How much sea level rise do you think is happening and how much of that is natural?
Do you have any idea what factors are at work to cause sea level rise other than warming?
Hi Tim,
I've got to do some more homework on your first question.
The second question I am not going to do any homework... Instead I hope to give you enough to make you aware how complicated it is and why scientists uses supercomputers to model this. And I do this by listing some of the factors at play, as you requested.
- When it gets warmer, ice will melt. Meltwater will of course result in an increase in seawater.
- Warmer air can contain more water vapor. As a matter of fact, for every 1 degree C the temperature increases, the air can contain 7% more water vapor. And with the predicted temperature increase of 4% this means that the atmosphere can contain 28% more water vapor. 27% is a LOT. More water in the air means less water in the sea, so this is lowering the sea-level.
- Warm water expands. This means that when the oceans get warmer, the water expands and since it can not go down or left or right it has to go up. And yes, this means that it is a contributor to sea-level rise.
- Landmasses will start to rise when the ice on top of them is absent. The loss of weight causes the land to rise. As a matter of fact, many areas of land are still rising today because of the decrease in weight after loosing all the ice during the last ice age.
- There is talk about runway effects. This can easily be dramatized for a Hollywood movie, but it true, in theory, that this can happen. Let me give you one example how one side effect helps accelerate the main effect. When ice melts it gets dirty. We've all seen that. The beautiful white snow we remember from early winter is nearly black by the end of spring. Well, if you had a lot of snow that is of course. But that is what we are talking about here right. A lot of snow and ice. Now, in Greenland, the same thing is happening of course. So because it gets a little bit warmer, the ice starts to melt end turns darker. The more ice melts, the darker it gets. Because the ice will melt and flow away and or evaporate and leave behind much of the dirt that colors the ice. Much of the dirt will stay in place however. And this means that the surface is getting darker. This means less light is reflected and more heat is absorbed. And this results in more melting because of the higher temperature.
- The CO2 content of both the air and the water also have an impact on the evaporation rate and the amount of water the air can contain.
And to make matters even more complicated, the sea-level rise is not uniform over the planet. Some areas will see more rise than other areas. This is not something that is often discussed, but it is there.
I guess what I am trying to say is that it is very complicated science. Scientists can make predictions, but they are not very accurate. But the trend they are predicting is accurate. The trend is melt and temperature increase. Unfortunately, it is this uncertainty which gives the deniers a say when they pull data out of context.
Joey