97% Scientist Consensus: global warming is man-made

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kurt_w
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Re: 97% Scientist Consensus: global warming is man-made

Postby kurt_w » Sun May 18, 2014 11:19 am

Regarding the West Antarctic Ice Sheet (WAIS), let's see if we can untangle Sandi's mess:

Sandi wrote:perhaps it is the natural course of things because the land is downhill


Actually, in the case of WAIS the ice is generally flowing uphill not downhill. The mass of the ice sheet has depressed the land in West Antarctica far below sea level.

Ice in a glacier or ice sheet does not necessarily flow downhill. It flows down a pressure gradient. For a small alpine glacier this will mostly be "downhill". For a large ice sheet like WAIS, the pressure gradient is outward not downhill.

Sandi wrote: and because there are no topographic obstacles to prevent it from flowing into the ocean it is irreversible. The ‘irreversible’ part of the scare line is a good chuckle. How do you ‘reverse’ the progress of a glacier?


You don't understand the difference between the ice and the glacier.

The ice always flows in one direction, and doesn't reverse. But the terminus of the glacier can advance, retreat, or be stable, depending on the glacier's mass balance.

A glacier or ice sheet gains mass in its zone of accumulation and loses mass in its zone of ablation. If WAIS gains mass faster in its accumulation zone than it loses mass in its ablation zone, then its outlet glaciers will advance. Contrariwise, if accumulation can't keep up with ablation, then its outlet glaciers will retreat.

So, to answer your question, Sandi, you "reverse the progress of a glacier" by changing the climate such that it shifts towards a negative mass balance. Ablation outpaces accumulation, the glacier's equilibrium line and terminus retreat, and if this keeps up long enough the glacier disappears.

The situation with WAIS is that (relatively) warmer ocean water eats away at its outlet glaciers, causing their grounding lines to retreat. Because WAIS is sitting in a bowl below sea level, as the grounding lines retreat, ocean water will flow inward and downward, continuing to ablate mass from the fronts of the glaciers. As the outlet glaciers retreat inward they also steepen, which leads to more instability.

And yes, scientists have been talking about this possibility for a long time. So?

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Re: 97% Scientist Consensus: global warming is man-made

Postby Sandi » Sun May 18, 2014 11:38 am

Well. You might be right on some, or most of that Kurt. However that is of little consequence. What matters is that the ice in question has been disappearing for some 20,000 year. To make a connection between that and AGW is ludicrous.

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Re: 97% Scientist Consensus: global warming is man-made

Postby rabble » Sun May 18, 2014 11:42 am

Sandi wrote:Well. You might be right on some, or most of that Kurt. However that is of little consequence. What matters is that the ice in question has been disappearing for some 20,000 year. To make a connection between that and AGW is ludicrous.

Wow. Science!

I've got to go to my friend google to research this twenty thousand years of shrinkage since Sandi is so scientific she didn't post any corroboration. Because, science!

Oh, wait. Here's something.

Hm. I can't find the part where the ice "has been disappearing for some 20,000 year." Sandi, could you help out the wiki people and edit that page? I'm sure you've got the numbers and data handy, while I would have to keep googling for it.

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Re: 97% Scientist Consensus: global warming is man-made

Postby Sandi » Sun May 18, 2014 12:37 pm

Rabble, discourse is fine, but please: Try to have something to say, other than to just hear (see) yourself talk.

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Re: 97% Scientist Consensus: global warming is man-made

Postby kurt_w » Sun May 18, 2014 2:18 pm

Sandi wrote:Well. You might be right on some, or most of that Kurt. However that is of little consequence. What matters is that the ice in question has been disappearing for some 20,000 year. To make a connection between that and AGW is ludicrous.

You're making the same logical fallacy that Lord Haw-Haw did a few pages back in this thread.

The fact that the climate warmed from natural causes in the past does not somehow prove that the climate won't warm from unnatural causes now and in the future.

Warming at the end of the last glacial cycle caused the WAIS to recede. More warming over the next century and beyond will cause the WAIS to recede further, ultimately raising sea level by an additional six meters on top of the other sources of sea level rise.

If you want to make a connection between what happened at the end of the last glacial maximum, 20000 years ago, and what's happening now ... then the "connection" is that past events show that warming of the seas around Antarctica will cause the WAIS to shrink and sea level to rise.

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Re: 97% Scientist Consensus: global warming is man-made

Postby Sandi » Sun May 18, 2014 2:34 pm

You're making the same logical fallacy that Lord Haw-Haw did a few pages back in this thread.

The fact that the climate warmed from natural causes in the past does not somehow prove that the climate won't warm from unnatural causes now and in the future.


Please knock it off with the straw-man crap.

Climate warms from both natural and human causes. I have always believed that. With either, or both the WAIS has been disappearing for tens of thousands of years.

Your argument has nothing to do with previous discussion here.

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Re: 97% Scientist Consensus: global warming is man-made

Postby kurt_w » Sun May 18, 2014 2:47 pm

Sandi, you twice brought up the 20,000-year-old deglacial climate change (once just up-thread, and once with your "caveman" remark on the previous page).

That suggests that you think that the existence of natural climate change in the past is somehow relevant to the topic of anthropogenic climate change in the future.

Now, if you meant to say that the loss of ice from WAIS in response to warming 20,000 years ago does provide evidence to support the idea that anthropogenic warming could lead to a further massive loss of ice from WAIS in the future ... then I would agree.

