Thanks to global warming, we have already started to witness a growing frequency of extreme weather events across the globe. And another such impact is still waiting to unleash its wrath, rising sea level! Melting glaciers, ice sheets, and the thermal expansion of seawater result in a gradual increase of sea levels that will continue for decades even if we bring down the carbon emissions to net zero.
In the last century alone, sea levels have increased by 8-9 inches, and about a third of this has occurred only in the previous two and a half decades. To make matters worse, the latest IPCC report predicted that the rise in sea level would happen at a faster rate in the coming years.
Another research published this week is consistent with the IPCC report and warns that extreme sea levels will become a new norm. The study, led by scientists at the University of Melbourne, shows that extreme sea-level events that used to occur once in 100 years are likely to happen every year by the end of the 21st century!
The study forecasts that due to rising temperatures, extreme sea levels along the world’s coastlines will become 100 times more common in around half of the 7,283 places evaluated. “We estimate that by 2100, around 50% of the 7,000+ locations considered will experience the present-day 100-yr extreme-sea-level event at least once a year, even under 1.5 °C of warming, and often well before the end of the century,” explains the study.
While the study acknowledges the uncertainties involved in predicting the exact frequency of such extreme events, scientists believe that such severe sea level rise will most certainly become more and more frequent. The impact is the most likely outcome of global temperature rise by 1.5 or 2°C, which scientists estimate to be at the bottom end of the range of probable global warming. Unfortunately, these changes could happen sooner than the end of this century; some locations will probably see a 100-fold increase in these events by 2070.
Dr Ebru Kirezci, an ocean engineering researcher and co-author of the study, suggests that the Southern Hemisphere and subtropical regions, the Mediterranean Sea and the Arabian Peninsula, the Pacific Coast of North America’s southern half, and areas such as Hawaii, the Caribbean, the Philippines, and Indonesia will be particularly impacted due to such extreme sea-level events.
“What we can also infer from this study is that most of the eastern, southern and southwestern coastlines of Australia will be impacted with almost an annual frequency of these extreme sea levels by 2100,” Dr Kirezci said. The higher latitudes, northern Pacific Coast of North America, and Pacific Coast of Asia would be less affected.
Dr Claudia Tebaldi, lead author of the study, a climate scientist at the US Department of Energy’s Pacific Northwest National Laboratory, said they studied how much worse the temperatures have to get for the sea level rise to become an annual event. And the results showed that even temperatures not deviating much from the current levels are enough to cause the yearly increase in sea levels.
“This study gives a complete picture around the globe. We were able to look at a wider range of warming levels in very fine spatial detail,” Dr Tebaldi said. The scientists studied the best and worst-case scenarios at 1.5°C and 5°C rises in temperatures compared to pre-industrial levels.
Prof. Ranasinghe, a co-author, explained this with an example, saying that with a 1.5°C rise by 2100, the 100-fold increase in frequency is anticipated to occur between 2070 and 2080 for most tropics and subtropics sites; with warmer trajectories reaching up to 3.0°C by 2100, this 100-fold increase will occur one decade sooner, between 2060 and 2070. And for the highest levels of global warming assessed at 4.0°C and 5.0°C, they forecast that most of these sites will see a 100-fold rise in frequency even sooner, between 2050 and 2060.
More research is needed to better comprehend how the changes would affect specific communities. The team noted that the physical changes described in their study will have various implications at local scales and could vary due to multiple factors such as the site’s vulnerability to rising seas and how prepared the communities are for change.
According to Dr Kirezci, “public policymakers should take note of these studies and work towards improving coastal protection and mitigation measures. Building dykes and sea walls, retreating from shorelines, and deploying early warning systems are some of the steps which can be taken to adapt to this change.”
This study was published in the journal Nature Climate Change earlier this week and can be found here.
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