Arctic Ice Discussion

[Gray-Wolf]

Ahh yes, never a ramper for ice melt

I seem to remember you predicted that last year as well, and the year before that, one day you are bound to be right.

Glad to see you keeping with 'the trend' NNW!

I'd take issue at being a 'ramper' for melt?

I've been correct in my observations of melt Esp. over the 'collapse and spread years.

I've been right in my Fram and Nares observations of winter ice export.

This year will show my concerns over NW Passage (and it's feed channels) as another 'Exit' From the Arctic are founded.

The 'mix out of the halocline' was another great concern for me and now both the oceanographers and the Catlin team are showing us that this has now taken place across large expanses of the basin.

To me it seemed no more than 'logical' that the Paleocrystic could not survive long once 07' had opened up so much water to 'normal oceanic processes'? no 'ramp' there just an observation of the facts as the process was ongoing.I was ,of course, very glad to have had Prof Barbers team there to witness it in S.Beaufort though (there are those on here that think I just make up half I post???) . But 'Ramper'? ?,no!, Worrier , Yes and as such the prospect of being where we are 'Worries' me greatly.

To me It is akin to watching a train wreck in slow mo. whilst all around go on without a care.

The partial loss of the permafrost will introduce more GHG's into the atmosphere than we have over the past 70yrs and if we feel that we have done wrong in upping GHG levels to todays ppm's then what of the ppm's going up by another 2/3's of todays levels (into the 750's?) over a 7 or 8 year period??? To me that would be a 'worry'.

Yup ,a worrier for sure (but do I have cause to?), a Ramper? Nope ,not me Sir.

EDIT: Sorry NNW , lost your question! The 'complete melt out phase of the melt season (to me) is when the ice that is thin enough melts out completely in mid Aug onwards. With so much 'uniform' thin ice and 'uniform' weather across the basin this year may see a rapid expansion of open water come mid to late Aug.

Though no-one has called it yet I'm sure the 'perfect storm' cards will be played if we do exceed the 07' min extent? As it is I feel that the majority of the losses will be in the Basin (not quite a 'Di-pole' set up but one that helps spin a central gyre around the pole?).

Edited July 12, 2011 by Gray-Wolf

[bobbydog]

this is a subject i'm obviously aware of but not familiar with. could anyone explain, in laymans terms, what the consequences of a total melt would be?

[quest4peace]

Hi Peeps erm i am a total novice i must confess, but what do the more learned people than i think of this?

Credit to this site: http://www.johnstons...waterworld.html

"What If All the Ice Melts?" Myths and Realities

by Wm. Robert Johnston

last updated 29 December 2005

"If we keep using cars, the ice caps will melt and we'll all drown!" This is a myth, just as false as fearing the Sun will die as a result of using solar power. However, as often as I hear it--particularly from people who should know better--I thought I would address it here. First, here is a summary of the facts:

Despite what you may have been told, it has NOT been proven that human-caused global warming is occurring, and in fact there is substantial reason to reject such claims.The best explanation for the evidence is that whatever global warming trend exists is mostly the result of natural influences like variations in the climate system and variations in solar radiation.The suggestions that human activities will cause significant changes in global temperature and sea level in the next century are flawed predictions which haven't been confirmed by observations.The solutions to this apparently non-existent problem proposed by environmentalists would not have a significant effect on climate, but they would cause a significant amount of human suffering.Based on what we know now, in the next 100 years a rise in sea level of 0.1 meters (4 inches) would not be surprising; those predicting changes of 0.5-2 meters (1.5-7 feet) are using flawed models.If all the icecaps in the world were to melt, sea level would rise about 60-75 meters (200-250 feet). This could not result from modern human activities, and from any realistic cause would take thousands of years to occur. I have discussed the first four points (which are non-trivial and deserve extended discussion) in Global warming, Some scientific data on global climate change, and "Facts disprove warnings about global warming", and the fifth point in Facts and figures on sea level rise. I will mostly address the last point--not just to dispel the notion that we need worry, but also because it is a valid and interesting thing to be curious about.

