Monday, August 10, 2009
Chicken Little of the Sea
The sea is rising! The sea rising! Twice in the last couple of months I've encountered people talking about a possible 100 (one hundred) metre (meter) sea level rise in the next one-hundred years. I've even seen one article that showed maps of Australia after a predicted 300m sea level rise. This seemed like a heck of a lot of water, so I wondered if anyone had done the math, volume calculations and so forth. It turns out a good number of people have done the math ...
So let's be boring and talk volumes. There is a lot of ice out there in the world. If all the ice in Greenland was to melt, for example, the global sea levels would rise by 6-7 metres. There's some wiggle room in the numbers because it is hard to accurately gauge the thickness of the ice, but the calculated volumes are all similar. That's quite a rise in sea levels from just one block of ice. It is a very large block of ice though ...
By-the-way, there are climate change deniers who point out that the Greenland ice sheet is actually thickening ... which they use as a 'counter-example' of warming. However, the truth is, as always, more interesting. As the Greenland ice melts around the edges, as ice tends to do, the increase precipitation (rain and snow fall) in Greenland due to the warmer average temperature deposits more ice on the top of the pile. So it is growing thicker, even as it loses mass to melting.
Back to sea level rise. So, all of Greenland equals a 6-7m rise ... this sounds bad. We can add in some more ice ... The Antarctica Peninsula ice would add in about half a metre, and this is about the same amount as all the world's glacier ice. If all the Antarctica ice were to turn to water, the whole continent becoming incontinent as it were, then you are looking at some serious changes ... about 60m in rising sea waters. However, even when you add in all the snow and ice from everywhere in the world, a melted earth, you still don't get to one hundred metres. In fact, you don't get to 90m even when you add in water expansion from temperate rise.
Seventy or so metres of sea rise sounds pretty bad, but remember the entire world has to melt to get this rise. Not a drop left in ice form. This would mean a change in temperature of plus 37oC in various places. As far as I'm aware no-one is suggesting a global temperature rise of 37oC by 2100. If that were to happen, sea level rises would not be our most compelling problem. Building extremely deep underground bunker complexes or leaving the planet would be much higher on our to do list than worrying about the lapping water around our necks.
The actual scientific figures out there estimate a global sea level rise of between 0.1mm (one tenth of a millimeter) to 0.95mm (just under 10 centimetres) a year until 2100 (By scientific I mean from places like the Max Plank Institute and the IPCC (Intergovernmental Panel on Climate Change)). This means that we have a predicted average sea level rise of up-to-a-metre in the next century, but probably less, assuming change continues as predicted. This is 1% or less of the 100m 'prediction' I have been seeing splashed around lately. By the way, the key phrase there is 'average rise' ... individual results may vary.
The odd thing is, a 1m or even half metre sea-level change will have massive consequences ... higher waves, higher flood waters, costal erosion ... but for some reason no one wants to say 'one metre' or 'half-a-metre' or even 'up to a metre' ... it sounds too small. Too tiny to be frightening. So radio, web and TV experts just seem to make up numbers, scary numbers, as it sounds and looks better. Five meters, 10, 25, 50 100, and even 300m ... For example, there's a Google Earth add-on that allows you to change the sea level ... but adding 0.5m to the program changes nothing as the resolution is too small. Instead you are encouraged to enter 50m or 100m to simulate the sea level changes from global warming (indeed there is a popular website of showing generated world maps showing 100m sea level rise), and when you do massive changes occur, but the problem is these numbers are made up. The only basis for entering such large changes is to see large changes on the map ... there's no science behind those numbers, and there's just not enough water out there.
As a contrast, at the end of the last ice age the change is sea levels was about 120m. There was a lot more ice on the planet then (about three times as much as today) and while various kid's films may suggest the melting happened in a hurry, it was a slow change of several thousands of years. This means we currently have media climate 'experts' telling us to expect a change nearly as dramatic as the end of the last ice age to occur thirty times as fast as it did then.... And no-one questions these experts, because to do so is to be labeled a horrid denier of global warming and worse than (insert enemy of the month here). Once these exaggerated figures get out into the public domain they are slavishly copied and repeated without checking.
Don't get me wrong here, I'm not a climate change denier. I'm not saying sea levels are not rising. I'm not saying that even a less-than-half-a-metre change isn't going to have terrible consequencess. I'm not saying something dramatic couldn't happen ... such as a large chunk of the Western Antarctic ice sliding into the water and raising sea levels several metres. I'm just saying that anyone who tells you that the sea level is going to rise 100m in the next century is talking bollocks ... complete and utter, unsubstantiated bollocks.
Artwork by Guy Landry