THE thread for climate skeptics.

[shunyadragon]

Perhaps you should treat this problem as an opportunity. Think of the benefits of wiping away Miami, Macau, Amsterdam, Panama, Brunei, Tripoli, Bangkok and of course Washington DC, which is only 7ft above sea level

. . . and my North Carolina Piedmont property would become prime water front real estate.

[TheLurch]

Exactly my question. If the massive ice sheets were basically melted, and the sea level raised that much that quickly, and it hasn't frozen back to prior levels, like when Canada was under ice, why should we expect a similar rapid changes as from 8K-7K years? It just seems to me that good ol' Mother Nature can do a far better job at raising the sea levels than humans are being accused of.

You seem to think it's a binary situation - ice or not as much ice. Reality is far more graded than that.

The reason we can see a repeat has to do with the topography of Antarctica. There are several ice filled basins that extend from the coast deep into the interior, all of which are below sea level. The ice within them is piled several kilometers above sea level.

Right now, the site where these meet the coast has what's called a "grounding line" - an area where there are features that are close to sea level, and the ice sits on that relatively stably. That's because the weight of ice above sea level is enough to force the entire ice sheet onto the ocean floor (which again, is relatively shallow at the site), even though water is more dense than ice, and would naturally float it off the grounding line.

Two things can happen to destabilize this: either the ice above thins so that there's not enough weight to force it to the bottom of the ocean, or warm water gets to the base of the ice at the grounding line. When this happens, the ice floats off and breaks up rapidly, and the whole thing quickly retreats back to the next grounding line. (We can see things like this in sediment records, and have watched it happen in Greenland).

The problem with lots of Antarctica: there are only a couple of grounding lines left before you get to the deep basins in the interior. In one case, there are none. If sea water invades those deep basins, then the whole thing breaks up rapidly, dumping those several-km high chunks of ice into the ocean. You get rapid sea level rise of a couple of meters - but that's just if a single basin goes. If several of them go in quick succession or there's some sort of chain reaction (the rise in sea level destabilizes other grounding lines), then we can get over 10 meters in a few centuries.

That's what the worry is.

Incidentally, this is not the mechanism by which there was rapid sea level rise at the end of the ice age. For that, look into the draining of Lake Agassiz.

[seer]

Antarctica and Greenland still have substantial Ice reserves. Where they all to melt, the sea levels would rise an additional 230 feet according to the sources I checked before writing this reply. That is quite a bit, though only about .6 what we saw after the ice age (380+ feet).

This is exactly what I think the problem is, these predictions. How much has the sea level risen in the last 130 years or so since the industrial revolution began? Inches, feet? And I can remember 12 years or so ago being told that Atlantic storms (hurricanes) would become more intense and more frequent - and just the opposite has happened. And on a personal observation, where I have been going to the ocean for 50+ years there hasn't been any change in the ocean level. On high tide it still comes to a certain point and at low tide. There could have been an inch or two of change but certainly not a foot or feet.

[TheLurch]

This is exactly what I think the problem is, these predictions. How much has the sea level risen in the last 130 years or so since the industrial revolution began? Inches, feet?

A bit over a foot. It's going up by a bit more than an inch a decade at the moment, and accelerating.

And I can remember 12 years or so ago being told that Atlantic storms (hurricanes) would become more intense and more frequent - and just the opposite has happened.

That's not the opposite of what happened. Fewer have made landfall in the US, but hurricanes have changed. We're not seeing an increase in numbers (i can go into detail on this if you'd like), but we are seeing an increase of the category 4 and 5 storms.

And on a personal observation, where I have been going to the ocean for 50+ years there hasn't been any change in the ocean level. On high tide it still comes to a certain point and at low tide. There could have been an inch or two of change but certainly not a foot or feet.

Your personal observations may depend on how old you are, may reflect local variations in sea level rise (which exist), or may simply not reflect reality.