I. The world's ice

Currently the Earth has permanent ice in the icecaps of Antarctica and Greenland, plus much smaller permanent glaciers in various mountain regions of the world. This ice is "permanent", however, only over the short timespan of modern human civilization. Additionally there are two large ice sheets floating in seas off Antarctica, plus floating pack ice in the Arctic Ocean and surrounding Antarctica. Geological evidence indicates very clearly that at times in the Earth's past icecaps were much larger in extent--and alternately, at other times icecaps were virtually nonexistent.

Currently there are about 30,000,000 cubic kilometers of ice in the world's icecaps and glaciers. This volume of ice is fairly well measured (within 5-15%) by surveying the top of the icecaps with methods like radar and laser altimetry, locating the bottom of the ice with methods like seismic soundings, and calculating the difference. A breakdown is as follows:

Grounded ice is ice resting on the ground rather than floating. The melting of floating ice will not change sea level: the mass of this ice is equal to that of the water it displaces (watch the water level in a cup of floating ice cubes as they melt). For comparison, globally ice (both grounded and floating) represents about 2% of the world's water, with about 1,350,000,000 km³ of water in the oceans.

During the last Ice Age the maximum extent of glaciation was around 16,000 B.C. At that time large ice sheets covered all of Canada, much of the American midwest and northeast, all of Scandinavia and some surrounding regions of Eurasia. The total volume of ice then was perhaps 80,000,000 cubic kilometers, or between two and three times as much as today. Correspondingly, world sea level was about 120 meters lower [6,30].

II. Why melting is not a threat

While today's balance between the icecaps and global sea level has been relatively steady since about 1000 B.C., it would be careless to assume that this is the Earth's natural state and that it should always be this way. What could happen to climate naturally in the next few thousand years? If the Earth continued to warm and break from ice age conditions, some of the remaining ice caps could melt. On the other hand, climate might swing back into another ice age. (In fact, some of the environmentalists now worried about global warming were worried about another ice age in the 1960s and 1970s.)

In either case, such a change in climate would take thousands of years to accomplish. Note that it has taken 18,000 years to melt 60% of the ice from the last ice age. The remaining ice is almost entirely at the north and south poles and is isolated from warmer weather. To melt the ice of Greenland and Antarctica would take thousands of years under any realistic change in climate. In the case of the East Antarctic Ice Sheet, which accounts for 80% of the Earth's current ice, Sudgen argues that it existed for 14,000,000 years, through wide ranges in global climate. The IPCC 2001 report states "Thresholds for disintegration of the East Antarctic ice sheet by surface melting involve warmings above 20° C... In that case, the ice sheet would decay over a period of at least 10,000 years." [31] The IPCC is the United Nations' scientific committee on climate change; its members tend to be the minority that predicts global warming and its statements tend to be exaggerated by administrators before release. Given that the IPCC tends to exaggerate the potential for sea level rise, it is clear that no scientists on either side of the scientific debate on global warming fear the melting of the bulk of Antarctica's ice. Consider also this abstract of an article by Jacobs contrasting scientific and popular understanding:

A common public perception is that global warming will accelerate the melting of polar ice sheets, causing sea level to rise. A common scientific position is that the volume of grounded Antarctic ice is slowly growing, and will damp future sea-level rise. At present, studies supporting recent shrinkage or growth depend on limited measurements that are subject to high temporal and regional variability, and it is too early to say how the Antarctic ice sheet will behave in a warmer world. [32]

This statement alludes to the significant point that the Antarctic ice cap appears to currently be growing rather than shrinking. In fact, were the climate to warm significantly in the next few centuries (not a certain future, but supposing it happened), current models suggest that Antarctica would gain ice, with increased snowfall more than offsetting increased melting.

