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Climate change is set to become the "defining narrative of human health," a top medical journal warned Wednesday - triggering food shortages, deadly disasters and disease outbreaks that would dwarf the toll of the coronavirus. But aggressive efforts to curb greenhouse gas emissions from human activities could avert millions of unnecessary deaths, according to the analysis from more than 100 doctors and health experts.
In its annual "Countdown on health and climate change," the Lancet provides a sobering assessment of the dangers posed by a warming planet. More than a dozen measures of humanity's exposure to health-threatening weather extremes have climbed since last year's report.
"Humanity faces a crucial turning point," the doctors say, with nations poised to spend trillions of dollars on economic recovery from the pandemic and world leaders set to meet in Glasgow for a major U.N. climate conference in less than two weeks. The United States is working to assemble a set of climate policies to help coax bigger commitments from other top emitters at that conference, even as the Biden administration is scaling back its climate legislation, given opposition from Sen. Joe Manchin III, D-W.Va., who represents a coal-producing state.
Rising temperatures have led to higher rates of heat illness, causing farmworkers to collapse in fields and elderly people to die in their apartments. Insects carrying tropical diseases have multiplied and spread toward the poles. The amount of plant pollen in the air is increasing, worsening asthma and other respiratory conditions. Extreme floods and catastrophic storms have boosted the risk of cholera and other waterborne diseases. Smoke from fires in California infiltrates the lungs and then the bloodstreams of people as far away as Texas, Ohio and New York. Droughts intensify, crops fail, hunger stalks millions of the world's most vulnerable people.
"If nothing else will drive the message home about the present threat that climate change poses to our global society, this should," said Lachlan McIver, a Doctors Without Borders physician who was not involved in writing the Lancet report. "Your health, my health, the health of our parents and our children are at stake."
The Lancet study is just the latest salvo from health professionals demanding a swift end to burning fossil fuels and other planet-warming activities. In a special report released last week, the World Health Organization called climate change "the single biggest health threat facing humanity," warning that its effects could be more catastrophic and enduring than the coronavirus pandemic. Dozens of public health experts are headed to the U.N. climate summit starting at the end of the month, aiming to convince world leaders that they must take bolder action to curb their nations' carbon output.
Yet just half of countries surveyed said they have a national climate and health strategy in place, the Lancet study said. Trends in renewable energy generation and adaptation initiatives have improved only slightly. And most of the world's biggest emitters, including the United States, continue to subsidize fossil fuels at rates of tens of billions of dollars per year - rivaling the amounts they spend on public health.
The outcomes of national spending debates and international climate negotiations will either "lock humanity into an increasingly extreme and unpredictable environment," the report says, or "deliver a future of improved health, reduced inequity, and economic and environmental sustainability."
"Lowering greenhouse gas emissions is a prescription," said Renee Salas, an emergency medicine physician at Massachusetts General Hospital who helped write the "Countdown" and an accompanying policy brief aimed at U.S. lawmakers. "The oath I took as a doctor is to protect the health of my patients. Demanding action on climate change is how I can do that."
The world has not committed yet to cutting emissions enough to avert the worst effects of warming. Based on countries' current pledges under the Paris climate accord, average temperatures are on track to increase by a catastrophic 2.7 degrees Celsius (4.9 degrees Fahrenheit) by the end of the century. The planet has already warmed about 1.2 degrees Celsius (2.2 degrees Fahrenheit) since the preindustrial era.
And a U.N. report released Wednesday found that governments are still planning to boost fossil fuel use on a scale far beyond even those insufficient targets. G-20 countries have directed more new funding to fossil fuels than clean energy since the start of the pandemic, the report says.
The United States is one of the worst offenders, slated to increase oil and gas production by a combined nine exajoules by 2030 - the equivalent of about 215 million tons of oil - despite President Joe Biden's pledge to more than halve emissions by the end of the decade.
"A carbon-intensive COVID-19 recovery would irreversibly prevent the world from meeting climate commitments," the Lancet report warns.
The report draws repeated parallels between the coronavirus pandemic and the health crisis posed by climate change. Both have exposed and exacerbated inequality, and highlight the folly of prioritizing short-term economic interests over long-term consequences.
Yet the death toll from climate change will outstrip that of the coronavirus, the scientists warned - unless drastic action is taken to avert further warming and adapt to changes underway.
Already, climate change routinely threatens to overwhelm health systems' capacity to respond. When record-high temperatures scorched the Pacific Northwest this summer, the rate of emergency room admissions spiked to 69 times higher than the same period in 2019.
David Markel, an emergency physician at Swedish Medical Center's Cherry Hill campus in Seattle, said at the time that the surge of patients rivaled the worst days of the pandemic. He and his colleagues were treating patients in hallways, stuffing ice packs into people's armpits to bring their temperatures down.
"This is going to impact us all," Markel said. "The more crises like this we face, the more clear it is."
Just 0.3% of global climate change adaptation funding has been directed at health systems, the Lancet report says, despite an explosion of evidence for the health consequences of unchecked emissions. In the past month, studies in academic journals have reported the following:
El Niño weather patterns - which are projected to intensify as the planet warms - cause about 6 million children to go hungry.
