Threat of Sea Level Rise

Sea level rise.
As greenhouse gas emissions have increased since the Industrial Revolution, both the earth’s atmosphere and its oceans have warmed.
Since 1880, the average sea level has risen by about 1.6 mm (0.06 inches) per year. However, this rate has not been constant. New research by NASA’s Jet Propulsion Laboratory shows that during that 140 year period, different effects have contributed to sea level rise. During the early period, prior to the 1950s, the rise was primarily due to melting of glaciers and the Greenland ice sheet. During the 1970s, a worldwide construction of dams reduced surface runoff into the oceans and the sea level rise slowed. Beginning in 1990, sea level rise accelerated, due to greater melting of Greenland and Antarctic ice sheets, glaciers, and a new affect, thermal expansion caused by warming of the ocean. By 2020, 40% of sea level rise was due to thermal expansion and 60% to ice melting. Between 1990 and 2020 the average rate of sea level rise more than doubled to 3.3 mm (0.13 inches) per year.
Greenland ice at the point of no return.
In 2019, Greenland lost a record amount of ice—586 billion tons, or enough to cover California under more than 4 feet of water. The 2019 Greenland ice melt alone added 1.5 mm (0.06 inches) to sea level rise that year. In August 2020, results of a new study based on 34 years of satellite measurements on 234 Greenland glaciers, was made public. The researchers found that the snowfall that replenishes the ice can no longer keep up with the melting. “Greenland’s disappearing ice sheet is a problem for all of humanity,” researchers said.
Also, the Antarctic summer season of 2019-2020 has seen the hottest temperatures on record. Ice melting has accelerated in both the Arctic and Antarctic.
Current effects.
The effects of sea level rise are already being felt in low-lying islands and coastal areas around the world. The evidence includes increased coastal flooding and salt water intrusion in ground water. As the sea rises, storms and high tides increase coastal flooding and erosion, ultimately destroying homes and crops in low lying areas. According to NASA satellite measurements, sea level rise is now averaging 3.3 mm/year. This rate would lead to an additional increase of 100 mm (0.1 meter or 4 inches) by 2050. Near Miami, sea level buoys have measured an 8 inch rise since 1950. The sea level there is now rising at a rate of one inch every three years. The state is anticipating spending $4 billion on mitigation measures to protect sewage systems, raising roads, storm water improvements, and seawalls. These estimates of sea level rise could be low.
California example.
The California Legislative Analyst’s Office recently issued a report that sea level rise will likely put at least $8 billion of property underwater by 2050 and could affect tens of thousands of jobs and billions of dollars in gross domestic product. Besides properties put underwater, at least $6 billion in additional property will be in jeopardy of flooding during King tides and storm surges—as has already been evident in Newport Beach, Seal Beach, Capistrano Beach, Delmar, and other locations up and down the California coast. Rising seas are causing coastal erosion, beaches are shrinking, oceanfront homes in San Clemente and other locations have been damaged by wave action, and three beachgoers were killed when a weakened bluff collapsed and buried them at Encinitas. In addition, rising seas threaten coastal infrastructure, including highways and the railroad at San Clemente.
How much higher could it go?
There is considerable uncertainty as to how much the sea level will rise by the end of this century. It will largely depend on the rate at which ice caps melt in the Artic, Greenland, and Antarctica. According to the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment report issued in 2014, the sea level rise could be much higher, perhaps as much as 0.15-0.3 m (6-12 inches) by 2050. With extreme melting of Greenland ice, sea level rise could reach 2.4 m (8 feet) by 2100.
Can we stop sea level rise?
What if we want to curtail sea level rise? Can it be done? Problem: we’re able to add greenhouse gases to the atmosphere, but we can’t remove them. Even if we could stop emitting greenhouse gases soon, CO2 concentration in the atmosphere (now over 400 ppm) will remain elevated for decades or more until it is reduced through natural processes that take a long time. The real and present danger faced by the world is augmented by two other phenomena:

  • The first is latency—there will be delayed effects caused by the greenhouse gases already in the atmosphere. The earth’s temperature will remain elevated and polar and Greenland ice will continue to melt.
  • The second is the danger of reaching a tipping point—such as the release of methane, a greenhouse gas, due to the accelerated permafrost melting. This could be a powerful feedback effect having an irreversible effect on increasing global warming, causing more melting of the permafrost, further increasing temperature, etc.

Even if we start taking action soon, it will take a long time to reduce the rate at which ice is melting. Meanwhile, we’ll face catastrophic loss of life and property damage in all the coastal areas of the world.

Craig Smith and Bill Fletcher

Reaching Net Zero: What it Takes to Solve the Global Climate Crisis

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