How much concern should we have about the 20% of world ice outside the East Antarctic Ice Sheet? Some sources have recently discussed the "possible collapse" of the West Antarctic Ice Sheet (WAIS). It is suggested that this sheet (about 10% of Antarctic ice) could melt in the "near term" (a usefully vague phrase) and raise sea level 5 to 6 meters. Current understanding is that the WAIS has been melting for the last 10,000 years, and that its current behavior is a function of past, not current climate. [23] The abstract of an article by Alley and Whillans addresses this:

The portion of the West Antarctic ice sheet that flows into the Ross Sea is thinning in some places and thickening in others. These changes are not caused by any current climatic change, but by the combination of a delayed response to the end of the last global glacial cycle and an internal instability. The near-future impact of the ice sheet on global sea level is largely due to processes internal to the movement of the ice sheet, and not so much to the threat of a possible greenhouse warming. Thus the near-term future of the ice sheet is already determined. However, too little of the ice sheet has been surveyed to predict its overall future behavior. [34]

Similarly, recent stories have periodically appeared concerning the potential receding of the Greenland ice cap. Two points may be made regarding current understanding here. First, there is considerable disagreement as to the current rate of net ice cap loss--or even if there is net loss versus net gain. Second, even with temperature increases far greater than the dubious predictions of the IPCC, models indicate that Greenland's ice cap would take 2,000 to 10,000 years to disappear.

Some discussion of the concerns about near term sea level rise may be found in Facts and figures on sea level rise. The predictions that have been made for ice cap melting in the next century rely mostly on melting of glaciers in mountain regions, not melting of the polar ice caps. Even the pessimistic models cited by the IPCC tend to predict an increase in the volume of the Antarctic ice cap with warmer temperatures due to increased snowfalls. In general temperature changes of a few degrees do not seem to be sufficient to begin to melt the polar ice caps, particularly the Antarctic ice cap.

III. Imagining the world without ice caps

As long as we understand that the polar ice caps are not going to melt in the foreseeable future, we can proceed to imagine what the world would be like if they did melt.

Using the ice volume figures from above it is straightforward to estimate the effect on sea level were all this ice melted. Melting the 29,300,000 km³ of grounded ice would produce 26,100,000 km³ of water. Note that melting of floating ice has no effect on sea level. Also, about 2,100,000 km³ of the grounded ice in Antarctica is below sea level [19] and would be replaced by water. Thus, the net addition to the world's oceans would be about 24,000,000 km³ of water spread over the 361,000,000 km² area of the world's oceans, giving a depth of 67 meters. The new ocean area would be slightly larger, of course, since some areas now land would be covered with water. The final result would be around 66 meters (current estimates range between 63 and 75 meters).

What would the Earth look like as a result? If sea level were 66 meters higher than today, the result would be as illustrated below (for the map I used below see this page):

Obviously some areas are affected more than others. Some larger areas now underwater are the southeastern United States, part of the Amazon River basin, northern Europe, Bangladesh, parts of Siberia along the Arctic Ocean, and portions of mainland China. A large area in Australia would be below sea level, but it is not joined to the ocean and could remain dry.

Both Greenland and Antarctica, free of ice, have areas that would be below sea level. However, with the weight of this ice removed, Greenland and Antarctica would rise higher--this phenomena is called isostatic rebound. This rebound lags behind the removal of the ice (by thousands of years). Eventually, most of Greenland would probably be above sea level. However, significant portions of Antarctica would remain underwater. This is shown below in a view of the southern hemisphere:

Today the Earth has 148 million sq. km of land area, of which 16 million sq. km is covered by glaciers. A sea level rise of 66 meters would flood about 13 million sq. km of land outside Antarctica. Without polar ice, Antarctica and Greenland would be ice free, although about half of Antarctica would be under water. Thus, ice-free land would be 128 million sq. km compared to 132 million sq. km today.

