Wednesday, June 27, 2012

A Rising Tide Drowns All Cities

The tremendous rain and flooding in Florida, the fires scorching across Colorado, all  Although more Americans are making the connection to the Climate Crisis, there's still room for denial.

But sea level rise...That's a little different.  There are other ways to account for it, of course, but rising sea levels was probably the first predicted effect of the Climate Crisis that got lodged in the public memory.

So now it's not just the kind of weather the Climate Crisis models have predicted.  It's rising sea levels--and one place where they are rising much faster that the global average is the East Coast of the United States.

That's "are rising," according to a new study.  Sure, another new study, but this one is a little different:

   "Computer models long have projected higher levels along parts of the East Coast because of changes in ocean currents from global warming, but this is the first study to show that's already happened."

Of course it's a modest rise, and only one of many predicted global heating effects being observed and reported.  But models show that levels affecting  New York City, Boston and Washington, D.C.  will rise twice as much as elsewhere on the East Coast.

Here's the thing about sea levels rising that maybe everybody doesn't get (I certainly didn't fully appreciate it.)  A sea level rise of five feet does not mean that five feet of beach are going to get washed away.  It means that the sea is going to come into land and flood areas that are less than five feet above sea level, potentially for miles and miles inland, depending on how high the land gets--and even then the sea could tumble through low-lying valleys to form new rivers and lakes. 

That means that stuff that's five feet above current sea level will be totally underwater.  But engineers suggest that a sea level rise of only eight inches could cause millions of dollars of damage in New York.

Current models of how high the rises will be are imprecise, and usually conservative.  Some of the latest suggest 3-5 feet for parts of the East and West Coasts of the US by the end of the century.  Along the West Coast now, beach erosion (caused by a number of factors) is so severe that some communities are wondering whether to just relocate.   But--to use an ironic metaphor--that's probably just the tip of the iceberg.

In an interview Kim Stanley Robinson suggests that if global heating continues and the major ice sheets slide into the sea, sea levels could rise by 30 or 40 feet in a few hundred years.  (He sets his new novel--cleverly called 2312--three hundred years in the future, and posits a 30 foot rise, which transforms New York City into Venice.)   If methane under the ice is released, the planet is cooked, and if all the ice melts, the total rise could be 270 feet.   That's enough to put the state of Florida underwater.

The National Mall in Washington, D.C. is about ten feet above sea level.  The Central Valley of California, far from the coast, could be flooded by a 35 foot rise, creating an inland sea (which it was long ago.) 

It's even likely that with a significant sea level rise, most if not all of the world's beaches would be gone.  There would be no beach to walk on, for a million years or more.

The ramifications are huge, but maybe that one thing is enough to contemplate for now.   

1 comment:

Captain Future said...

I got a comment with one substantive point: that beaches can come back in a thousand years, not a million. I feel a lot better, don't you? The estimate of a million or two million years comes from this same Kim Stanley Robinson interview.