The latest edition of a report on predicted climate change impacts, released by the Trump administration on Friday, says Maryland is already seeing some effects of rising global temperatures.
Many of them are well documented: more coastal floods, heavier downpours and shorter winters. Others are less well known, such as the disappearance of marshes, reduced air quality from wildfire smoke and more frequent waterborne illnesses.
The National Climate Assessment is required to be conducted every four years. Here is what the fourth such assessment predicts for Maryland:
Scientists expect that by 2040, the last spring freeze will arrive two or three weeks earlier than it does now, and the first fall freeze will come two or three weeks later than now. That would extend the growing season for plants and crops by a month or more. By 2070, they predict the season could be two months longer than it is now.
They say that could lead plants to lose their tolerance for cold temperatures, making them more vulnerable to being killed in years when the latest spring freeze comes earlier than usual. Early budding of flowering plants followed by hard freeze has already caused widespread losses of fruit crops and damaged native trees, the report says.
Less harsh winters will likely encourage insects to emerge earlier and expand their reaches across the country. That could include pests such as the hemlock woolly adelgid and emerald ash borer, insects that threaten hemlock and ash trees.
They could also increase populations of white-tailed deer and of nutria, an invasive rodent that eats away at Chesapeake Bay marshes. The study cites State Farm Insurance data showing deer-related vehicle crashes increasing in West Virginia and Pennsylvania.
Several decades of data show that through 2009, sea levels along the mid-Atlantic and Northeast coasts rose three to four times higher than the global average rate, according to the study. Scientists project waters to rise by between 2 feet and 4.5 feet by 2100 — or by more than 11 feet under worst-case scenarios.
The encroachment of salt water into and beyond marshes has already created what are known as “ghost forests,” in which salt water kills trees, in Maryland as well as southern New Jersey. It could be an increasing problem in the coming decades, the report says.
The report predicts potentially widespread marsh loss under worst-case scenarios of sea level rise. Even at lower rates of sea level rise, “marsh health will depend heavily upon site-specific hydrologic, physical, and sediment supply conditions,” the report says.
Some marsh loss will also increase because of erosion caused by feeding nutria. Marshes are considered key buffers to protect against other adverse impacts from climate change, including flooding and storm surge.
Rainfall intensity has increased more across the mid-Atlantic and Northeast more dramatically than other parts of the contiguous United States, the report says. “Further increases in rainfall intensity are expected, with increases in precipitation expected during the winter and spring with little change in the summer," the report says.
Strong hurricanes are expected to become more frequent and to drop more precipitation. In the event of a Category 4 storm, the surge would be expected to be so high it would wash over more than 80 percent of beaches along the coast, the report says.
High-tide flooding has already increased by a factor of 10 or more in recent decades in many coastal communities, such as Annapolis, and that trend is forecast to accelerate in the coming years. Property losses from hurricanes and other coastal storms is meanwhile expected to increase by billions of dollars by 2100.
Average temperatures are forecast to rise by 2.5 degrees over the next few decades, regardless of any changes in greenhouse gas emissions, the report says. And in the mid-Atlantic and Northeast, average temperatures could rise by 4 or 5 degrees by 2050.
That would mean several more days of extreme heat each year, and “substantially more premature deaths, hospital admissions, and emergency department visits” related to heat. Hundreds more people are expected to die across the Northeast because of the conditions.
The heat could also cause more power outages.
Poor air quality
Scientists predict more deaths related to ground-level ozone pollution, which is at its worst on hot, sunny days. Air quality has already suffered in Baltimore, at times, because of wildfire smoke blowing in from the west, and that is also expected to worsen air quality going forward.
Increased cases of illness related to campylobacteriosis and salmonella have already been documented in Maryland because of heavy rain washing contamination into streams and rivers. The report says increased precipitation could make sewage overflows more common — though in Baltimore, work to repair and replace sewer infrastructure could counter that trend.