Climate Point: More rain and flooding woes

Flooding, sewer overflows and fish kills this week were a reminder that extreme rainfall is one of the key ways climate change already multiplies the threats in natural weather disasters.

Welcome to Climate Point, your weekly guide to news about climate change, energy and the environment. I’m Dinah Voyles Pulver from USA TODAY’s national team.

For anyone who’s ever strolled through New Orleans in the heat of the night, or sauntered through Savannah, it’s easy to understand how warmer temperatures intensify the amount of humidity in the air. For every 1.8 degrees of warming, scientists tell us the air holds 7% more water vapor. They’ve seen clear trends in the Eastern U.S. as warmer temperatures and a warming Gulf of Mexico supercharge even routine rain storms.

The overabundance of rain that arrives in sudden events drew attention around the country this week.

Scientists along the Atlantic Coast grapple with the effects of rainfall and warming temperatures on good phytoplankton that are the building blocks of ocean food chains and dangerous plankton that cause fish kills and estuary collapses.

Over the past 50 years, the levels of phytoplankton ‒ important tiny plants that are the foundation of the marine food chain ‒ have declined by 50% in Rhode Island’s Narragansett Bay, reported Alex Kuffner in an in-depth piece in the Providence Journal. The decline is attributed to increased rainfall, rising temperatures and less mixing in the water column, all linked to climate change. Scientists are concerned about a ripple effect in the Bay's food chain and other far-reaching effects on the larger ecosystem, as well as impacts on the fishing industry.

Kuffner took to the waters of the Bay with researchers in New England’s largest estuary, viewing a bloom of diatoms, a microscopic plant eaten by oysters and quahogs as well as tiny animals called zooplankton that are consumed by crabs, shrimp and fish, going all the way up the chain to seals, dolphins and osprey. Through photosynthesis, phytoplankton produce half of the world’s oxygen and are responsible for as much as a quarter of all carbon absorption.

Researchers find the bloom is shifting in time, happening about five days earlier every decade, Kuffner writes. While it may be too early to determine the impact, the finding raises concerns of a phenological mismatch – that life cycles that have fallen into sync over thousands of years are having their timing thrown off by climate change.

In the Chesapeake Bay, a dangerous phytoplankton is being blamed for fish kills , reported Kristian Jaime with the Salisbury Daily Times. A research team led by Baltimore's University of Maryland Center for Environmental Science found the toxin Karlodinium Veneficum has proven deadly to fish, shellfish, small sharks and even laboratory mice.

Debby's intense rain leaves a wake of polluted water and flooding

In Southwest Florida: Warm temperatures in the Gulf of Mexico and adjacent coastal waters and an influx of stormwater from heavy rain in Tropical Storm Debby in Southwest Florida may be to blame for a fish kill in Matlacha Pass by lowering oxygen levels in the water.

Warmer temperatures increase microbial action, said Calusa Waterkeeper Emeritus John Cassani, in a story by Chad Gillis in the Fort Myers News Press. “They need oxygen and they’re competing for oxygen with fish and shellfish."

"With Debby, all that water runs past the water control structures and into Matlacha Pass, and that area is going to have a lot of nutrients and pollution," said Jim Beever, a retired biologist and climate change planner.

Savannah, Georgia: Debby was consistent with the trend scientists have documented in slower-moving and stalling tropical systems dropping increasingly intense rainfall, reported John Deem with the Savannah Morning News. Debby handed Savannah its wettest August in nearly three decades , Not since 1995, when more than 17 inches fell, has Savannah seen as much August rain as the 11.5 inches by mid-month according to the National Oceanic and Atmospheric Administration .

Deem's stories also point out the dichotomy in the changing climate. While extreme rainfall events are becoming more common , Savannah, like other communities in parts of the Southeast, is seeing longer dry periods as temperatures rise.

On the Jersey Shore: Heavy rain was blamed for a bacteria warning off six beaches on the Jersey Shore .

Tropical storms aren't the only events bringing heavier rain

Northeast flooding: Days after Debby caused flooding along the East Coast, a surprise deluge soaked a swath of the Northeast through New York and Connecticut, claiming two lives as the water rose quickly in streets and neighborhoods. More than 14.8 inches of rain fell in Oxford, Connecticut between Saturday night and Monday morning, the National Weather Service reported. Ten inches fell in Suffolk County, New York.

Milwaukee rain concerns: In Milwaukee, residents were asked to reduce their water use ahead of a heavy slug of rainfall that threatened to overflow the area’s combined sewer, which combines the flow of stormwater and wastewater from homes and businesses for treatment.

Iowa flooding: About 5,400 Iowa families got good news in their quest to recover from a bout of flooding in June. The families struck by flooding will receive about $56 million in federal housing aid, reported Donnelle Eller at the Des Moines Register. The Federal Emergency Management Agency aid will help repair homes and cover the cost of temporary places to live and other critical needs not covered by insurance.

Throwback: A December 2021 investigation by USA TODAY explained how the warmer climate is bringing more intense rainfall.

Talking climate change

In Chicago this week, the Climate Action Campaign and other climate groups met with leaders in town for the Democratic National Convention, to call for more action to address the disasters being made worse by the warming climate. “We’re here because as each day passes, climate-fueled extreme heat, floods, and fires become more severe, more damaging, more costly, and more deadly,” stated Rep. Kathy Castor, a Florida Democrat.

Already this year, the National Oceanic and Atmospheric Administration has tallied 19 billion-dollar weather disasters, and insured losses have been estimated at greater than $60 billion.

At the convention, the party platform approved by Democrats this week addressed climate change , reported Madeline Heim with the Milwaukee Journal Sentinel. The current platform of the Republican Party doesn't mention climate change, Heim reported earlier in the summer, but an increasing number of younger Republicans are pushing the party to elevate the issue .

Could hailstones grow even bigger?

A team of researchers led by scientists at Northern Illinois University found warmer temperatures in the future could lead to increases in the size of hailstones over two inches. That's because warmer temperatures at the surface are creating stronger updrafts in the most severe thunderstorms. Those updrafts can keep hailstones bouncing around inside a storm, where super cooled liquids attach themselves to hailstones, making them larger and larger.

Some scientists say we're already seeing an increase in severe convective storms and may be experiencing increases in hail size, but more research and time is needed for conclusive evidence. National record hail size reports from the weather service have grown progressively larger.

A hailstone in Minnesota in July measured 6 inches in diameter and was the largest reported in the state in at least 38 years. It could be a state overall record, but the historical data isn't enough to prove or disprove it, according to the state's Department of Natural Resources.

Read on for more, including electric cars, offshore wind and pursuing pesky pythons. Some of the stories below may require a subscription. Sign up to access eNewspapers in the USA TODAY Network. If someone forwarded you this email and you'd like to receive Climate Point in your inbox for free once a week, sign up here .

This article originally appeared on USA TODAY: Climate Point: More rain and flooding woes