Have a look at the table at the end of this NOAA report on nuisance flooding:
http://www.noaanews.noaa.gov/stories...20Flooding.pdf

Nuisance flooding is caused by a mix of local sinking of the ground, and climate driven sea level rise. And it's happening much more often, as that table shows. But the magnitude of the increase varies from place to place. Wilmington, NC has seen a 40-fold increase; Providence RI has seen none. So you may just happen to be going to a place where the difference isn't as pronounced.

[Leonhard]

How much has the sea level risen in the last 130 years or so since the industrial revolution began? Inches, feet?

Here you go sir. The answer is almost 8 inches, about 0.6 feet.

[Bill the Cat]

Antarctica and Greenland still have substantial Ice reserves. Where they all to melt, the sea levels would rise an additional 230 feet according to the sources I checked before writing this reply. That is quite a bit, though only about .6 what we saw after the ice age (380+ feet).

So we really don't want to warm things up enough to do that - otherwise we'd have to say goodbye to Disneyland, MGM studios, Sea World, the Statue of Liberty, Ocean City, The Baltimore Harbor, LA, and a whole host of other even more important places

Jim

Would L.A really be that big of a loss?

[seer]

A bit over a foot. It's going up by a bit more than an inch a decade at the moment, and accelerating.

But Jim's prediction was 230 feet!

That's not the opposite of what happened. Fewer have made landfall in the US, but hurricanes have changed. We're not seeing an increase in numbers (i can go into detail on this if you'd like), but we are seeing an increase of the category 4 and 5 storms.

Really, I was speaking of Atlantic storms. There has been no increase in frequency or intensity. Where are all these Cat 4 and 5s in the last 12 years?

Nuisance flooding is caused by a mix of local sinking of the ground, and climate driven sea level rise. And it's happening much more often, as that table shows. But the magnitude of the increase varies from place to place. Wilmington, NC has seen a 40-fold increase; Providence RI has seen none. So you may just happen to be going to a place where the difference isn't as pronounced.

Right and RI is where I go. So not all sea levels will rise, and my personal observation was correct.

[seer]

Here you go sir. The answer is almost 8 inches, about 0.6 feet.

According to Lurch, they have not risen at all where I live. But Jim's prediction said they will rise 230 feet! Scare tactics?

[TheLurch]

According to Lurch, they have not risen at all where I live. But Jim's prediction said they will rise 230 feet! Scare tactics?

Read what he said more carefully - it was "if all of Greenland and Antarctica melt." It's not a prediction or scare tactics; it's math.

[Bill the Cat]

Read what he said more carefully - it was "if all of Greenland and Antarctica melt." It's not a prediction or scare tactics; it's math.

Have they all melted before?

[TheLurch]

Really, I was speaking of Atlantic storms. There has been no increase in frequency or intensity. Where are all these Cat 4 and 5s in the last 12 years?

Out at sea, where you pay no attention to them. Or striking a Caribbean island that you don't pay attention to.

[TheLurch]

Have they all melted before?

Not in many millions of years; possibly not since the PETM. But several interglacial periods have been longer or warmer than the current one due to higher CO2 levels or different orbital forcings, and sea levels were dozens of feet higher. That clearly doesn't mean they've all melted then, just that a lot more than has currently melted can if the temperature goes up slightly and stays there for a while. And by slightly, i mean "less than it will rise by the end of the century if we don't do something about emissions."

To put this in perspective, most of Florida is built on top of former coral reefs.

[seer]

Out at sea, where you pay no attention to them. Or striking a Caribbean island that you don't pay attention to.

I watch them all, so how many Cat 4s or 5s in the last 12 years?

[Sea of red]

Have they all melted before?

Yeah, during the Paleogene period, forty million years ago - not a good benchmark to shoot for.

The Laurentide Ice Sheet was the last major ice sheet collapse during our last glacial maximum. It covered all of Canada and many parts of the Northern US, and it was about 2.5 to 3.0 miles thick. It last collapsed after changes in the Earths orbit warmed global temperatures to a point that the ice sheet could not be sustained - see my previous post on the Milankovitch cycles.

[seer]

Read what he said more carefully - it was "if all of Greenland and Antarctica melt." It's not a prediction or scare tactics; it's math.

And do we predict that all that ice will melt?