As a result, in terms of total habitable land area, the Earth might have more than today. The coastal areas reclaimed by the sea would be mostly offset by now habitable areas of Greenland and Antarctica. Again, remember that such climate change would take thousands of years. Over such time scales vegetation would be restored to newly ice-free regions even without human activity. Also, vast areas which are now desert and tundra would become more fit for human habitation and agriculture.

The illustrations above do not depict any changes in vegetation. In reality, local climates would be very different in ways that are currently difficult to predict. It might be that the warmer climate would lead to generally greater precipitation (this is suggested by comparison to the last ice age, when cooler temperatures caused expansion of the Sahara). Unfortunately, current models are not reliable enough to give a confident answer.

So why wouldn't people drown? Again, a change in the Earth this dramatic would take thousands of years to effect from any realistic cause. Over generations people would migrate as the coasts changed. Consider that virtually all of the settlements in the United States were established only in last 350 years. Of course, many settlements inhabited for thousands of years would have to be abandoned to the ocean--just as many would have to be abandoned if ice age conditions returned and covered vast areas with ice sheets. But people can comfortably adjust where they live over periods of decades, far shorter than the thousands of years needed for these climate changes to naturally take place. Also, that's if they occur, and we have no evidence to indicate what would happen to climate over the next few thousand years.

IV. A final comment

For those curious as to what the Earth would be like with the ice caps melted, this report has hopefully given an illustration, along with some perspective: this sort of change cannot be affected by modern human activity even given many centuries. It is sad that some youngsters think that burning of hydrocarbons could cause the ice caps to melt and drown cities; it is criminal when teachers don't correct this nonsense. And it should tell you much of environmental groups like the Sierra Club when they use such myths to further an extremist political agenda.

© 2002-2003, 2005 by Wm. Robert Johnston.

Last modified 29 December 2005.

Return to Home. Return to Environmental Topics.

Edited July 12, 2011 by quest4peace

[songster]

The paper shows that one year dramatic melt doesn't produce a tipping point beyond which the decline to no summer ice is an inexorable tale waiting to unfold. Does it show that you get all the recovery you’ll ever get within the first two to three years? If it does then it’s playing the crystal ball trick again; saying the ice recovers to the previous level in two to three years is a valid comment but “all the recovery you’ll ever get�???? That’s not only an outrageous ‘out there’ comment but scientifically inaccurate too.

Uh, either you believe their model or you don't. You can't just believe the bits you like (rapid recovery after ice removal) and ignore the bits you don't (continued ice loss if CO2 levels stay high). "All the recovery you'll ever get" is a perfectly valid statement of what the paper predicts. You take the ice away, the level bounces back up to where it was - but no higher - and then rejoins the downward trend.

[jethro]

Uh, either you believe their model or you don't. You can't just believe the bits you like (rapid recovery after ice removal) and ignore the bits you don't (continued ice loss if CO2 levels stay high). "All the recovery you'll ever get" is a perfectly valid statement of what the paper predicts. You take the ice away, the level bounces back up to where it was - but no higher - and then rejoins the downward trend.

There is no picking and choosing on my part. I have explained the reasons why the statement is questionable and included a few climate variables which could alter their prediction. If you support their work and disagree with my summary then could you please show why the variables and new research could not possibly alter the course of a never ending spiral of declining ice.

[bobbydog]

quest4peace - thanks for finding that info, a very interesting read i'm sure the more informed members will have their opinions on it and it would be nice to hear them! i'm not sure if your post was a direct answer to my earlier question or coincidental but it did, i suppose, answer it as it read. my question was more directed to gray wolf ( but not exclusively, if anyone else can answer, thats fine) and his 'worries' about it, as to the shorter term effects of a total Arctic ice melt and how and if it would affect global weather patterns, ocean currents etc.

[quest4peace]

quest4peace - thanks for finding that info, a very interesting read i'm sure the more informed members will have their opinions on it and it would be nice to hear them! i'm not sure if your post was a direct answer to my earlier question or coincidental but it did, i suppose, answer it as it read. my question was more directed to gray wolf ( but not exclusively, if anyone else can answer, thats fine) and his 'worries' about it, as to the shorter term effects of a total Arctic ice melt and how and if it would affect global weather patterns, ocean currents etc.

