet it is not the sole cause, so it is easy for the remaining small band of climate change deniers to disavow its true impact. But the pattern of changes clearly confirms its effects are protean and increasing.

In the debate over its causes, we have obscured the simple truth that climate change has been damaging our health for years. It took an unprecedented coalition of public health groups to point this out. Earlier this year the American Medical Association, American Heart Association and 72 additional, respected health and medical organizations issued a collective call to action outlining 10 steps that need to be taken to avert public health disaster. The statement calls climate change, “one of the greatest threats to health America has ever faced — it is a true public health emergency.”

This push for commitments to fight the health impacts of climate change comes at a critical time. This summer, hundreds of wildfires have been burning in scores of communities across the Western U.S. causing respiratory and other health problems. Wildfires even broke out in the Arctic this summer. Climate change means more intense and frequent wildfires churning out waves of smoke scientists say will sweep across the continent to affect tens of millions of people and cause a spike in premature deaths.  

At the same time, record-setting heat waves hit nearly everywhere on the globe. Record-high temperatures gripped cities and towns across America, impacting approximately 200 million people and resulting in heat-related illness.

Triple-digit temperatures hit U.S. communities — especially those in Oklahoma, Kansas, Iowa, Missouri, Illinois and the East Coast, causing cities like New York, Los Angeles and Chicago to cancel events and set up cooling stations for those at risk. It’s too soon to tally death tolls from the heat wave, but by comparison, the less severe 2003 European heat wave killed 70,000 people, including 15,000 in France alone.

Those are only two climate-related health issues: We have dozens with which we must contend. Climate change makes existing health problems worse, but also creates new, unexpected health threats, according to the U.S. Government’s Global Change Research Program’s assessment of climate change’s impact on human health in the U.S.

Global impacts can take the form of heat-related illnesses (heat exhaustion, hyperthermia and heatstroke), respiratory and cardiac illness, allergies and asthma (which become more severe and can limit productivity); food- and water-borne diseases, starvation due to crop failures, vector-borne diseases (malaria, West Nile disease and others); extreme weather events (which increasingly cause fatal physical injury); and stress and other mental health consequences.

This array of health problems is prompting medical schools to change their curriculum to train doctors to cope with the growing impacts of climate change.

Beyond public health impacts, there’s the looming problem of healing the planet. Journalist David Wallace-Wells, author of “The Uninhabitable Earth” is not alone in estimating that humans have only three decades in which to stave off climate disaster. His projections are supported by the UN Intergovernmental Panel on Climate Change, which last year called for coal-fired electricity to end by 2050 if we are to limit global warming rises to 1.5C (2.5 degrees Fahrenheit). If not, they warn that we may see a major climate crisis in just 20 years. 

The clock is ticking as the impacts of climate change mount quickly, reaching into every aspect of health and life. Countering this dire set of circumstances is a daunting prospect, but the call to action put forward by the 74 health and medical organization presents two clear paths.  

First, we must adapt our public health plans to meet what is surely coming. We must increase climate resilience to the certain increases in pollution, temperatures, extreme weather and sea level rise. This requires not only public, medical provider and public health education and preparedness but also anticipatory actions in agriculture, the built environment, public works and water conservation. Since the greatest near-term concern is on human health, public health agencies at all levels of government should be taking the lead in coordinating and planning to adapt to the inevitable. 

Second, our nation must be an active participant in slowing, stopping and reversing CO2 and methane release into the atmosphere. We must meet and strengthen the commitments the U.S. made under the Paris Climate Agreement, impressing on lawmakers, businesses and the White House that it is a matter of public health and safety in the short term and our continued existence on the planet in the longer term. 

We must re-establish a leadership position among nations that includes transitioning rapidly away from the use of coal, oil and natural gas to renewable and efficient energy systems; moving to zero-carbon transportation systems; promoting healthy, sustainable and resilient farms and food systems, forests, and natural lands; ensuring all U.S. residents have access to safe, sustainable drinking water supplies; and investing in policies that support a just transition for workers and communities adversely impacted by climate change or the transition to low-carbon economies.

A recent U.N. report finds that up to one million of the estimated eight million plant and animal species on Earth are at risk of extinction from climate change. Humans can’t escape this trend. The health and safety of millions in the U.S. are being affected now. Whether or not our grandchildren have a future depends on what we do next. Planning to meet the health impacts of climate change is a good first step. But preventing the “disease” in the first place — doing all that we can to reduce greenhouse gas emissions and pollutants — is employing the precautionary principle. In this case, it is the only sane approach.

Jonathan Fielding, M.D., is a professor of public health and pediatrics at University of California, Los Angeles.