Air pollution causes tens of thousands of early deaths among Americans each year, even at low levels deemed safe by the Environmental Protection Agency.
The warming of the Amazon, combined with deforestation, will expose roughly 11 million people to potentially lethal heat by the end of the century.
This drumbeat of new studies has been accentuated by a crescendo of recent climate-linked disasters: Drought in Madagascar has pushed more than 1 million people to the brink of starvation. Flash floods in Niger worsened the West African nation's cholera epidemic.
According to National Oceanic and Atmospheric Administration data, at least 538 Americans have died in major climate disasters this year. That doesn't account for the less-direct deaths: people who get sick from mold that forms after their home is deluged during a hurricane and patients whose chronic conditions are exacerbated by extreme temperatures. Studies suggest that smoke from wildfires led to thousands more coronavirus cases out West, and in one county was linked to 41% of deaths.
Recent disasters "are grim warnings that for every day that we delay our response to climate change, the situation gets more critical," said Marina Romanello, research director and lead author for the "Countdown."
Yet climate change's greatest dangers are not always associated with the most obvious weather extremes. Other threats will emerge from relatively slow, subtle transformations of the Earth and air.
By far the deadliest hazard comes from the act of burning fossil fuels, which generates tiny, lung-irritating particles known as PM2.5. One estimate published this February put the toll of this pollution at more than 10 million excess deaths each year. The Lancet study is more conservative, putting the figure closer to 1 million.
When it comes to the consequences of warming, heat is the world's worst killer. Elderly people and infants younger than 1 - the groups most vulnerable to heat - are exposed to roughly four more extremely hot days per year now than a generation ago, the Lancet report found. Almost 350,000 people died of heat-related illness in 2019.
Steadily rising temperatures, combined with habitat disruption and globalization, have also given infectious diseases a chance to evolve and expand.
Fungal illnesses, which can't be treated with vaccines or antibiotics, may be on the rise. Historically, there haven't been many fungi capable of infecting humans, because the microbes don't thrive at typical body temperatures. But as global warming increases the average temperatures in the environments where fungi live, it may be pressuring these species to adapt. This in turn could make them better suited for invading human guts or respiratory tracts, scientists suggest.
An April study in the journal PLOS Pathogens noted that Candida auris, a treatment-resistant infection that was first identified only 12 years ago, may have evolved this way. Same goes for a new kind of Cryptococcus gattii, a lung-infecting fungi typically found in the tropics, that recently emerged in the Pacific Northwest. In the Southwest United States, scientists have documented a rise in Valley Fever cases, which are caused by a fungus whose spores are spread on dusty, windy days that are now common because of climate-induced drought.
"They are kind of lurking in the soil and lurking in the environment," said Anita Sil, a microbial geneticist at the University of California at San Francisco who studies disease-causing fungi. "They're in the air we breathe."
Meanwhile, disease-carrying mosquitoes are moving to more temperate areas and higher elevations, their life cycles accelerated and their biting behaviors intensified. Shifting environmental factors have raised the basic reproductive rates of illnesses like Zika and chikungunya, enhancing their potential to explode into epidemics. A study published by the Lancet Planetary Health this July found that unabated carbon emissions would put almost 90% of the world's population at risk of malaria and dengue by the end of the century.
In the past decade, the Centers for Disease Control and Prevention has identified at least 128 cases in which people contracted dengue within the mainland United States. One case emerged as far north as New York.
But the diseases will continue to hit hardest in the low-lying, tropical nations where they are already endemic. In sub-Saharan Africa, McIver said, the toll could amount to as many as 50 additional deaths every hour, most of them in children under 5.
Other studies suggest that the rate of diarrheal diseases in children will increase as much as 5% for every 1 degree Celsius (1.8 degrees Fahrenheit) of temperature rise.
The particular danger to young children underscores what McIver calls the "cruel irony" of climate-related health threats: "Those who are being the most affected by the problem are those contributing least to the phenomenon of climate change," he said. "That's the thing we should all be staying awake at night thinking about."
On Capitol Hill and in international negotiations, the high price tag of addressing these impacts and moving the world away from fossil fuels has been an obstacle to climate legislation.
The Lancet "Countdown" argues that inaction will be even more expensive.
Last year, the direct costs of climate disasters totaled more than $178 billion, the report says. Drought affected 19% of the world's total land surface area, damaging yields of crucial crops such as wheat, corn and soy. Extreme heat harmed workers and shut down operations at farms and factories, depriving the world of 295 billion potential work hours.
But curbing emissions, investing in clean energy and funding adaptation efforts could save money as well as lives, the report says. The reduced air pollution that would result from eliminating fossil fuels alone could deliver global health benefits in the trillions of dollars. A 2019 study in the Proceedings of the National Academy of Sciences found that deaths from fine-particle pollution cost the United States more than $800 billion per year; more than half of those costs were attributable to pollution from the energy and transportation sectors.
"We have an enormous opportunity to get to the root cause of health harms from the burning of fossil fuels," Salas said. "To me there is no greater treatment that will have the widest health benefits for my patients than reducing greenhouse gas emissions."