You may have already begun noticing the subtle, less distinct turn of seasons in Pennsylvania and New Jersey, as evidenced in this fall's late — and less vibrant — leaf color changes.

That's only one of multiple visible signs that climate change is having, and will continue to have, an impact on the Northeast, according to the Fourth National Climate Assessment. Indeed, the report found the Northeast is among the areas most heavily impacted by rising temperatures and rising seas. From 1982 to 2013, the annual average sea surface temperature on the Northeast coastal shelf rose at a rate three times faster than the global rate.

The Trump administration released the assessment, which is mandated by Congress, over the Thanksgiving holiday weekend. Environmental groups claimed the timing was intended to bury the sweeping report. Manifestations of a changing climate detailed in the report include sea level rise along the coast, less snowpack for skiing, negative impacts on infrastructure, and more visits to emergency rooms due to heat increases.  For example, in the Northeast, we can expect approximately 650 more deaths per year caused by extreme heat by 2050, the report states.

The report also warns that after a soggy weekend and continued rain Monday, more deluges could be the big news of the future.

"The recent dominant trend in precipitation throughout the Northeast has been toward increases in rainfall intensity, with increases in intensity exceeding those in other regions of the contiguous United States," said a summary within the report. "Further increases in rainfall intensity are expected, with increases in total precipitation expected during the winter and spring but with little change in the summer."

The report pulled no punches at what's to blame: increasing levels of carbon dioxide produced by humans burning fossil fuels. In fact, very few of the assessment's findings are relatively new, though the level of detail of data indicating climate change is much greater.

"Scientists have understood the fundamental physics of climate change for almost 200 years," the authors, from 13 federal agencies, state. "In the 1850s, researchers demonstrated that carbon dioxide and other naturally occurring greenhouse gases in the atmosphere prevent some of the heat radiating from Earth's surface from escaping to space: This is known as the greenhouse effect."

The energy sector accounts for 84 percent of greenhouse gas emissions in the U.S., the authors state.

"Climate change is real, it's us, it's here now, and it's getting worse, but it's not too late to avoid the worst effects," said Robert Kopp, director of the Rutgers Institute of Earth, Ocean, and Atmospheric Sciences. He said, however, greenhouse gas emissions have to be reduced to avoid "substantial damage over the coming decades."

Meanwhile, President Trump told reporters Monday he did not believe the report's findings of eventual economic fallout from climate change, according to Politico. Trump said he had read parts of the report and "it's fine," but added that the U.S. is the "cleanest we've ever been" and laid blame on nations such as China for increasing greenhouse gas emissions.  A statement from the White House to the New York Times over the weekend said the report was "largely based on the most extreme scenario" of global warming, promising that "the next assessment would provide an opportunity for greater balance."

Among the report's findings for the Northeast:

Changing coastlines

Shorelines such as New Jersey's coast, as well as the Delaware Bay, support millions of people each year in tourism, sport fishing, aquaculture and recreation.  But the report says those industries are threatened by already observed, as well as projected, increases in temperature, storm frequency and intensity, sea levels, and ocean acidification.

Already, ocean warming is having an impact on where marine organisms and fish can reasonably live. Continued warming is expected to change the boundaries, and even lead to disputes, on commercial fishing areas.

Data show flooding is more frequent along the coastlines. Multiple communities along the Delaware Bay shore have already been dismantled, or are being dismantled, because of steady erosion and increased flooding attributed to more storms and sea-level rise.

Hotter, wetter cities

The Northeast is home to some of the largest urban areas of the country, including Philadelphia, New York, and Boston.

The cities are marked by paved surfaces, such as concrete and asphalt, which tend to lead to higher temperatures than in surrounding areas because of the heat island effect. In times of dangerous, major heat waves, temperatures at night in cities are generally several degrees higher than in surrounding suburbs and rural areas with comparative abundance in tree cover. In Philadelphia, there can be a 20-degree difference in temperature from one part of the city to another. Supporting the report's findings, the city is already trying to grapple with how to make hotter areas, marked by rowhouses and few trees, cooler.

With projected increases in both warmth and rainfall, urban areas are at risk not only of infrastructure damage, but potentially more emergency response efforts.  Recent data, separate from the climate assessment, show that the city's average temperature has risen 2 degrees Fahrenheit in the last 30 years. Temperature rise has a disproportionate impact on poorer and minority residents, given that the warmest neighborhoods also are the most economically stressed and are majority black or Hispanic.

In New Jersey, a statewide summary found a 3 degree Fahrenheit rise in annual temperatures since the beginning of the 20th century, a spike in the number of very hot days, warm nights and extreme precipitation events.

Observed number of very hot days in New Jersey.
NOAA
Observed number of very hot days in New Jersey.

The assessment notes that most cities will be under pressure to make costly changes to antiquated water drainage and sewer systems not designed to handle ever-heavier loads of precipitation from more big storm events. Now, many systems overflow during such storms events and that water ends up in rivers and streams. Locally, those streams and rivers ultimately drain in the Schuylkill and Delaware River, the city's source for drinking water.

Annual Precipitation Averages in Philadelphia

Five-year precipitation averages, in inches, compared with the average since 1900.
Staff Graphic

"Much of the infrastructure in the Northeast, including drainage and sewer systems, flood and storm protection assets, transportation systems, and power supply, is nearing the end of its planned life expectancy," the authors wrote.

Pennsylvania, for example, has experienced a large increase in heavy rain events, according to a statewide summary. It has seen a sharp spike in the number of warm nights and increases in tidal flooding.

NOAA

Shifting seasons

Data within the assessment show that climactic changes include warmer springs, longer summer dry seasons, and other impacts.

The authors note that the distinct seasonality of the Northeast has been one of its hallmarks and attractions, giving it a separate sense of place to many other regions of the U.S. But those seasons are becoming less distinct, they say, leading to milder winter and earlier spring conditions that alter ecosystems, agriculture and the environment, "in ways that adversely impact tourism, farming, and forestry."

The assessment includes maps showing further projected shifts in the date of the last spring freeze and the date of the first fall freeze by mid-century.  By that point, the freeze-free period across much of the Northeast is expected to lengthen by as much as two to three weeks.  By the end of the century, most of the Northeast will see the freeze-free period extended by three weeks over recent decades.

"The seasonal climate, natural systems, and accessibility of certain types of recreation are threatened by declining snow and ice, rising sea levels, and rising temperatures," the assessment states. "By 2035, and under both lower and higher scenarios, the Northeast is projected to be more than 3.6 degrees Fahrenheit warmer on average than during the preindustrial era. This would be the largest increase in the contiguous United States and would occur as much as two decades before global average temperatures reach a similar milestone."