What causes sea-level rise?
Sea-level rise from global warming happens for two main reasons:
- The first – one that climatologists have predicted for several years – is caused by thermal expansion: warm water takes up more space than cold water. When you increase the temperature of the ocean by a few degrees, it gets a lot bigger; and
- 70% of Earth’s fresh water is locked up in ice, glaciers and ice sheets in Greenland and Antarctica. For a long time, scientists thought that these massive sheets would take a thousand years to melt. We have had to revise our expectations surprisingly quickly as evidence mounts of accelerating melting.
How much will sea level rise and when will it happen?
Scientists and planners have known for more than a decade that the sea level is rising. In 1995, the EPA estimated that a 2-3 foot sea-level rise was possible over the next several generations. Climate change scientists have recently revised their predictions in response to a quicker than expected warming trend. Global warming has accelerated the melting of ice in Greenland, Antarctica, and the Arctic Circle. Glaciers worldwide have shrunk by more than 50%.
Using the latest scientific evidence from the University of Maine’s Climate Change Institute in Orono and others, NRCM used GIS mapping technology to show a one-meter (3-foot) and six- meter (20-foot) sea-level rise.
The NRCM analysis estimates that a one-meter rise would submerge more than 20,000 acres of coastal real estate in Maine; the six-meter rise would inundate more than 128,000 acres. The two scenarios would destroy 53 and 380 miles of roads, respectively.
“If global warming continues unabated, then portions of Maine’s coastline will be forever changed. That is why we are calling for increased efforts at every level to reduce global warming pollution. The most dangerous impacts of sea-level rise can still be avoided, but widespread action is needed now. According to scientists, we have a shrinking window of opportunity to change our course—measured in years not decades,” said Voorhees.
“Just a few years ago, scientists believed that the maximum sea-level rise would be around three feet by 2100. But now a three-foot rise is viewed more as a middle range of what might occur due to global warming,” said Voorhees.
“Based on what we are learning in the polar regions, we must now confront the possibility of a rapid 3-foot sea-level rise caused by melting glaciers,” said Professor Gordon Hamilton of the Climate Change Institute at the University of Maine. “Glaciers in Greenland are changing much faster than we expected just two or three years ago. This should be cause for very serious concern in a state like Maine, with the nation’s longest coastline and many communities built just slightly above sea-level,” said Hamilton.
The technique used by NRCM to show sea-level rise represents a conservative estimate of impact under these two scenarios. In reality, rising seas erode beaches and bluffs much faster than if the sea level was simply rising as in a solid bath tub. The area affected in the one-meter scenario could easily be doubled by storm surges. No erosion or storm surge flooding was modeled in the NRCM analysis, making the actual effects potentially more devastating.
What will the impact be?
Economic impacts could be serious. Businesses could be damaged, real estate lost, transportation infrastructure destroyed, and tourism revenues lost.
- Many parts of Route One would need to be completely rebuilt and re-routed.
- Millions of dollars would be required to rebuild fresh water supplies and wastewater treatment plants.
- The value of damaged and destroyed commercial and residential properties would be enormous. Two neighborhoods in Portland with an assessed value of more than $70 million, East Deering and Baxter Boulevard, would be ruined by a six-meter rise.
- The value of properties along the more affected, and more expensive, south coast would be in the hundreds of millions.
- Because these areas include some of the State’s most important tourist destinations, the economic impact on Maine’s $3.5 billion tourism economy could be incalculable.
Ecological impacts could be severe. Breeding habitat in sand dunes, tidal marshes, and coastal wetlands, used by hundreds of species, could be destroyed. Impacts would be particularly high for some of Maine’s most endangered birds like the Piping Plover, Saltmarsh Sparrow, and Roseate Tern.
“Coastlines have continually changed over the millennia, but this degree of change over the course of decades means that marshes, beaches and other needed habitat will be destroyed before new nesting grounds can be created,” said Jeanette Lovitch, a biologist, birder and business owner from Yarmouth.
“This analysis should be a wake-up call. We still have an opportunity to avert the most serious impacts, but doing so will require increased actions at all levels to curb greenhouse gas emissions,” said Voorhees. “Maine has shown good initial leadership by individuals, cirties like Portland, and by the State – but we need to increase our actions to boost energy efficiency, expand renewable energy, and cut carbon emissions. We all must be part of the solution that will help keep the worst of these scenarios from becoming a reality.”
What can be done to prevent this from happening?
This isn’t something we should be leaving towns to address on their own, the state and the region need to do more to reduce global warming pollution. Cities like Portland are today’s leaders on global warming. We need citizens to get involved in local efforts, and to examine their own lives for ways to reduce global warming pollution.
We can prevent the worst effects modeled here by adopting strong policies at the state level. Sea-level rise caused by global warming is not an unpreventable natural disaster. To prevent global warming from having these devastating impacts, we need to work together to adopt solutions that are already at our finger tips:
- Energy efficiency—the cheapest, cleanest source of energy
- More renewable power, and strong efforts to clean up old fossil-fuel plants
- Cleaner cars, cleaner fuels, and more transit
- Green buildings and sustainable land use practices, which make Maine a nicer, healthier place to live and work.
- Become an NRCM activist and contact your legislators regarding important energy issues.
Why should I care about global warming?
Maine already is seeing the warning signs of global warming, with sea level rise, beach erosion and increased temperatures. Maine’s cold weather sports such as skiing and ice fishing, our forests, our fishing industry, even our maple syrup industry are at risk. For more information check out NRCM’s publication, “Global Warming in Maine: Warning Signs, Winning Solutions.”