But I'm guessing that's not what you meant, since when you brought up the 20,000-years-ago thing you specifically said that any connection to modern warming would be "ludicrous".

You're the one who made that connection. If you don't like my attempts to guess your reasoning, go ahead and explain why you brought it up.

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Re: 97% Scientist Consensus: global warming is man-made

Postby Sandi » Sun May 18, 2014 3:50 pm

kurt_w wrote:Sandi, you twice brought up the 20,000-year-old deglacial climate change (once just up-thread, and once with your "caveman" remark on the previous page).

That suggests that you think that the existence of natural climate change in the past is somehow relevant to the topic of anthropogenic climate change in the future.


All climate change: past, present and future are relevant. Both natural and anthropogenic climate change are always relevant to ANY discussion on climate. Period.

I know you would like to remove natural variability from all GW discussions, but it doesn't work that way. Both affect total temperature, so you can't just pick one.

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Re: 97% Scientist Consensus: global warming is man-made

Postby kurt_w » Sun May 18, 2014 4:06 pm

OK, so when you wrote

Sandi wrote:What matters is that the ice in question has been disappearing for some 20,000 year. To make a connection between that and AGW is ludicrous.


Who was making that "ludicrous" connection?

Frankly, as far as I can tell you're just doing a lot of arm-waving, with no actual point. You wanted to say something cutting about the recent news vis-a-vis WAIS but you can't figure out anything to say. So you just keep posting vague bluster.

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Re: 97% Scientist Consensus: global warming is man-made

Postby Sandi » Sun May 18, 2014 4:23 pm

Frankly, as far as I can tell you're just doing a lot of arm-waving, with no actual point. You wanted to say something cutting about the recent news vis-a-vis WAIS but you can't figure out anything to say. So you just keep posting vague bluster.


No, I didn't care whether it was cutting or not. Just that the point about WAIS was old news. Yes human contribution to CO2 may have had some affect, but the WAIS disappearing certainly is not dependent on human CO2 contributions. That point is valid.

You know very well that was my point, but rather than discuss it in a civil way, you attempt to discredit anything I post.

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Re: 97% Scientist Consensus: global warming is man-made

Postby kurt_w » Sun May 18, 2014 6:40 pm

When you post silly nonsense about "caveman farts" it doesn't actually require any work from anyone else to discredit you. You do it to yourself.

I am always happy to discuss the relationship between natural and anthropogenic climate forcings. I've done so many times in this thread already. For example, you might start with the series of posts in the middle of page 100.

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Re: 97% Scientist Consensus: global warming is man-made

Postby rabble » Sun May 18, 2014 7:27 pm

So...

Sandi says the ice "has been disappearing for some 20,000 year."

I said the wikipedia page on "the ice" doesn't say anything about that, and she should fix the page. I also mention that she didn't post any corroboration for her claim.

What do I get in response?
Sandi wrote:Rabble, discourse is fine, but please: Try to have something to say, other than to just hear (see) yourself talk.


Okay, so now I'll just ask straight out.

Who, besides you, says the ice "has been disappearing for some 20,000 years?"

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Re: 97% Scientist Consensus: global warming is man-made

Postby Sandi » Sun May 18, 2014 8:17 pm

rabble wrote:So...

Sandi says the ice "has been disappearing for some 20,000 year."

I said the wikipedia page on "the ice" doesn't say anything about that, and she should fix the page. I also mention that she didn't post any corroboration for her claim.

What do I get in response?
Sandi wrote:Rabble, discourse is fine, but please: Try to have something to say, other than to just hear (see) yourself talk.


Okay, so now I'll just ask straight out.

Who, besides you, says the ice "has been disappearing for some 20,000 years?"


Jeez rabble, that the WAIS started melting at the end of the last ice glaciation isn't in contention by alarmists, skeptics or any one else ( except apparently you ). Any disagreement is/was withing a couple millennia.

Nor is Kurt disputing it. If you are going to post, at least get a bit of background on the subject first.

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Re: 97% Scientist Consensus: global warming is man-made

Postby kurt_w » Sun May 18, 2014 8:22 pm

Rabble, Sandi happens to be right about the plain fact that the ice sheet has retreated in the past. It's Sandi's interpretation of this fact that's the problem.

It's true that the ice sheet has been retreating since the last glacial maximum (call it 20,000 years ... Close enough). There are a lot of papers that discuss this, and sometime when I'm not trying to post from a #%^} ipad I can give some links. Or someone can go to scholar.google.com and type in "wais antarctica holocene" and it should bring up a bunch of relevant papers.

There may be some dispute about how continuous that retreat has been; in some areas its seems to have been mostly prior to 10,000 years ago.

There's also evidence that during some previous interglacials, WAIS may have shrunk a lot, and added several meters to sea level.

So WAIS is clearly pretty unstable. It's possible, though by no means certain, that even without human intervention it would keep shrinking, particularly if this interglacial turns out to be like MIS11 and lasts an unusually long time.

But all the fossil carbon we're burning will accelerate that process, shortening the timeframe and increasing the total amount of ice lost and the amount of sea level rise.

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Re: 97% Scientist Consensus: global warming is man-made

Postby kurt_w » Sun May 18, 2014 8:40 pm

Sandi wrote:If you are going to post, at least get a bit of background on the subject first.

Hilarously, monumentally ironic.


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