IREF readers are familiar with Steven E. Koonin’s moderate positions on global warming and its consequences. Here is a summary of his latest article, which was just published in the Wall Street Journal, about rising sea levels that would threaten New York City. Here too, caution is called for.
To judge this, let’s compare different eras, ours and others where these human influences were much weaker.
A recent report from the National Aeronautics and Space Administration (NOAA) is once again very alarmist: New Yorkers are about to be inundated by rapidly rising seas. A review of the data, however, suggests that such warnings should not be taken at face value.
Sea level has been measured since 1856 at the so-called Battery Park, at the southern tip of Manhattan. We see that it is 19 inches (48 cm) higher today than it was 166 years ago, and therefore has risen on average 3.5 inches (7.62 cm) ) every 30 years. Geological excavations show that the process began about 20,000 years ago when the last great glaciers melted, causing New York’s coastline to recede more than 80 kilometers.
There is no doubt that sea levels measured at the Battery will continue to rise over the next few decades, if only because the land is steadily sinking about 2 inches (5 cm) every 30 years due to factors such as tectonic movement, changes in glacier mass and subsidence. The real question is: will increasing human influences on the climate lead to an acceleration? To judge this, let’s compare different eras, ours and others where these human influences were much weaker.
The graph shows sea level rises year after year since 1920. They have ranged from 1.5 (2 cm) to 6 inches (15 cm). The one observed for the last 30 years, of 5 inches (12 cm), is higher than the average of the century, but is not without precedent and nothing indicates that it will continue.
Sea level has changed no more in recent decades than in the last century
As the Earth warms, fluctuations in sea level at The Battery will depend in part on changes that will occur almost everywhere else: melting of mountain glaciers, Greenland and Antarctica, expansion of oceans, in particular. It is very difficult to predict these changes because many factors are involved in the melting of the ice and the oceans absorb only 0.25% of the heat circulating in the Earth’s climate system. The increases observed during the 30 years of the second half of the 20th century decreased by about an inch (2 cm) due to the impoundments created by the dams and changes in the groundwater system here and there in the world.
Sea level also depends on local upheavals and the sinking of land. The natural variability of winds, currents such as the Gulf Stream, salinity and North Atlantic temperatures, which cause sea level variations along the entire northeast coast of the United States, are decisive factors; but too unstable for climate models to clearly and accurately explain the data shown in the graph.
This does not prevent NASA from taking up in a recent report a study by the National Oceanic and Atmospheric Administration from last February which predicts a rise in sea level at Battery park of one foot (30.4 cm) by at 2050; and this, says NOAA, regardless of the rate of greenhouse gas emissions. But no one is able to say whether these predictions are correct. If New Yorkers can continue to watch the rising waters around them, there is no reason to panic and migrate to higher ground! Sea level has not changed more in recent decades than in the last century. And, while we will have to wait thirty years to find out if NOAA’s predictions of a sea level assessment were accurate, the measurements we make over the next ten years will already tell us how quickly we must erect new dikes.
Article translated and adapted by Nicolas Lecaussin.
