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Rising Sea Levels: Disappearing Islands & Underestimation

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Word came yesterday of an island in the Bay of Bengal that has quietly slipped beneath rising seas.  New Moore Island was a rocky island that was 2 miles long and 1.5 miles wide.  This isn’t the first island to succumb to rising sea levels, nor will it be the last, especially since we continue to belch greenhouse gas pollution into the atmosphere.  Indeed, 10 additional islands in the same area continue to face submersion in the near future.  This news isn’t a surprise to any reputable scientist who has studied climate change, nor to any activist who has followed the state of the science.

Also unsurprisingly, Sen. James Inhofe’s family was not photographed on New Moore Island constructing a building in further efforts to misinform the fringe anti-science crowd.  I’m sure the lunatic Senator would cite his favorite conspiracy of global economic domination as the real topic to be discussed.  It wasn’t his island that disappeared, after all.  You’ll also note that the disappearing islands don’t garner much corporate media attention.  Since the stenographers look for controversy, there must be a lack of dimwits who are willing to go record disputing these events.

A real-world concern is low-lying areas around the world.  As sea levels continue to rise, due more and more to our species’ climate-forcing pollution, populations will be displaced.  A nearby island’s inhabitants already moved in 1996.  Bangladesh remains a prime concern in the next 25-50 years.  18% of the country’s coastal area is projected to be impacted by a 1m sea level rise, forcing 20 million people to move inland.  By comparison, 150,000-300,000 residents of the Gulf Coast were forced to permanently move in the aftermath of Hurricane Katrina (accurate numbers of impacted people are very hard to come by).  Given the disruption that population shift caused in a “first-world nation”, what will 20 million people moving do to Bangladesh, one of the poorest nations on Earth, as well as nuclear-armed neighbor India?  Does Sen. Inhofe care to contend that climate change poses no security threat to the U.S.?

The Science

The article also mentions trends in sea level rise.  That ties in nicely with a Newsweek article from yesterday that discussed how predictions of sea level rise contain errors.  Those errors are not what you might think, as I discuss in more detail below.

The article points out that in the last few decades of the 20th century, sea level rise was on the order of 3mm (0.12 inches) per year.  If that rate were held constant year after year through 2100, sea levels would be about 12 inches, or 1 foot, higher than they were in 2000.  That would actually be a pretty big difference to low-lying areas like Bangladesh and our Gulf Coast, among others.  The article continues by noting that sea level rise in the past decade (2000-2009) slightly higher than the 1990s: 5mm (.2 inches) per year.  That’s not a big change in absolute terms, but what would 100 years of 5mm rise total?  20 inches.  All of a sudden, instead of “only” 1 foot of sea level rise, we’re talking about 1.67 feet.

So the rate of sea level rise is increasing with time, which means the response to our climate forcing isn’t linear, it’s non-linear.  That non-linearity introduces uncertainty in predictions of sea level rise throughout the century.  There is a higher likelihood that the rate of sea level rise will continue to increase decade after decade.  The 2010s rise will probably be higher than the 2000s and so on.

To more fully understand the risk posed, it is important to realize that the 2007 IPCC Report underestimated 21st century sea level rise.  Errors exist in the official predictions decided upon for the report – errors that carry a higher cost to global societies than overestimates would.  This is one of the real scandals of the IPCC’s 4AR.  It is quite different than the fake crap climate change deniers have made up in the past year.

Let me point out that the IPCC is, by nature, more conservative in their reports than most people realize – not conservative like U.S. politics conservative, but conservative in the dictionary sense of the word.  Their official predictions are based off the highest confidence scenarios at the time the report was put together.  Unfortunately, many important causes and feedbacks of sea level rise were not incorporated in the last report because there was a relative lack of peer-reviewed science.  More work has been done in these areas in the time since, but the causes remain comparatively under-researched.

Okay, given all that background, what did the IPCC report include?  It’s a little complex.  First, a global average temperature rise of 6.4C was identified.  For the sea level prediction however, a temperature rise of only 5.2C.  The sea level rise value was 10-23″.  The estimate based on the 6.4C warming scenario would include an additional 6″ of sea level rise.  Add in the dates considered (actually 2095 instead of 2100) and an additional 2″ can be included.

Moreover, sea levels have risen 50% more in the past 40 years than the models used to generate forecasts for the IPCC.  So without anything else affecting the prediction, the 10-23″ values are likely too low.  All of a sudden, the cited minimum of 18″ is looking like a pretty rosy forecast compared to what is likelier to occur.

The effort to reduce our pollution to levels required to minimize future climate change effects would obviously benefit from communicating the most accurate predictions of future conditions.  Policy makers cannot effectively plan for the future if they don’t know with high confidence what their lack of action would produce.  By purposefully underestimating pollution and temperature scenarios, the IPCC does itself and the planet a huge disservice.  It would be far better to use scenarios that more closely estimate our actual impacts.  A growing number of predictions have been shown to be out of date and inadequate much sooner after their release than they should be.  There is greater risk in continuing within that paradigm than recognizing the deficiencies of the process to date and making necessary adjustments.

Cross-posted at SquareState.


One thought on “Rising Sea Levels: Disappearing Islands & Underestimation

  1. thanks, i am writing an essay about rising sea level, and im so happy right now to found a perfect information.iwill write like refers to weatherdem’s weblog. thank you!

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