The Climate & Health Meeting was organized to replace the Centers for Disease Control and Prevention's climate change conference, which was postponed in January, ahead of President Donald Trump's inauguration. The Trump administration did not explicitly ask for the move, CNN reported in January.
The meeting became a subject of controversy as Trump prepared to take office last month.
However, the meeting allowed experts to sound alarms about the deadly health risks associated with climate change.
Between 2030 and 2050, climate change is projected to cause about 250,000 additional deaths per year from heat stress, malnutrition and the spread of infectious diseases like malaria, according to the World Health Organization
"The extreme weather events calculated by the insurance industry have obviously been increasing," former US Vice President Al Gore said in a keynote speech at the meeting. "As I've said on other occasions, every night on the television news now is like a nature hike through the Book of Revelation."
The majority of climate scientists
-- 97% -- agree that climate change is real and human pollution is largely responsible.
Some scientists question whether the WHO projection might be an underestimate, especially since approximating future death rates has proved to be difficult. Yet many agree that the number of climate-related deaths is expected to rise.
"Those WHO statistics are just from some very specific health outcomes where we have some known working equations and models to do it," said Dr. Jonathan Patz, a professor and director of the Global Health Institute at the University of Wisconsin-Madison, who participated in the meeting.
"Some of the questions about how many deaths will climate change cause, it may be unanswerable as far as a specific number, but when you look at the multiple pathways through which climate disrupts all sorts of health outcomes, it could be enormous," he said. "Those numbers from WHO, I think, were an example but a drop in the bucket as far as really what the impacts could be."
Heat waves and health
Of all climate-related causes of death, heat stress is responsible for the most deaths in the United States, Gore said. He hosted the event along with the American Public Health Association and more than 50 organizations representing scientists, policymakers and activists.
"Mortality increases 4% on average during these heat waves," he said.
Data from the US Natural Hazard Statistics
show that heat caused the most weather-related fatalities, on average, between both 1986 and 2015 and 2006 and 2015. However, flooding caused the most weather-related deaths in 2015 alone.
"Globally, flooding on a global basis has first place," Gore said.
An increase of thousands to tens of thousands of premature heat-related deaths in the summer is projected each year by the end of the century, according to a climate and health assessment released by the US Global Change Research Program
Last year was Earth's hottest year on record
since record-keeping began in the 1880s, according to the World Meteorological Organization
"There is a clear warming trend, and that threatens health. It threatens our health. The Earth is warming because of our concentrations of greenhouse gases. The rate of warming in the last 30 years outpaces anything in the prior 1,000 years," said Kim Knowlton, senior scientist at the Natural Resources Defense Council and assistant clinical professor at the Columbia University Mailman School of Public Health, during a panel discussion at Thursday's meeting.
"Heat waves, which are extreme heat events that last several days, are the No. 1 cause of US weather-related fatalities on average over the last 30 years, more than tornadoes, more than floods, more than lightning," she said.
More, different disease tracking needed
Along with heat, the spread of infectious diseases can pose a higher risk of death, and high temperatures can play a role in the spread of such diseases.
Climate change can impact human infectious disease via the pathogen itself, via the host or by creating conditions for transmission, according to a study published in the journal Environment International
last year. The study involved reviewing research on climate change and health published between 1990 and 2015.
For instance, warmer and wetter weather can provide ideal conditions for disease-carrying mosquitoes
to flourish, promoting the spread of mosquito-borne diseases.
This might have occurred recently in the spread of the Zika virus.
Although a combination of factors played a role in the Zika outbreak, changes in the environment caused by climate change can influence the spread of mosquitoes carrying the virus, according to a document from the CDC
"From November to January, there have been 5,000, or 4,000 or more, cases of Zika in Puerto Rico," Gore said during his keynote speech at the meeting.
"The CDC does an outstanding job, but there were budget constraints and political maneuvering, and no need to get into that here, except to make the point, we need better monitoring," he said. "We need the kind of disease surveillance that will help the public health experts prepare for this and mobilize their resources."
Gore also mentioned how many plants, especially crops, suffer from climate impacts.
More extreme weather events, from high temperatures to flooding, can prevent crops from growing and reduce yields, but higher CO2 levels could also affect the foods you eat.
"Essential nutrients like zinc, iron, copper, magnesium and calcium could decrease significantly in the food crops that we rely upon, and this is not because of higher temperatures; this is because of higher CO2 levels," Gore said in his speech.
Elevated CO2 has been associated with reduced protein and nitrogen content in alfalfa and soybean plants, resulting in a loss of quality, according to the US Environmental Protection Agency
A controversial meeting
Despite the controversy surrounding the meeting, Gore and other presenters seemed pleased with the turnout.
"They tried to cancel this conference but it is going forward anyway," Gore said in a statement January 26
"Today we face a challenging political climate, but climate shouldn't be a political issue. Health professionals urgently need the very best science in order to protect the public, and climate science has increasingly critical implications for their day-to-day work," he said in the statement. "With more and more hot days, which exacerbate the proliferation of the Zika virus and other public health threats, we cannot afford to waste any time."
The Carter Center
is a nonprofit founded by former President Jimmy Carter and his wife, Rosalynn Carter, to fight disease, hunger, poverty, conflict and oppression around the world. Carter offered use of its facilities for Thursday's Climate & Health Meeting.
In a guest appearance at the meeting, Carter said that while considering the possible opinion or disapproval of Congress, "the CDC has to be a little bit cautious politically; the Carter Center doesn't."
Experts hope efforts to reverse climate change effects also will benefit public health -- and death rate projections.
"It's very hard to quantify worldwide death rates from climate change. We can do it in relatively small ways, malaria, hunger, severe storms, but the really big killers are likely to be dropoffs in nutrition, infectious diseases that are a result of both spreading vectors and of poor nutrition, population dislocation and migration," said Dr. Howard Frumkin, a professor at the University of Washington School of Public Health, who participated in the meeting.
What will determine the projected number of deaths, he said, will be "depending on how good a job we do in dealing with climate change."