Climate Changes Bring Increased And Intensified Rainfalls To NJ Two Released Studies Show

By: Follow South Jersey Staff

SOUTH JERSEY — Precipitation across New Jersey has increased over the last 20 years and is projected to increase in intensity through the end of this century due to climate change, according to two studies by the Northeast Regional Climate Center.

The studies by Dr. Arthur DeGaetano, director of the Northeast Regional Climate Center and professor of Earth and Atmospheric Sciences at Cornell University, and peer-reviewed by DEP’s Science Advisory Board, provide a range of rainfall projections dependent on the warming scenario. These reports, which fill in 20 years of climate data gaps, will aid governments, communities and businesses in their work to build greater climate resilience.

“While New Jersey is ground zero for some of the worst impacts of climate change, this science provides us another opportunity to ensure that our communities become more resilient,” NJ Environmental Protection (NJ DEP) Commissioner Shawn M. LaTourette said in a press release from the department.

“As we saw late this summer with the remnants of Tropical Storms Henri and Ida, more frequent and intense storms are our reality today, and we can expect these extreme precipitation events to continue, even worsen, in the years ahead,” LaTourette continued. “By building upon our scientific understanding, we can take the wise steps that the science demands: from planning more resilient development, to enhancing our stormwater and flood control infrastructure and beyond. We all have the power to ensure that what we build today will stand the test of time and a changing climate.”

The studies show:

  • Precipitation is already 2.5% to 10% higher. The precipitation expectations that presently guide state policy, planning and development criteria, and which rely upon data obtained through 1999, do not accurately reflect current precipitation intensity conditions. Extreme precipitation amounts are 2.5% higher now than the 1999 data suggests, and some parts of the state have seen a 10% increase above the outdated data. 
  • Precipitation is likely to increase by more than 20% from the 1999 baseline by 2100, and projected changes will be greater in the northern part of the state than in the southern and coastal areas, with projections for some northwestern counties seeing the greatest increase, some by as much as 50%. 

The first study, Changes in Hourly and Daily Extreme Rainfall Amounts in NJ since the Publication of NOAA Atlas 14 Volume, closes climate data gaps and addresses how measures of storm intensity change by incorporating the past two decades of data into the current analyses.

The study found that at more than half of the stations reviewed, extreme precipitation amounts are 2.5% higher now than those published in 2000. In some places, the additional 20 years of data reflects a more than 10% increase above the outdated data.

The second report, Projected Changes in Extreme Rainfall in New Jersey based on an Ensemble of Downscaled Climate Model Projections, addresses changes to precipitation intensity that can be expected by the middle and latter part of the century.

The data from this study indicate that there is a high likelihood that precipitation intensity will increase throughout the century in all parts of the state, but the projected changes will be greater in the northern part of the state than in the southern and coastal areas. The report provides mid and late-century projections for each county. Key findings:

  • Under a scenario of moderate increases in atmospheric warming of about 3.2˚F (1.8˚C), projections suggest that the amount of precipitation associated with the 100-year, 24-hour storm will increase by 20% to 25% in northern counties, on average.
  • For the 100-year, 24-hour storm, the models suggest that there is a 17% chance that precipitation associated with this type of storm will increase by as much as 45% to 50% in some counties.
  • More frequent storms, such as the 2-year and 10-year, 24-hour storms are expected to see increases in precipitation intensity of 5% to 15% on average across the state by the end of the century.

“As we move into a warmer and wetter world, it is crucial that the most recent rainfall observations and state-of-the-art climate model simulations of future rainfall be incorporated into decisions regarding flood potential, infrastructure design and resiliency planning,” DeGaetano said.

These two reports went through a peer review by the DEP Science Advisory Board’s standing committee for Climate and Atmospheric Sciences, led by Dr. Anthony Broccoli, Co-Director of the Rutgers Climate Institute and faculty member in the Department of Environmental Sciences.

“One of the consequences of climate change is that we can no longer assume that what has happened in the past is a guide to the future,” Broccoli said. “These studies will provide better guidance for estimating and managing future risks to human life, property, and infrastructure.”

Notably, the studies will provide  the scientific basis for the ongoing development and modification of rules to be introduced under the state’s NJPACT (Protecting Against Climate Threats) and NJREAL (Resilient Environments and Landscapes) initiatives as directed by Governor Murphy’s Executive Order 100.

Among other storm types studied, what is often referred to as the 100-year, 24-hour storm is included. A 100-year storm is one that has a 1 percent chance of occurring based on past historical records and represents the total amount of rainfall likely to fall within a 24-hour period.

Despite the name, it is a mistake to assume such a rainfall occurs once every 100 years, NJ DEP stated. It means that there is a 1 percent chance in any given year that this type of storm will hit any given area. In fact, the remnants of Tropical Storms Henri and Ida, though considered 100-year-storms, hit the same areas less than two week apart this past summer, the studies show.

The long-term projections were developed from a combination of 47 climate models under moderate and high future emissions scenarios. The modeled storms included those with a 50% chance of occurring each year (also known as a 2-year storm), a 20% chance of occurring each year (5-year storm), a 10% chance of occurring each year (10-year storm), a 4% chance of occurring each year (25-year storm), a 2% chance of occurring each year (50-year storm), and a 1% chance of occurring each year (100-year storm).

The studies and a research summary are available at

The Science Advisory and Board review and responses are available at

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