Rising sea levels for the next 300 years spell out the Doomsday scenario

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Konstantin Sheiko
March 23, 2018

The proponents of the climate change theory argue that greenhouse gases emitted today will shape the world for future generations. New research conducted in this area accentuates just how long those effects will last. A new study published in February in the journal Nature Communications suggests that sea-level rise, being one of the biggest consequences of global warming, will continue for 300 years from now - even if humans stop emitting greenhouse gases before the end of the current century.

The study argues that the longer it takes for humanity to start reducing global emissions, the higher those future sea levels will be. For every additional five years it takes for emissions to peak and start falling - for instance, if emissions were to reach their maximum levels in the year 2030, as opposed to 2025 – the sea level will rise an additional 8 inches by the year 2300. According to the Paris Agreement, emissions must peak as soon as possible.

Despite the fact that it sounded like a hollow phrase to some, the study’s results show that there are clear-cut quantifiable consequences of delaying action. The study emphasizes an important scientific concern about the progression of climate change. Its effects don't always occur immediately, or even quickly in some cases. Even after humans stop emitting greenhouse gases into the atmosphere, global temperatures are expected to continue rising before they finally stabilize, potentially for decades. And even after temperatures stop rising, other effects of climate change may continue to go on for hundreds of years. 

Sea-level rise is one example. Rising seas are caused by the combination of a number of different processes, including the warming of the ocean, which causes the water to expand in volume and the melting of glaciers, particularly from the massive Greenland and Antarctic ice sheets. Both of these processes may continue long after human-caused greenhouse gas emissions have come to a halt. The melting of the ice sheets, in particular, is a process that may be difficult to stop once it's set in motion. 

Even after global temperatures stabilize within the 2-degree Celsius threshold outlined under the Paris climate agreement, the warming that occurs up to that point may destabilize the glaciers to an extent that continued ice loss becomes unstoppable far into the future. In short, scientists generally believe that current greenhouse gas emissions have already committed the world to significant levels of sea-level rise for generations to come. The question is how much, and to what extent different strategies and scenarios for curbing emissions now may mitigate the sea-level rise in the future. 

These scenarios are in keeping with reports from the Intergovernmental Panel on Climate Change. For instance, global emissions could peak in the year 2020 and then fall at a certain rate every year afterward, in order to stabilize temperatures within a 2C threshold. Or they could peak at a later date, in 2030 or even 2035, for instance, and fall at a much faster rate to still meet the target. Generally, each of these trajectories assumes that human-caused emissions must cease entirely by about mid-century. Within these scenarios, the new study finds that sea levels will likely rise by between 2.3 and 4 feet by the year 2300, and they'll likely continue to rise even beyond that point.

But peaking emissions earlier will keep sea levels at the lower end of the spectrum, the research notes. Every five-year delay in the peak generates another 20 centimeters in a sea level rise. According to sea-level expert, the findings are generally consistent with other recent studies. However, all of these scenarios are assuming that the 2C target is met, a goal scientists increasingly believe is slipping out of reach. For the time being, most researchers agree that the individual pledges world nations have submitted under the Paris climate agreement are still not strong enough to meet that goal. 

If temperatures rise beyond that point, the future sea-level rise will be even worse. Other recent research has helped to drive that point home. Several studies have suggested that sea levels are not only rising, but the rate of increase is actually accelerating, rising by an average of about 3 millimeters (around one-tenth of an inch) per year since the 1990s, and that the rate is gradually speeding up. If the process continues at its current rate, sea levels could rise by more than 2 feet by the end of this century alone. 

Other recent studies have also suggested that previous estimates of sea-level rise, under a variety of future climate scenarios, may be too modest. Under severe climate change scenarios, these new studies suggest that sea levels could rise by more than 4 feet by the end of the century. But while the new study reaffirms that climate change carries consequences for hundreds of years to come, climate targets notwithstanding, it also emphasizes that earlier, more aggressive climate action now may still improve life for generations yet to be born. 

The largest emitters of carbon in the world today are China (28.21%), USA (15.99%), India (6.24%), Russia (4.53%), Japan (3.67%), Germany (2.23%), Korea (1.75%), Iran (1.72%), Canada (1.71%) and Saudi Arabia (1.56%). Australia, a huge country with abundant solar and wind resources and relatively tiny population, emits 1.33%, which makes Australia, along with the USA, one of the highest emitters in the world per capita. 

Photo via Wikipedia Commons / Tomasz Sienicki

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