Extensive flooding of coastal cities on the way?

The stuff below is the most total and utter rubbish.  It is all based on the expected level of CO2 in the atmosphere.  They assume exactly what is never found:  That temperatures will rise in synchrony with CO2 levels

I append the journal Abstract to the article below.  Note: The "Representative Concentration Pathway" refers to the CO2 concentration in the atmosphere.  There are 4 such pathways, all assuming very different levels of CO2.  It's all guesswork, in other words. The authors below have mostly used the most extreme estimate (8.5).

It's a deliberate attempt at alarmism, not the sort of cautious  and balanced presentation one normally expects in an academic journal article.  They had to use extreme estimates in order to have anything at all to say

With global climate talks kicking off in Marrakech, Morocco on Monday, a new study provides a sobering warning about what may happen to coastal mega-cities if decisive global emissions cuts are not made soon.

Based on a scenario in which countries fail to sharply rein in emissions of global warming pollutants, coastal cities are likely to see the fastest rate of sea level rise in human history before the end of the current century, the study found.

This damaging scenario is not just limited to a future generation in the year 2100 but has already begun.

What's more striking is that the study shows that more than more than 90 percent of the world's coastal areas will see more than the global average sea level rise.

The study paints a particularly dark scenario for the densely populated cities of South and Southeast Asia, where low-lying coastal cities could be eaten away by the sea, displacing millions.

The study, published Monday in the journal Proceedings of the National Academy of Sciences, found that if global warming pushes past 2 degrees Celsius, or 3.6 degrees Fahrenheit, above preindustrial levels, about 80 percent of the global coastline may see more sea level rise than the global average.

The study is the first to make specific sea level rise projections for 136 coastal cities starting with 2 degrees Celsius of warming and above, according to lead author Svetlana Jevrejeva of The National Oceanography Center in Liverpool.

Jevrejeva and her colleagues found that 2 degrees of warming would yield an average global ocean rise of 0.6 feet. But in the sprawling city of Lagos, Nigeria, for example, that much warming would likely cause 0.7 feet of sea level rise with a worst-case-scenario of 1.1 feet.

Two degrees Celsius is also defined as the upper limit to global warming under the Paris Climate Agreement, which went into effect on Nov. 4, but that limit is likely to be reached by 2045, based on emissions trends.

"If the Paris Agreement fails and the worst-case scenario comes to pass, South Florida and the boot of Louisiana would not likely survive this century. Many more places, from Boston to Shanghai, would be gravely threatened,” said Ben Strauss, a sea level rise researcher at the nonprofit group Climate Central who is unaffiliated with the new study.

The meeting in Marrakech is aimed at speeding up emissions cuts and generating more ambitious targets so that the Paris goal is met.

This study asks what would happen to global sea levels if we blow past the target.

If the climate were to warm by 5 degrees Celsius, or 9 degrees Fahrenheit, above preindustrial levels by 2100 — which is roughly the path we're on now — New York City could see more than a meter, or about 3.6 feet, of sea level rise with an even higher upper limit, when factoring in sources of uncertainty.

"If warming continues above 2 degrees Celsius, then, by 2100, sea level will be rising faster than at any time during human civilization," the study says.


Coastal sea level rise with warming above 2 °C

Svetlana Jevrejeva et al.


Two degrees of global warming above the preindustrial level is widely suggested as an appropriate threshold beyond which climate change risks become unacceptably high. This “2 °C” threshold is likely to be reached between 2040 and 2050 for both Representative Concentration Pathway (RCP) 8.5 and 4.5. Resulting sea level rises will not be globally uniform, due to ocean dynamical processes and changes in gravity associated with water mass redistribution. Here we provide probabilistic sea level rise projections for the global coastline with warming above the 2 °C goal. By 2040, with a 2 °C warming under the RCP8.5 scenario, more than 90% of coastal areas will experience sea level rise exceeding the global estimate of 0.2 m, with up to 0.4 m expected along the Atlantic coast of North America and Norway. With a 5 °C rise by 2100, sea level will rise rapidly, reaching 0.9 m (median), and 80% of the coastline will exceed the global sea level rise at the 95th percentile upper limit of 1.8 m. Under RCP8.5, by 2100, New York may expect rises of 1.09 m, Guangzhou may expect rises of 0.91 m, and Lagos may expect rises of 0.90 m, with the 95th percentile upper limit of 2.24 m, 1.93 m, and 1.92 m, respectively. The coastal communities of rapidly expanding cities in the developing world, and vulnerable tropical coastal ecosystems, will have a very limited time after midcentury to adapt to sea level rises unprecedented since the dawn of the Bronze Age.


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