Dire warning: We’ll suffer more 90-degree days, climate report says

Double the number of scorching hot days and whipsaw bouts of overwhelming rain and debilitating drought could mar South Florida’s future if more efforts aren’t made to mitigate climate change, according to a federal study released this month.

The Climate Science Special Report, which is overseen by the U.S. Global Change Research Program, is produced every four years and is a far-reaching study of the potential impacts of a warming world.

While much of the report confirms dire forecasts already predicted, the candid blame placed on humans for climate change strongly validates most of the scientific community’s beliefs that the biggest contributor to rising temperatures is man.

Check The Palm Beach Post radar map.

Air temperature globally has increased by about 1.8 degrees over the past 115 years, making the period between 1901 to 2016 the warmest in the history of modern civilization, according to the report.

“It is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century,” the report says. “For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence.”

THANKSGIVING WEEKEND FORECAST: We’ll have a soggy Thanksgiving, then a nice punch of cool, dry air

For the most part, individual states are not parsed out in what amounts to a 2,000-page document, but there are pieces specific to Florida, including an estimated increase in days where temperatures reach higher than 90 degrees, more frequent extreme rainfall events, rising seas and the potential for more intense hurricanes with warming ocean temperatures.

Related: Florida suffers hottest first four months in 122 years.

Under a worse-case-scenario, South Florida could see up to 70 more days per year of temperatures warmer than 90 degrees by the mid-21st Century.

West Palm Beach, on average, already has about 65 days per year above 90 degrees, according to David Easterling, National Climate Assessment Technical Support Unit Director at NOAA’s National Centers for Environmental Information.

Easterling, who helped write a section of the report on temperature changes in the U.S., said the warmer days will also come with higher humidity.

“Combining the heat with the increase in humidity does raise a lot of concern by 2075,” Easterling said. “If apparent, or feels-like, temperatures are well into the 100s, there can be a lot of health affects.”

Rising temperatures can set off a chain reaction that overloads electrical capacity and cuts off South Florida’s air conditioning lifeline.

Look no further than September for an example of what happens when temperatures rise and electricity fails.

Related: Nation and Florida post second warmest years on record.

Hurricane Irma left millions of Floridians in the dark. Temperatures in South Florida fluctuated from the high 80s into the low 90s following the storm’s Sept. 10 landfall.

At the Rehabilitation Center at Hollywood Hills, which lost power to its central air conditioning system, 14 people died after living several days in temperatures not mitigated by central air conditioning.

“The biggest risk to human life in weather-related disasters are heat waves,” said Ben Kirtman, professor of atmospheric sciences at University of Miami’s Rosenstiel School of Marine and Atmospheric Studies. “If we have a hurricane and there is a week to ten days with no power, that means elderly people in high rises that can’t get out of the building. That’s when we start losing people.”

The heat analysis includes a jarring map of the U.S. painted in deep red hues to signify the increase of days with higher than 90-degree temperatures.

Florida Climatologist David Zierden said the map looks alarming, but is the worst possible outcome under the highest emission scenario. It also uses a comparison with the time period 1976-2005 — one of the coldest periods of the century in the southeast and Florida.

“It ignores the warmer decades of the 1930s through 1950s,” Zierden said.

Still, Easterling said with higher temperatures comes higher rainfall events because warm air holds more moisture. At the same time, warm air causes more evaporation, which, depending on the time of year, can mean higher incidences of drought.

“You could have a lot of heavy rainfall and then drought,” Easterling said. “You go from famine to feast to famine again.”

South Florida experienced this scenario also this year when extreme drought gripped enough of the region that the South Florida Water Management District issued a water shortage order in April. By the end of June, a glut of rain had wiped out the drought. By October, so much rain had fallen that swollen Lake Okeechobee was above 17-feet — a level that triggers daily inspections of the Herbert Hoover Dike.

“I’m afraid what we’re seeing now is a harbinger of the future,” said Leonard Berry, professor emeritus at Florida Atlantic University’s geosciences department. “We will see more intense downpours alongside the problem of longer drought periods.”

What the report doesn’t do, is give much of a roadmap for local officials to combat or live with the affects of climate change, said Kirtman.

While it is another “pile of evidence” that human activities are modifying the climate in the long term, Kirtman argues scientists need to deal with issues on a more local level.

“We need to rethink this problem and look at the next five, 10, 20 years, as opposed to projections to 2100,” he said. “These reports are helpful and solidify the science, but we have to make it relevant for the people making decisions now.”

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