"... ocean levels are set to rise dramatically. According to UCLA scientists, the last time carbon dioxide levels were as high as they are today was 15 million years ago. At that time, the sea level was between 20 and 36 metres higher (75 to 120 feet), there was no permanent ice cap in the arctic, and very little ice in Antarctica or Greenland. That is where we are headed.", as reported over at Culture Change by Keith Farnish and Dmitry Orlov.
So the question is, how soon are we going to see significant sea level rise? Again from the Culture change article;
"There are two schools of thought, but they basically come down to when the temperature of Greenland increases by either 4°C or 8°C above the mean global average of the last 100 years.
Four degrees... haven’t we seen that first figure before? In fact, a global rise of 4 degrees corresponds to a considerably larger rise of Arctic temperatures: conventionally this is between 5 and 6 degrees, but if you look at the 2009 Hadley Centre forecasts, a global rise of 4 degrees actually corresponds to an 8 degree rise across much of Greenland. Pick any number you like, but Greenland is melting."
There is also the considerable mass of the Antarctic ice sheet to consider. As temperature increases are largest at the poles we can't leave Antarctica out of the equation.
"The WAIS (West Antarctic Ice Sheet) is largely below sea level, having over several million years pushed down and scoured out the bedrock beneath it, but because of its huge area, the part of it that is above water still manages to comprise around 10% of the total Antarctic ice volume. If this were to melt then the oceans would rise by another 5 metres, in addition to the thermal expansion of 1.4 metres, plus whatever has been sloughed off the Greenland ice sheet, giving us 13.6 metres, or close to 45 feet."
We've been hearing for years about the breakup of huge sea ice shelves in Antarctica and while these don't raise sea levels they have been serving as a plug on land ice movement to the sea. This means the land ice is accelerating towards it's watery doom, presaging the doom of our coastal cities.
But combining all the science which deals with one or another sea level raising effect is difficult and there is no consensus on an accurate forecast at this time. One researcher says .82 meters another 1.3 meters by 2100. But remember that scientists are conservative folk and their forecast reflect this, even more so when governments get their hands on them, as in the case of the IPCC. The eventual outcome is what's important.
"We know where we are going to end up eventually: at least 20 metres (65 feet) higher. The one thing we still do not know is how long it will take for us to get there.
We could keep waiting for the scientific community to settle on a consensus forecast, but this may take so long that it will have to be delivered through a snorkel. However, we can already observe that the doubling period of scientific climate forecasts is uncomfortably short, and, to provide for a margin of safety, we should at least double the latest estimates. If the latest forecast is for 2 metres this century, let us assume that we will see at least 4, and plan accordingly.
But do the exact forecasts even matter? We already know enough to say that there is a high probability that ocean levels will rise, significantly, within the lifetimes of most of the people alive today, disrupting the patterns of daily life for much of the world's population, which tends to be clustered along the coastlines and the navigable waterways. We also know that ocean levels will continue to rise far into the future, until they are 20 to 36 metres higher than they are today. We know that continuous coastal erosion and salt water inundation, coastal flooding and displacement of coastal populations, which number in the billions, toward higher ground, will be normal and expected. We also know that there is a high chance these changes will occur based on present carbon dioxide levels, regardless of what is being currently proposed by the governments of the world to reduce greenhouse gas emissions."
I personally believe that if I'm given a normal lifespan of 70 years or more I will see at least a meter of sea level rise. I'm hanging on to my investments in property ... far inland. What's your plan?