Sea Level — A S.W.A.G. Game

Sea level has been rising steadily since the end of the little ice age some 250 years ago.  It has been averaging about .2 mm per year or about 7 inches per century.  The rate of change has been surprisingly stable as this chart of San Francisco demonstrates:

Sea level in San Francisco has been trending downward since 1998.  This second chart of the same information makes it a bit easier to see the recent decline:

So if carbon dioxide in the atmosphere has been steadily rising, and the world is a degree warmer than it was 200 years ago, why has sea level has not been rising since it peaked in 1998?

Sea level is a trailing rather than a leading indicator of climate.  And the delay can be as much as a thousand years!  The world warms and then the ice melts.  As fresh water stored over land decreases, sea level rises.  If it stays warm long enough, the deep oceans begin to warm.  As they warm, they expand and sea level rises even more.

The current rising sea level process began about 20,000 years ago as we came out of the last ice age cold cycle.  Here is a chart of that rise in sea level:

Temperature in the Holocene peaked about 10,000 years ago as this chart demonstrates:

The world is a bit cooler than it was 10,000 years ago.  Sea level has been slowly rising the entire period.  Imagine the world of 130,000 years ago when it was much warmer than it is today.

And finally we’ll look at a chart prepared of a Greenland Ice Core:

Greenland is in a cool cycle right now.  It’s a bit warmer than it was a few hundred years ago, but the current period is cold for Greenland in the last 10,000 years.  Greenland is some 2 degrees C cooler than it was just 3000 years ago.  It is worth noting that according to the National Snow and Ice Data Center Greenland has been covered in ice for 18 million years.

When I look at the last two charts I must give Mother Nature her due.  Sea level has been rising since we came out of the last ice age some 20,000 years ago.   And that’s a good thing!   We don’t want the climate we had even 15,000 years ago.  Sure we had lots more land above sea level, but much of it was frozen.   Think Greenland …then imagine the Northeastern USA and you’ll get the idea.

The IPCC appears to be ready to predict (in their 2014 Climate Report) a rise in sea level of from 10 inches to 3 feet and they attribute it to man caused events (according to a NY Times article).   I suspect wild ass guessing.

Changes in sea level we see in the next 86 years are more likely than not a function of the climate we have been having for thousands of years.  The IPCC thinks most variation seen before 1950 is natural climate variation. That’s a lot of change.  How do they know the current changes are not natural climate variation.  How can they know?

One tenet of the IPCC climate change group is that it is cheaper to try to mitigate climate change than it is to adjust to it.  I’m not so sure, I fear they underestimate nature.

  • When I look at the San Francisco chart I see a relatively steady increase since the beginning of the chart in 1850.
  • When I look at the Greenland chart, I see lots on natural climate variation.   Greenland has been lots warmer in the recent past than is today…and that was a natural event.  Will carbon dioxide make it warmer than it otherwise would be. Probably.  But it could get lots colder soon too if history is a guide.  How much of any short term  change is natural and how much is man caused?  I don’t know.
  • When I look at the last 150,000 years I’m glad we live in the warm time we live in.

When I step back and look at the big picture…a steady increase in sea level seems possible as long as we don’t start another ice age cool cycle.  It could be accelerated by an increase in melting from Greenland and Antarctica.  Greenland had an average melt year in 2013 and Antarctic Ice has been actually increasing in recent years.   Sea level has been declining since 1998.

What will the future bring?   I don’t know but I do know this:   Many of the changes in sea level that are a result of today’s weather will show up hundreds of years from now….even if the IPCC is right.

And when I look at the IPCC….I see guessing…..wild ass guessing.


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