Nasa Arctic Ice "GONE" By 2013

[InfiniteNow]

Originally Posted by C1ay

Take a look at this for an idea of man's contribution to the problem...

C1ay, there are many sources I'd trust far more than "mysite.verizon.net/mhieb...." for information on anthropgenic contributions.

[freeztar]

Originally Posted by C1ay

Considering how fast the Earth has warmed during past ice ages I wonder why the current rate would be unexpected....

Are you referring to the graph at the bottom of that page? If so, then I'd like to point out that the Y-axis is undefined (or at a minimum, vaguely defined by period). How can we determine the rate from this graph? Are you referring to something else?

[C1ay]

Originally Posted by freeztar

Are you referring to the graph at the bottom of that page? If so, then I'd like to point out that the Y-axis is undefined (or at a minimum, vaguely defined by period). How can we determine the rate from this graph?

Periods are well defined on the Geologic Time-Scale...

[freeztar]

Originally Posted by C1ay

Periods are well defined on the Geologic Time-Scale...

I'm well aware of this, but the curves on the graph are not well defined. How can we quantify the rate from that graph? Did the "switch" happen over a period of 500 years, 5000 years, or 500,000 years?
It's not clear from the graph.

[C1ay]

Look at the dip in the average global temperature that occurred around the middle of the Ordovician period that recovered back to the maximum by the first quarter of the Silurian period.

The Ordovician period spanned from 488 - 444 Mya and the Silurian from 444 - 416 Mya. By this it looks like it was approximately 29 Mya. There was an impact at Jämtland, central Sweden dated at approximately 455 Mya that could explain the sudden drop in temperature.

More importantly though you should notice that we just had an ice age in the Pleistocene period that brought the average global temperature down to 12°C and the planet is still in a warming phase from that. The Earth Policy Institute reports the average global temperature in 2007 was 14.73°C, still lower than the 17° average of the last 2 billion years. Notice also that each time the Earth has dropped down in global average temperature, because of an impact, volcanic eruption or other atmospheric event, it rebounds to around 22°C. Judging from the history of the planet we are headed back to that average.

[freeztar]

Originally Posted by C1ay

Look at the dip in the average global temperature that occurred around the middle of the Ordovician period that recovered back to the maximum by the first quarter of the Silurian period.

The Ordovician period spanned from 488 - 444 Mya and the Silurian from 444 - 416 Mya. By this it looks like it was approximately 29 Mya. There was an impact at Jämtland, central Sweden dated at approximately 455 Mya that could explain the sudden drop in temperature.

More importantly though you should notice that we just had an ice age in the Pleistocene period that brought the average global temperature down to 12°C and the planet is still in a warming phase from that. The Earth Policy Institute reports the average global temperature in 2007 was 14.73°C, still lower than the 17° average of the last 2 billion years. Notice also that each time the Earth has dropped down in global average temperature, because of an impact, volcanic eruption or other atmospheric event, it rebounds to around 22°C. Judging from the history of the planet we are headed back to that average.

Ok, I see what you are saying, C1ay, but 29 Mya is a VERY long time compared to what we are able to record "real-time" in a few generations.

Likewise, an average temp of 17 degrees over the last 2 Bil. years is hardly a metric with which to judge climate variability over a timespan of 150 years. Recent trends have a much higher temperature *increase rate* than has been seen in paleoclimatic records as far as I'm aware of. (not to discount solar variability and Milankovitch cycles)

Does anyone know of any data related to the prehistoric rate of ice cap disappearance? If so, this might help fill the gaps.

[Chris C]

there is no ice age termination over the ice core record involving a 0.8 C rise in 100 years or so . D-O events are the only thing comparable in rate, but not like today in terms of global scale effects. The rate of change is consideraly rapid on a global and decadal scale, and Milankovitch cycles operate on thousand-of-year timescales, while CO2 and methane feedbacks from warmer temperatures in the glacial-interglacial cycles take hundreds of years as well.

[Chris C]

Originally Posted by freeztar

Ok, I see what you are saying, C1ay, but 29 Mya is a VERY long time compared to what we are able to record "real-time" in a few generations.

Likewise, an average temp of 17 degrees over the last 2 Bil. years is hardly a metric with which to judge climate variability over a timespan of 150 years. Recent trends have a much higher temperature *increase rate* than has been seen in paleoclimatic records as far as I'm aware of. (not to discount solar variability and Milankovitch cycles)

Does anyone know of any data related to the prehistoric rate of ice cap disappearance? If so, this might help fill the gaps.

You are correct. I'm not very familiar with climates before the ice core record, but neither do the paleo records have time resolution of <100 years. Plate tectonics and the evolution of the air and sea (like plants and cyanobacteria giving oxygen) take a very long time to operate. You need landmass at the poles for glacial periods. I do not know of any time where ice melted at the poles on a decadal to century timescale, but if it happend it must have involved a clear external forcing on the climate system which had an abrupt effect. The glacial to interglacial cycles over the ice core record are fairly clearly slower than today, with much higher CO2 levels today as well.

[cyclonebuster]

Originally Posted by freeztar

Are you referring to the graph at the bottom of that page? If so, then I'd like to point out that the Y-axis is undefined (or at a minimum, vaguely defined by period). How can we determine the rate from this graph? Are you referring to something else?

Scary thought when looking at that graph. Modern man only exists in the very top portion of (TODAY) when the climate is cool. Perhaps, when the climate warms up more like in the past we fail to exist at all.

[C1ay]

Originally Posted by freeztar

Likewise, an average temp of 17 degrees over the last 2 Bil. years is hardly a metric with which to judge climate variability over a timespan of 150 years. Recent trends have a much higher temperature *increase rate* than has been seen in paleoclimatic records as far as I'm aware of. (not to discount solar variability and Milankovitch cycles)

I think we can see that natural warming cycles are unpredictable, sometimes they are rapid and others are slow. We are facing a warmer future either way and we should adapt. There's nothing wrong with trying to reduce the pollution we create that contributes but it's not going to stop the Earth from warming up.