Horn Point scientist talks climate change in Chesapeake Bay
ST. MICHAELS — University of Maryland’s Horn Point Laboratory offered a program called “Changing Chesapeake: What’s in store for the Eastern Shore” on Dec. 3 at the St. Michaels branch of the Talbot County Free Library.
The purpose of the lecture series is to have an educated citizenry on the Eastern Shore, according to Horn Point Director Mike Roman.
Climate scientist Dr. Victoria Coles led an interactive presentation to about 35 people, examining global climate change on a local basis.
Coles drew on research from her findings dating back two years. The study examined weather stations positioned close to the Chesapeake Bay. Data trends over the past century ultimately revealed fewer frost days, more heat events and more rain in big events.
While the scientist acknowledged that the audience may already be aware of such facts, the data confirmed evidence of global climate change on a local basis.
In the early 1900s, the percentage of days with daily highs below the 10th percentile — or top 10 percent of coldest days — numbered about 17, whereas now the statistic has dropped to just eight, according to Coles’ research.
Nighttime temperatures are warming faster than daytime temperatures, Coles said. At the start of the 20th century, the percentage of days with daily lows above the 90th percentile numbered nine, as opposed to about 13 days as of recent.
The scientist said the rainfall from heavy events is increasing; however, annual rainfall has remained the same. Therefore, local areas are experiencing a small increase of consecutive dry days.
One audience member questioned accuracy in the data, given its lengthy timeframe.
Coles said the numbers are supported by a total of 146 weather stations, 27 of which had data from 1900 to 1920.
“For precipitation, I’m not so sure that they’re excellent, but for temperature they’re not so bad,” she said.
Likewise, Coles said there is confidence in long-term projections, but not so much in the next decade.
The scientist also pointed out some aspects have not changed significantly.
“We don’t seem to be getting maximum changes in the absolute minimum temperature we observe over time,” she said. “We still are going to hit freezing conditions, and we will get snow all the way projected into the future.”
A major topic of discussion was growing season length, which is defined as the number of days that crops can grow and Coles said is specifically defined by wheat.
Since 1910, the length of the growing season has increased by more than 30 days, according to www. chesapeakedata.com/changingchesapeake.
With spring beginning earlier and winter starting later, Coles said farmers could potentially do double cropping, or two crops in every year.
Risks, however, can include crop losses in wet or freezing springs and excess nutrients from agriculture seeping into water bodies.
“Temperature increases actually hurt crop yield in some cases,” Coles said. “When there is an increase in temperature by one degree, farmers might be able to double crop but crop yields will lower as a result of the increasing temperatures.”
Coles said submerged aquatic vegetation like sea grasses experience heat stress when water temperatures are above 30 degrees Celsius for an extended period of time.
She asked the crowd to think about restoring grasses that are less heat sensitive, and therefore suggested against replanting Zostera.
In shallow areas of the Bay, there is a tight coupling between atmospheric temperatures and water temperatures, which breaks down at the freezing point, with a oneto- one correlation between the two, Coles said.
“Marshes are gaining sediment — some are losing elevation and sinking faster,” she said. “Sea level rise is overwhelming their ability to absorb sediment.”
The marsh ecosystem is central to removing nutrients before they enter the Bay, she said.
“We should make sure we don’t overbuild behind the marshes so they aren’t able to retreat up the landscape,” Coles said.
According to Coles, global sea rise is at about 3 millimeters per year.
“Science is suggesting that we need people in the community to be honest, trusted sources,” Coles said. “It takes people talking amongst themselves in the community to sort of open that discussion and get ... people thinking more about climate change. We have to go out and introduce those topics to them. And start responding.”
Horn Point Lab climate scientist Victoria Coles says the community needs to open discussion about climate change, and start responding to it.