Kind of both B) to you and others in general I think it might of been a bit too unspecific for the title of this thread Although it does sort of answer whether the arctic sea ice melting would have that much impact on sea levels in the greater scheme of things?

Edited July 12, 2011 by quest4peace

[jethro]

Kind of both B) to you and others in general I think it might of been a bit too unspecific for the title of this thread Although it does sort of answer whether the arctic sea ice melting would have that much impact on sea levels in the greater scheme of things?

I've got the attention span of a goldfish at this time of night so a very brief answer.....melting ice would cause sea level rises if the ice was land based - the Greenland ice cap and most of Antarctica. The Arctic ice would not cause a rise in sea level, it is a floating mass sitting on top of an ocean, ice displaces it's own volume in water so liquid or solid would make no difference.

Greenland becoming habitable with agricultural land - subject to so many variables, it's impossible to say; cultivation relies upon more than just available land - altitude, temperature range, precipitation are just a few which instantly spring to mind.

[Gray-Wolf]

Back to the ice and Arctic today!

It appears we are still on with the 'big melt' phase? The N.Pole cam (2) does show open water as well as melt ponds. The 'lead' in the mid distance has now grown a lot wider (and has a nice ice sculpture showing how the base of the ice melts out!!!) and is all Arctic Ocean. If the foreground pond melts deep enough we may see this area become unstable and fragment off into the lead.

NW Passage is breaking up the remaining ice but it will still be a while before large vessels can navigate it. Does anyone know if any ships have requested passage? I know they do for the N.Passage (like the liquid gas tankers) but know nothing of the NW Passage. Most of the talk appears to centre around this route so I'd been expecting a few 'toughened Hull' vessels to give it a punt?

[quest4peace]

Thanks for you reply Jethro I think there is still so many things in the world that we still truly don't know Yes we can confirm what is happening before our own eyes,but as for the future? Do we really have enough to go on from only 30 years of satellite imagery of the Arctic Ice It is such a tiny time span in the greater picture of things, that i think, just like people used to have scientific sureity that the earth, was the centre of the universe, and everything rotated round us. These theories were set in stone back then.

Edited July 13, 2011 by quest4peace

[noiv]

> But people can comfortably adjust where they live over periods of decades, ....

So, that's the plan: We just invite the next generations to adapt to the consequences this generation has forced, because we failed to adapt to the planet we're living on. The good news is they can't reject the invitation.

Arctic just lost 1,000,000 square kilometers of sea ice extent within 8 days during this month (IJIS). Anybody eager to see this happen in 7 days?

[Thundery wintry showers]

Looking over Jethro's posts and Songster's reply, I think there are a few points to note.

The paper does suggest that the Arctic Amplification, in itself, probably doesn't produce a tipping point, which is also a conclusion reached by quite a few other papers that I looked at in the past year. This means that if global temperature remains constant we can probably expect the Arctic sea ice to readjust to a lower equilibrium level rather than continually melting away, and a sustained recovery to follow anomalous years like 2007.

The problem is that global temperatures are expected to keep on rising, and each X rise in global temperature tends to produce 2 to 5 times X worth of warming in the Arctic due to the Arctic Amplification. Rising temperatures are strongly correlated with ice melt at the margins. I think this is the main source of the long-term downward trend and anomalies in atmospheric circulation, sea currents etc. will add variability either side of the trend line, hence the anomaly in 2007 being followed by a slight recovery, correcting the sea ice extent back towards the trend line.

[noiv]

.. The paper does suggest that the Arctic Amplification, in itself, probably doesn't produce a tipping point, which is also a conclusion reached by quite a few other papers that I looked at in the past year. This means that if global temperature remains constant we can probably expect the Arctic sea ice to readjust to a lower equilibrium level rather than continually melting away, and a sustained recovery to follow anomalous years like 2007.

