REUTERS: Rising Sea Level Can't Be Stopped -- Only slowed
A Reuters lead story last week out of London, got the key facts about rising sea level dead on: Rising sea level can no longer be stopped, even if we stop all greenhouse gas emissions, though it can be slowed.
That is one of the key points of my forthcoming book: High Tide On Main Street: Rising Sea Level and the Coming Coastal Crisis.
While that truth is a bit depressing, it is, well...the truth. A brief explanation: Sea level has moved up and down hundreds of feet, repeatedly in Earth's history. It adjusts to average global temperature, over the LONG TERM, meaning centuries. The large ice sheets, such as those now atop Greenland and Antarctica melt slowly. The extent and thickness of the ice sheets are the best long term indicator of average global temperature.
Twenty thousand years ago, we were at a "glacial maximum." North America and Europe were covered in ice up to a couple of miles (few km) thick. As those extensive sheets melted, sea level rose almost 400 feet (120m) over some 14,000 years. For the last 6,000 years sea level has been almost fixed. Unfortunately this led us to believe the shoreline did not move, just as our civilization was taking off, during those same millennia.
We have had ice ages every hundred thousand years, for almost three million years now. The 100,000 year cycle splits into about 20,000 years of sea level rise, followed by 80,000 years of sea level fall. Around this century -- more or less -- we were due to start the phase when sea level would go down.
But for the last century it has been rising -- about 8 inches. The rate of rise has almost doubled the last three decades. This melting and rise absolutely correlates with the amount of CO2 we have added to the atmosphere, and the measured increase in atmospheric and ocean temperatures: about eight tenths of a degree C (1.5 degrees F) over the last century.
The problem is that the geologic record says that sea level moves about 65 feet (20m) for each one degree C. We have already warmed the planet almost that much and the rate of warming is accelerating. Predictions are imprecise because of the long lag time for the ice sheets to melt, and the fact that the Earth has never warmed this quickly to our knowledge. Even if it take centuries, the idea of sea level moving 65 feet -- or more -- straight up, and therefore miles inland in most places is a true crisis, to put it mildly. Every coastal city will eventually be underwater, and many along the river banks.
What we do know is that the ice sheets and glaciers respond to warming -- everyone knows that the melting point of ice is very specific. Earth is warming, due to increased amounts of CO2 in the atmosphere. CO2 has been known to act like the glass in a greenhouse, for almost two centuries. That's not an opinion, it's basic physics and chemistry.
While there is enough heat already trapped in the ocean to continue the process of ice sheets melting for at least five hundred years, future levels of greenhouse gas emissions will determine if the rate of warming, and the resulting sea level rise, speeds up, or slows down. That's the message of this short article by Reuters. I am glad to see that it actually got some decent global coverage.
If you want the more thorough explanation, along with the impacts, and what we can do to adapt to the inevitable rising sea level, I hope you buy my forthcoming book. If you want to be on the publication alert list, just send a blank e-mail to: email@example.com
As for the basic situation we are now in about rising sea level and the problems ahead, think of it this way: if you were in a car headed for a crash (or a ship headed for an iceberg) the first thing you do, is bring the gas pedal (throttle) back to neutral, i.e. "take your foot off the gas." That only makes sense to reduce and delary the impact and resulting damage.
It is urgent that our leaders understand the long term implcations of our present energy policy. I urge you to find ways to communicate the imperative to reduce greenhouse gases, AND to begin to adapt to the higher sea levels that are now inevitable.
We have no idea of the virtual tsunami that lies just over the horizon....