When Kopp and colleagues charted the sea level rise over the centuries – they went back 3,000 years, but are not confident in the most distant 200 years – they saw Earth’s sea level was on a downward trend until the industrial age.
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Were it not for the effects of global warming, the researchers concluded that sea levels might actually have fallen during the 20th century.
“The 20th century rise was extraordinary in the context of the last three millennia – and the rise over the last two decades has been even faster”, said Robert Kopp, study lead author and an associate professor at Rutgers University. The present, he can confirm, is historically weird.
Feeding the information into simulations for three greenhouse gas scenarios proposed by the Intergovernmental Panel On Climate Change revealed a rise in sea levels of between one and four feet by the year 2100. However, Princeton climate scientist Michael Oppenheimer, who was not involved in the current work but collaborates with Kopp and was his postdoctoral adviser, says that this agreement between approaches still “begs the question of just how much disintegration of the polar ice sheets will contribute to sea level during the 21st century since neither type of model is adequate for capturing this growing and potentially disastrous contribution – and that is ultimately the most important unknown, both with regard to sea level and potentially with respect to the whole field of climate change”.
A view from the air in 2012 shows the destroyed homes left after Hurricane Sandy in Ortley Beach, N.J. If seas continue to rise as projected, another 18 inches of sea level rise will cause major problems, especially with storm surge. If that’s the case, a water-logged Miami will be the tip of the proverbial iceberg. During that time, global sea level really didn’t get much higher or lower than 3 inches above or below the 2,000-year average. Last year was the hottest recorded, easily surpassing the mark set one year earlier.
The implications of rising sea levels are dramatic, threatening to make large swathes of low-lying coastal cities uninhabitable and spark an exodus of people to higher ground.
The study also found significant correlations between lower sea levels during periods of lower air temperatures, Kopp noted. “That’s what our statistical approach allows us to do”, he added.
Instead, global sea level rose by about 14 centimeters, or 5.5 inches, from 1900 to 2000.
The US Environmental Protection Agency estimates that 26,000 square kilometres (10,000 square miles) of land would be lost if global sea levels rise by two feet.
Kopp’s collaborators Klaus Bittermann and Stefan Rahmstorf at the Potsdam Institute for Climate Impact Research in Germany used the study’s global sea-level reconstruction to calculate how temperatures relate to the rate of sea-level change.
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Rutgers says that the database included records from 24 locations around the world and the analysis also tapped 66 tide-gauge records from the last 300 years. That’s because two-thirds of floods since 1950, measured at 27 tidal gauges around the country, might not have spilled over without a push from manmade climate change, according to a new report by the research-and-news nonprofit Climate Central. Led by two scientists from the Potsdam Institute for Climate Impact Research, the report estimates the oceans will swell about a meter by the end of the century if nothing is done to stop climate change.
