Birkel, Mayewski prepare report to help Mainers plan for climate challenges

Mainers can expect significant environmental changes in the next two decades due to increased greenhouse gas emissions and patterns of variability in the climate system, say University of Maine researchers Sean Birkel and Paul Mayewski.

And they’ve produced a report — Coastal Maine Climate Futures — to provide a base for coastal Maine planners to prepare for a variety of plausible short- and long-term climate challenges in their communities — where fishing, forestry, tourism and agriculture are economic cogs.

Birkel is a research assistant professor and the Maine State Climatologist based at the Climate Change Institute (CCI) and Mayewski is a Distinguished Maine Professor and director of the CCI.

Maine’s coastal climate is strongly influenced by a number of factors that determine short and long-term changes in climate, they say.

Key factors include El Nino/Southern Oscillation (ENSO), volcanic eruptions and warming in the Arctic associated with increasing greenhouse gas emissions. ENSO is a particularly important feature as El Nino brings warm/dry conditions and La Nina brings cool/wet conditions to Maine.

This pattern of variability oscillates every three to five years. And the three strongest recent El Nino events (1982–83, 1997–98 and 2015–16) occurred approximately 15 years apart.

Birkel and Mayewski analyzed historical climate trends, climate–commodity connections and sources of climate variability that affect Maine to put forth five plausible climate scenarios for 2020–2040.

The scenarios: no additional change to the current “new normal”; moderate warming; another abrupt Arctic warming and even greater Arctic sea ice collapse; cooling from increased volcanic activity; and drying from more frequent and extreme El Nino events.

“Global climate models are well suited for simulating long-term trends under different greenhouse-gas emission pathways, but they do not necessarily resolve regional variability enough to make actionable projections only a few years out,” says Birkel.

“That’s where plausible scenarios based on the historic record come in.”

The coastal region already is experiencing more intense rain events, a longer growing season and increasing temperature extremes, say the researchers.

Since January 1895, the average annual temperature across coastal Maine has increased about 3 degrees Fahrenheit, and total annual precipitation has increased about 6 inches.

Three of the state’s coastal commercial crops — blueberry, apple and cranberry — can be positively and negatively affected by a changing climate.

The average growing season since 2000 has increased by about two weeks in comparison to the 20th century mean. August and September temperatures also have warmed 2–3 degrees Fahrenheit.

While a longer growing season is beneficial to most crops, there are negative impacts of the changing weather, say Birkel and Mayewski.

These include northward migration of pests, extreme rainfall events and more frequent “blocking” patterns in the atmosphere that increase the likelihood of heat waves and drought.

And in the Gulf of Maine, where the sea surface temperature has warmed about 3 degrees Fahrenheit since 1895, circumstances have changed dramatically for lobster and cod.

Other studies have indicated the cod fishery collapsed primarily due to overfishing. But ensuing recovery efforts have not rebuilt the population, as waters in the Gulf of Maine have warmed above the temperature range which cod can tolerate.

Lobster abundance, though, has increased fourfold since the late 1980s largely in connection to warming waters.

Birkel and Mayewski found that increased temperatures in the Gulf of Maine correlate with stronger surface winds in the summer that drive more warm water from the Gulf Stream into the Gulf of Maine.

Changes in atmospheric patterns spanning the Arctic and North Atlantic also are associated with an increase in summer precipitation, especially from 2005 to 2014.

Annual blueberry yield, though strongly impacted by mechanization and other factors, correlates with changes in this large-scale circulation, say Birkel and Mayewski.

The researchers utilized the CCI’s online data tools, including the Climate Reanalyzer and Maine Climate Office websites, to produce the 29-page Coastal Maine Climate Futures document. The report was made possible by support from the Russell Grinnell Memorial Trust.

Stakeholders also are invited to utilize the tools to understand the past and glean insights into possible climate futures.