Global Warming: Rising Seas
How much could sea levels rise if Antarctica and Greenland melt or break up?
If the Greenland ice sheet and the West Antarctic ice sheet were to melt, we would get a very large sea level rise. It would not happen immediately, it would play out over the course of centuries, perhaps even over a millennium or two. But in the process, sea level could rise as much as three, four, five, six feet per century. And that's a huge amount. Just to give you an idea, sea level only went up about half a foot in the past century. And it already is creating problems of erosion along our beaches. For every foot that sea level rises on the east coast, about a hundred feet of beach is lost to erosion and submergence. So this is a very, very costly and expensive change. We can barely deal with the kind of sea level rise we're having now. It would be really irresponsible to let a sea level rise. It could be ten times larger occurring in the future.
Why do warmer ocean temperatures make storms more powerful?
Storms like hurricanes draw their energy from the sea surface. As the sea surface warms it provides more energy they can be plumed into such storms. It appears the hurricanes - particularly North Atlantic hurricanes - have got stronger as the earth is warmer. The projections are now that hurricane will continue to get stronger in the future as the green house gases increase.
How is global warming linked to the increasing intensity of hurricanes?
At this point, we know of no evidence that global warming will increase the number of hurricanes, or that it has. In fact, some models predict a slight decrease in the number of hurricanes. What global warming is projected to do is increase the intensity or strength of the hurricanes that we do get. There has already been a shift from category 1 and 2 hurricanes, with less of them, and more category 4 and 5 hurricanes, the really devastating ones, like Hurricane Katrina.
What is the "global ocean conveyer belt" and why are scientists so concerned about it?
There's a massive world girdling current that takes surface ocean water from the warm tropics up towards Greenland. It's salty because it's been exposed to warm sunlight through that whole transit and when it gets to Greenland, the saltiness makes it very dense, very heavy, so when it cools it sinks like a stone to the bottom of the ocean. That creates what's called a conveyer belt, because then you have surface water that's moved from the tropics to the Arctic, sunk fast and then it crawls or creeps along the ocean bottom and comes up in other places, like around Antarctica. And in that way, we get a global circulation that moves salt and water and heat all around the planet. The concern is that global warming, through a variety of mechanisms, will slow and ultimately stop that current and that could create reverberations in the climate worldwide. And at this point, we don't understand exactly what the consequences would be.
