19 April 2023 – by Cosmo Sanderson
An “unprecedented” rise in sea levels on the US southeastern and Gulf Coasts is fuelling catastrophic flooding, according to new research – with one study finding the trend represents a threat to “national security.”
Two studies published in the last two months paint an alarming picture for the millions of Americans living on those coastlines, including in major cities such as Miami, New Orleans and Houston.
One study published in Nature by researchers from Tulane University, New Orleans, found that sea levels have risen roughly a centimetre per year on the southeastern and Gulf Coasts since 2010 – around 12 centimetres in total.
The researchers said this was “unprecedented in at least 120 years.”
By comparison, global sea levels have risen around 3.6 millimetres annually since the early 1990s, according to figures from the US Environmental Protection Agency.
The study found that the drastic sea level rise was caused by an unfortunate combination of man-made global warming and natural variations in the system of currents in the Atlantic.
This rise has led to “exponential increases” in flooding and “increased damages due to major storms such as hurricanes Katrina and Sandy, and the prospect of accelerating land loss in the most vulnerable settings.”
The study says these examples illustrate that further increases in the rate of sea level rise, particularly rapid ones, “threaten the national security of the US”.
Another study published last month in the Journal of Climate by a team from the University of Arizona also found a “rapid” acceleration of sea level rise along the same coastlines since 2010, an “extreme” departure from the long-term trend.
This coincided with “record-breaking” North Atlantic hurricane seasons in recent years, the study found. As in the other study, researchers found worsened coastal flooding due to the storms and exacerbated the damage caused. Last year’s Hurricane Ian racked up around US$113 billion in damages in the US alone.
United Nations secretary general António Guterres recently warned that rising sea levels could cause climate migration on a “biblical scale”. And this is not limited to developing nations. One of the US states included in the recent studies, Louisiana, is already the home of what are reportedly the first climate migrants in the country.
Another recent study found that US households on the Atlantic coast are moving inland following natural disasters, but people on lower incomes are being left behind.
