
(Image from Erik Kolstad under a Creative Commons license)
When last weekend’s Chilean earthquake sent people across the Pacific rim scrambling to deal with the risk of a tsunami, there was an added danger.
It was a “King Tide” – the location of the sun and the moon meant their gravitational pull was at its maximum. That, combined with the warmth of the ocean water (warm water expands), meant that low-lying areas were in even more danger of being swamped.
The Chile quake tsunami ended up being pretty mild, but this just highlights a question that most people don’t think about: Why is sea level rise such a big deal?
The question
You’ve probably seen estimates like this:
World sea levels rose 3.1 millimetres (about a tenth of an inch) per year from 1993 to 2003, according to the UN’s Intergovernmental Panel on Climate Change (you remember them – they shared the 2007 Nobel Peace Prize with Al Gore). Extrapolating forward, the group estimates global sea levels will rise between 9 and 88 cm (between about 3 inches and three feet) by 2100.
Doesn’t sound like much, does it?
There are some very good reasons you SHOULD be concerned.
The law of averages
Consider: If I told you we could keep your house at an average temperature of 72 degrees, you’d be pretty happy with that, right? That’s a comfortable temperature.
But if I told you that the average temperature would be 72 degrees, but in some parts of the house, the temperature could drop to 32 degrees, and other places would sometimes hit 212 degrees for a few minutes at a time, that wouldn’t be so good, would it? That’s far from comfortable - in fact it’s dangerous.
Averages are funny that way.
... A 2006 study by Australian oceanographers found the rise was much higher, almost one inch every year, in parts of the western Pacific and Indian oceans.
“It turns out the ocean sloshes around,” said the University of Tasmania’s Nathaniel Bindoff, a lead author on oceans in the U.N. reports. “It’s moving, and so on a regional basis the ocean’s movement is causing sea-level variations, ups and downs.
So while the average isn’t enough to cause concern, it’s the extremes we have to worry about – and there, things are getting kind of crazy.
Waves are getting bigger
When you put more energy into a system, you get… more energy in the system.
Just a few years ago, the maximum wave height during winter storms that was expected to hit the Oregon coast was 33 feet. That’s enough to cause serious damage, but people can prepare for it.
But a new study was just completed, and it showed the maximum was up to 46 feet! That’s a 40 percent increase – and it means that all the preparations people have been doing for the past 100 years to protect themselves are useless. There’s a good chance that killer waves will hit sometime in the next few years - eroding coastlines, and smashing docks, houses, and sea-side industries.
And we’re just getting started. The non-partisan Cayman Institute estimates that the cost of rising oceans over the next 40 years will hit an incredible $28 trillion dollars. Most of the mega-cities around the word are seaports, and rising waters of even just a few feet will have a huge impact on port facilities, beachside hotels and resorts, public buildings, and private housing.
For the U.S., the Heinz Center figures that just from homes lost to coastal erosion we’re looking at $530 million per year.
Arctic melting may add to that cost as well.
It’s happening now
Low-lying islands are already seeing damage, like the Pacific nation of Kiribati.
For nations and communities that sit only a few metres above sea level, even small ocean rises engulf their land and send destructive salty water into their food supply, leaving residents with little choice but to flee…
As sea levels have crept higher, the coasts have eroded, corals have been bleached, and islanders’ staple foods such as the giant Babai taro, coconut and banana are unable to grow in salty soil.
Another place the rising waters are already causing damage: Australia’s Torres Straights Islands. Here, too, it’s the extremes. Most days there’s nothing to worry about – but every so often king tides create dangerously high surges that sweep over shoreline houses, docks and buildings.
The ocean is life to these islanders, most of whom make a living by fishing. But now they’re being forced to move to higher ground – if they can find some. A few of the islands are just low-lying stretches of mud that barely project above sea level. Seriously high tides can swamp them.
Places like the Torres Straights Islands are the canaries in our global coal mine. The problem can only get worse. Imagine if every coastal road had to relocated inland, every coastal railroad and pipeline… every city! We’re not that different from the islanders – the vast majority of our population lives near the coast. While the displaced islanders only number in the thousands, in low-lying places like Bangladesh or Florida, the numbers will be in the tens of millions.
We’re still learning just how bad things could get.
Now for the next piece of bad news: When the IPCC made its estimate (the one at the top of the article), it was ONLY based on the expansion of seawater due to warming, plus melting from Himalayan and Andean glaciers. Three years ago, there wasn’t enough data to make any estimates on how much water was flowing into the oceans from melting glaciers in Greenland and Antarctica.
Thanks to satellite images and ground-based research, scientists now think they’re beginning to understand what’s happening in those huge ice-fields, and it’s not good. They now think we could be looking at 1.5 meters (4.5 feet) or higher. And again, that’s on average – some places will be much higher. And it’s just an estimate – meaning it could go lower, or much higher. Taken together, that’s a recipe for disastrous flooding for coastal cities like London, Miami, Amsterdam, New Orleans… and the potential for even more trillions of dollars in damage.
And that’s still a preliminary estimate. We know how bad the Greenland melt-off appears to be at the moment, and it’s much worse than we thought it was just three years ago - we have no idea how bad it will get in reality. For instance, the National Center for Atmospheric Research thinks the Northeastern US in particular could be hit by sea level rises a foot or two higher than the global average because of ocean circulation patterns.
Keep that in mind when you see headlines like “Sea Level Could Rise By 1 Meter By 2100, Experts Say”. That does NOT mean that 1 meter is the worst case situation; in science-speak, that figure is the MOST LIKELY situation, based on our current knowledge.
The actual situation could be much, much worse.
(Originally appeared at Tenthmil.com)