Sunday, February 25, 2018

Seas Will Rise for 300 Years

And the longer it takes to reduce carbon emissions, the higher they will go.

Seashore [Credit: Erika Maldonado Flickr (CC BY 2.0)] Click to Enlarge.
It's a given of climate change that greenhouse gases emitted today will shape the world for future generations.  But new research underscores just how long those effects will last.

A striking new study published Tuesday in the journal Nature Communications suggests that sea-level rise—one of the biggest consequences of global warming—will still be happening 300 years from now, even if humans stop emitting greenhouse gases before the end of the current century.

What's more, the longer it takes to start reducing global emissions, the higher those future sea levels will be.  The study suggests that 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—sea levels will rise an additional 8 inches by the year 2300.

"The Paris Agreement calls for emissions to peak as soon as possible," researcher Carl-Friedrich Schleussner of the Potsdam Institute for Climate Impact Research, one of the study's co-authors, said in a statement about the new paper.  "This might sound like a hollow phrase to some, but our results show that there are quantifiable consequences of delaying action."

The study emphasizes an important scientific concern about the progression of climate change—that 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—and even if they 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 for curbing emissions now may mitigate sea-level rise in the future.

Read more at Seas Will Rise for 300 Years

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