Frost coated the Chesapeake Bay region about 100 times a year in the early 1900s. A century later, there are about 30 fewer chilly mornings.
The number of balmy nights, during which temperatures don’t drop below 68 degrees, has grown by a similar margin. Plants spend a month less in winter hibernation than they once did.
Climate change is not an abstract concept about microscopic changes in carbon dioxide levels or subtle rises in sea level, scientists at the University of Maryland Center for Environmental Science say. It’s already evident in the Chesapeake.
The center’s researchers have gathered more than 100 years of data from continuously monitored sites around the bay to document what has been occurring so gradually that it’s mostly unnoticed by Chesapeake area residents.
The scientists analyzed trends in temperature and precipitation, looking at extremes and variability, to show the ways climate has changed, often imperceptibly, over generations. They found that the changes, as subtle as they may seem, have been significant. Rainfall, for example, has increased by more than 4 inches over a century, a gain of 12 percent.
Several papers outlining the findings are being reviewed for publication in scientific journals. The articles will explain the extent to which climate already has changed around the Chesapeake and how it could threaten bay ecology going forward.
But, perhaps more importantly, the researchers say, they want to share the data with the public to illustrate what can be a confusing and controversial topic. They have launched a website designed to better inform the casual bay advocate, added a chapter to a textbook on the ecology of the Chesapeake offered for use in middle and high school classrooms, and they are sharing their findings with other state and federal environmental agencies to disseminate the message.
They hope that presenting climate data on a local level “would make people who live around the bay feel ownership around the data and the processes we’re describing,” said Victoria Coles, a research assistant professor at the center’s Horn Point Laboratory in Cambridge, Md.
Coles and Raleigh Hood, a professor at Horn Point, have spent the past two years studying 114 years of data from around the bay.
The observations come from Eastern Shore, Southern Maryland and upper bay outposts of the National Estuarine Research Reserves, a division of the National Oceanic and Atmospheric Administration. Data also was collected at four such reserves along the York River in Virginia, and at 18 other stations from the Susquehanna River to the mouth of the Chesapeake.
They chose to focus on the weather trends that tend to stick in memories — periods of unusual warmth or wetness, for example — to help people compare their experiences with actual data. They said they hope this helps people better understand how climate is changing and how their actions contribute to those environmental shifts.
For example, residents might remember heavy rainfall events like the one that devastated downtown Ellicott City last summer. But they don’t know that such extreme weather has translated to a significant change in climate — an increase from about 39 inches of annual rainfall in 1920 to more than 45 inches in 2000.
The researchers have translated the complex and dense graphs of the changes into more simplified displays that show clear upward trends in precipitation levels and so-called “tropical nights” as well as a decline in frost days.
“Organisms and people feel weather; they don’t really feel climate,” Coles said.
Those graphs now appear on a website the researchers want to promote, at www.chesapeakedata.com/changingchesapeake.
And they will be highlighted in a new chapter of the Chesapeake Bay Ecosystem Atlas, an online textbook written by a Virginia consultant and used in middle and high school classrooms around the bay region.
The book traces the bay’s history, starting from a meteorite strike 35 million years ago, and details its complex food web, from microscopic plankton to rockfish. The researchers’ work is forming the basis of a fifth and final chapter that will show students the effects of climate change on the bay, said Dave Jasinski, vice president of Chesapeake Environmental Communications in Richmond, and the book’s author.
He said the data can help people realize that global warming isn’t hypothetical or far off.
“People always think of climate change as, ‘That’s something I’ll worry about tomorrow,’” Jasinski said. “It’s not an eventual thing. It’s a now thing. It’s an ‘already has happened’ thing.”
The researchers hope to disseminate their findings through the National Centers for Coastal Ocean Science, a part of NOAA that has a lab in Oxford on the Eastern Shore, and through other NOAA offices, including the estuarine research reserves. In Maryland, the reserves include the Anita C. Leight Estuary Center on Otter Point Creek in Abingdon, the Jug Bay Wetlands Sanctuary on the Patuxent River near Upper Marlboro, and a reserve on Monie Bay near Deal Island in Somerset County.
And the scientists plan to explain and continue studying the ways the climate changes they observed are affecting the bay.
Scientific papers they expect to release soon examine ways the warming trends could allow tick-borne diseases and harmful Vibrio bacteria to thrive or could hurt larval fish. Another paper scrutinizes precipitation changes to understand how much more often downpours are occurring and how extreme they are, perhaps better informing agricultural practices or urban management of storm water runoff.
James McGarry, Maryland and District of Columbia policy director for the Chesapeake Climate Action Network, was not surprised by the findings. He said the research provides helpful information as climate policy is being discussed in Washington.