Climate change impacts Delaware River basin, including near Philadelphia

The average annual air temperature in the Delaware River Basin has risen 3 degrees in about a century — one of several indicators scientists said this week paint a “big picture of dramatic and accelerating climate change.”

The scientists met with government leaders at the annual conference of the non-profit Partnership for the Delaware Estuary (PDE) to share their findings that warming has increased four times as fast over the past 30 years as it did in the period from 1910 to 2021.

“Temperatures are rising pretty fast,” said Raymond Najjar, an oceanographer at Penn State, in a keynote address at the Atlantic City conference, which was attended by about 250 people. As he spoke, January was nearing its end with nearly 10 degrees above normal.

Najjar also spoke about the impact of climate change on Philadelphia, the largest city on the estuary or tidal portion of the Delaware River. In Philadelphia alone, sea levels are rising at a rate that suggests an extra foot by the end of the century.

Najjar cited data from the US Historical Climatology Network (USHCN) database compiled from 15 weather stations distributed across the basin. The acceleration in air temperature, he said, “really stood out” as the rise over the past three decades has been as rapid as the rise over 300 years ago.

Najjar, along with Jill Arriola, an assistant professor in the Department of Meteorology and Atmospheric Sciences at Penn State, co-authored the climate chapter in the Estuary and Basin Partnership’s 2022 Comprehensive Technical Report, which is updated every five years.

The report finds trends within the vast area of ​​land and waterways in New York, Pennsylvania, New Jersey and Delaware that empties into the 330-mile-long Delaware River. The non-tidal upper river runs 200 miles from the headwaters in New York to Trenton; The lower tide runs from Trenton through Philadelphia and Wilmington before emptying into the Atlantic Ocean.

Climate change, combined with development and pollution, can have dramatic effects on the basin, the report said. It can alter water chemistry, worsen harmful algal blooms, reduce water clarity, increase salinity and cause more flooding. The river is a source of drinking water for 13 million people.

Overall, the report rates the river basin’s health as “fair” given positive trends such as cleaner water, rehabilitation projects, removal of dams and increases in wildlife such as osprey, blue crab and sturgeons.

warmer air

Modeling suggests that some parts of the basin would be 12.6 degrees warmer by the end of the century compared to the 1986-2015 period if greenhouse gas emissions continue to rise, the PDE report notes. But even if the gases recede, temperatures would still rise 7.2 degrees.

“This accelerated warming is probably the clearest and most dramatic indicator that the climate of the Delaware Estuary and Basin is changing rapidly,” the report said.

Warmer temperatures in the basin are likely to make people living in some Philadelphia neighborhoods increasingly uncomfortable, Najjar said, as they grapple with an increasingly muggy heat island effect — related to areas with a high concentration of buildings and streets that absorb the sun’s heat absorb and release more than leafy areas.

“This shows how social justice issues interact with climate change very clearly,” Najjar said. “Those affected by climate change are the most vulnerable.”

Rising sea level

Sea level rise is not only affecting the Atlantic coast, but also the Delaware tidal area.

In Philadelphia, sea levels have risen at an average rate of 3.1 millimeters (0.12 inches) per year for the past 120 years. But that has accelerated to about 4.7 millimeters (0.18 inches) over the past 30 years — a rate that suggests an additional foot of sea level rise by the end of the century.

A low-lying stretch of Camden surrounded by waterways, including the river, is already struggling to stem further flooding officials believe is being caused in part by climate change.

» READ MORE: ‘Every time it rains’: Flooding due to climate change plagues a neighborhood in Camden

Sea levels have risen about 7 inches at the mouth of Delaware Bay over the past 30 years, increasing the amount of salt in the water. By 2100, sea level rise at the low end of projections is projected to increase by 20 inches to as much as 5 feet compared to 2020 average levels. The effect is amplified because the surrounding land is sinking due to its geology.

Overall, the report says, sea-level rise contributes to property damage, loss of beaches and dunes; pushes in saltwater that kills forests and causes public safety problems during floods.

Though data suggests sea temperatures could be rising, scientists say more monitoring and analysis is needed. And although precipitation is increasing, particularly in the upper basin, the overall trend is also not clear.

However, the report expects the trend toward less snow to continue and “represents not only a change in the character of winter in the Delaware Estuary and Basin, but also a concern for water resource managers and local economies that rely on winter recreation.” should give. ”

As the conference wrapped up Wednesday, Philly ended a 325-day snow-free streak with 0.3 inches of fast-melting snow.