quote:

Originally posted by JL(SFC58,AFCB):
Let me get this right. If temperatures go up, it is due to global warming. If temperatures go down it is due to global warming. Does it strike you that global warming has now become exempt from the rules by which there must be some conceivable data to disprove?

No it strikes me that you don't understand. "If temperatures go up, it is due to global warming. If temperatures go down it is due to global warming." is an incorrect summary. Keep trying though, you'll get it one day I'm sure.

I have just thought of a simple analogy that might help JL(SFC58,AFCB) and others understand how local temperatures might fall even when there is global warming occurring. The analogy is the stock exchange. This goes up and down on a daily bases, yet the overall trend is upward. But on a day when it goes up, so some stock prices might fall. On a day that it goes up, the loses and gains are added together to give a net gain.

Global warming is just the same. Temperatures go up and down day by day, year by year at each monitoring point. But when all the points are added together, the trend is upward.

ApeMan

My point was very simple. Increased ice was being taken as a sign that there is global warming. What, then, would be taken as a sign of no global warming?

quote:

Originally posted by JL(SFC58,AFCB):
ApeMan

My point was very simple. Increased ice was being taken as a sign that there is global warming. What, then, would be taken as a sign of no global warming?

Increased ice in Antarctica was predicted as a consequence of global warming. It hasn't occurred though: the ice is shrinking as the edges are flowing into the sea faster than the increased precipitation caused by warmer oceans is building up extra ice in the interior.

A sign of no global warming would be a flat or falling annual mean global temperature trend.

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Originally posted by Ape Man:
Increased ice in Antarctica was predicted as a consequence of global warming. It hasn't occurred though: the ice is shrinking as the edges are flowing into the sea faster than the increased precipitation caused by warmer oceans is building up extra ice in the interior.

A sign of no global warming would be a flat or falling annual mean global temperature trend.

So Global Warming has failed the increased ice test? Interesting?

How long must the flat or falling trend continue? Is seven years enough?

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than the increased precipitation caused by warmer oceans is building up extra ice in the interior

So why are the warming oceans cooling?

http://www.pmel.noaa.gov/people/lyman/Pdf/heat_2006.pdf

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Originally posted by JL(SFC58,AFCB):
So Global Warming has failed the increased ice test? Interesting?

Not really. The interior ice is increasing. The ice around the edges is being lost faster than expected though: that is the bit of the models that has failed.

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How long must the flat or falling trend continue? Is seven years enough?

The trend is typically calculated on an eleven year rolling mean (not sure why eleven years is used), so no seven years is too short a time.

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Originally posted by Son of Mulder:

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than the increased precipitation caused by warmer oceans is building up extra ice in the interior

So why are the warming oceans cooling?

The ocean surface has cooled over the last 3 years. The cooling is a tiny fraction of the warming that has occurred over the last 50 years. The oceans are still far warmer now than they were in the 80s. Come back in ten years and we might have enough data to know if it is a cooling blip or if they are in long term cooling mode.

‘So why are the warming oceans cooling?’
http://www.pmel.noaa.gov/people/lyman/Pdf/heat_2006.pdf

But they also report that sea levels continue to rise due to melting ice in Antarctica and Greenland.

Page 6. “Estimates of total sea level [Leuliette et al., 2004; http://sealevel.colorado.edu/, however, show continued sea-level rise during the past 3 years. This suggests that other contributions to sea level rise, such as melting of land-bound ice, have accelerated. This inference is consistent with recent estimates of ice mass loss in Antarctica [Velicogna and Wahr, 2006] and accelerating ice mass loss on Greenland [Rignot et al., 2006].”

Humm, what happens when you add a lot of freshly melted ice water to an ocean, could that cool it? Just a thought.

For sea levels: <Scroll down page:>
http://sealevel.colorado.edu/

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Humm, what happens when you add a lot of freshly melted ice water to an ocean, could that cool it? Just a thought.

But melt water sinks because it's denser, so how would that sffect surface water temperatures?

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Originally posted by Son of Mulder:

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Humm, what happens when you add a lot of freshly melted ice water to an ocean, could that cool it? Just a thought.

But melt water sinks because it's denser, so how would that sffect surface water temperatures?

The whole panic (which is looking unfounded at the moment) over the collapse of the Gulf Stream is due to the fact that cold fresh water can be less dense than warm salt water and so a melting Arctic would stop sinking which would shut down the N. Atlantic Conveyor, which feeds the Gulf Stream. So there is some logic in the idea that fresh melt water might not sink and thus it would cool the surface waters. But the observations do not appear to support this idea.

So what are the theories for cooling blip vs longer term ocean cooling?

But melt water sinks because it's denser, so how would that sffect surface water temperatures?

True, but convection will transfer heat energy producing an overall cooling. The oceans aren’t static; there will be convection currents.

As I said, it’s just a thought. The researchers didn’t have a specific answer either. But it’s not evidence of global cooling, just an interesting phenomenon at present.

Just to note also that the pacific cooled by 1.5 degrees between around 450 AD and 1450 AD (The MWP occurred during that time). Temperatures then rose sharply by 1.5 degrees in around 1450 and remained so until the 20th century. (The LIA occurred during that time). It’s still a puzzle why?

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Originally posted by Son of Mulder:
So what are the theories for cooling blip vs longer term ocean cooling?

Assuming its a blip, then the "theory" is that the oceans act a bit like the atmosphere, ie they are a chaos system that does weird shit at times. It's a bit like us having a warm winter followed by the nice steady warming of spring with a sudden plunge in the temperature this week.

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Assuming its a blip, then the "theory" is that the oceans act a bit like the atmosphere, ie they are a chaos system that does weird

And therein lies one of my key scientific concerns about the hypothesis that we are going to get significant and dangerous climate change.

Chaos makes it unpredictable and it may get warmer, it may get colder or it may still just oscillate about , blip follows blip follows blip. So what's new?

In reply to comments about the Gulf Stream and the suggestion that it might shut off:

There is certainly evidence that on glacial/interglacial timescales the Gulf Stream either shut down or was, more likely, reduced in scale. The last time that it is proposed that it siginificantly changed is about 8200 years ago when a giant freshwater lake (from glacial meltwater) broke through its barrier and flowed into the North Atlantic. The science is not certain sadly but the calculations of the amount of freshwater are HUGE! In the world today there is almost no way of generating that much fresh water and dumping it all at once into the North Atlantic. This means that it is highly unlikely to shut down but it may slow down due to increased freshwater input e.g. from Greenland maybe.

I would ask though - who caused the 'panic' over the possibility? I would say the media - it is always easier to sell dramatic stories using the most extreme statements from scientific literature out of context than explain the result as part of the larger study. In part the scientific community must take responsibility for this but it also requires more responsible, moderate reporting.

Leave drama to Hollywood - I do agree that 'The Day After Tomorrow' would have been much more dull if it had taken place over decades (and without the escaped wolves!). But please make it clear that it is drama not science!!

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Originally posted by julieef:
I would ask though - who caused the 'panic' over the possibility? I would say the media...

I agree. I apologise if I implied the scientists were to blame for the panic.

Just to help those who are wondering about the relative density of the cold melt water and the sea water, at 20C the density of sea water is 1025kg/cu. m while that of fresh water is 998 kg/cu. m The cubic expansivity of water is 0.21 e-3 per K so for sea water to be less dense than fresh it would have to be 120 degrees hotter!

I think its safe to assume that the fresh will be on top.