The problem is that global temperatures are expected to keep on rising, and each X rise in global temperature tends to produce 2 to 5 times X worth of warming in the Arctic due to the Arctic Amplification. Rising temperatures are strongly correlated with ice melt at the margins. I think this is the main source of the long-term downward trend and anomalies in atmospheric circulation, sea currents etc. will add variability either side of the trend line, hence the anomaly in 2007 being followed by a slight recovery, correcting the sea ice extent back towards the trend line.

Saying Arctic Amplification does not produce a tipping point, does not mean there are no tipping points at all. Isn't excluding tipping points but accepting anomalies an indisputable contradiction in terms? And since when lead combined and powerful positive feedbacks to a linear trend line?

Last winter a substantial amount of thick ice escaped through Fram Strait. Now the fractured rest is drifting with ~20km per day towards Beaufort Sea where it will melt first next season. It is time to prepare forgetting about multi-year sea ice and getting comfortable with multi-week sea ice.

[Gray-Wolf]

Saying Arctic Amplification does not produce a tipping point, does not mean there are no tipping points at all. Isn't excluding tipping points but accepting anomalies an indisputable contradiction in terms? And since when lead combined and powerful positive feedbacks to a linear trend line?

Last winter a substantial amount of thick ice escaped through Fram Strait. Now the fractured rest is drifting with ~20km per day towards Beaufort Sea where it will melt first next season. It is time to prepare forgetting about multi-year sea ice and getting comfortable with multi-week sea ice.

I'd have to agree with your take on the paleocryistic noiv, multiweek will be the norm over the coming years with most ice not surviving beyond 18months (as we see today in a majority F.Y. ice pack over winter?

The old areas of the basin that used to promote thickening and over ride are now turning into export areas (Lincoln sea,S.Beaufort,Greenland sea) with the prospect of the NW Passage Deep channel adding another large exit over the late summer months (the way Nares occasionally did in the 60's and 70's).

Any Idea why IJIS is stuck on the 11th?

[paul tall]

You do realise right, that analysis of ice samples from Greenland show that some of the warm periods in the last 400,000 years show previous warm spells in the climate to be up to 5ºc warmer than today? Who do we blame for that?

Point is, IF we are warming, it's happened before, ice is going to melt, some places are going to get flooded, there's nothing we can do about it, and we can't be sure we are the cause when there are natural examples of greater warming than today. So why waste so much time worrying? What is going to happen is going to happen. If it actually happens.

Any Idea why IJIS is stuck on the 11th?

To hide the ice melt truth from you.

[Methuselah]

You do realise right, that analysis of ice samples from Greenland show that some of the warm periods in the last 400,000 years show previous warm spells in the climate to be up to 5ºc warmer than today? Who do we blame for that?

In terms of measuring the extent of the global temperature-increase brought about my manmade CO₂ (itself a fact of chemistry and physics) that statement is entirely irrelevant!

Who shall we 'blame' for the Snowball Earth epoch, then? Father Christmas???

[jethro]

Isn't the important question "have we caused the current melt, if so how much of it"?

[noiv]

> Isn't the important question "have we caused the current melt, if so how much of it"?

So, as long as the melting can not be perfectly attributed to humans there is an excuse to continue with business as usual? Does putting a habitable planet at risk by just saying "I'm not convinced" show any sign of accepting responsibility?

Weather in Tiksi, Russia today: Mostly Cloudy. High: 26 °C. Wind SW 22 km/h.

[Thundery wintry showers]

Saying Arctic Amplification does not produce a tipping point, does not mean there are no tipping points at all. Isn't excluding tipping points but accepting anomalies an indisputable contradiction in terms? And since when lead combined and powerful positive feedbacks to a linear trend line?

Last winter a substantial amount of thick ice escaped through Fram Strait. Now the fractured rest is drifting with ~20km per day towards Beaufort Sea where it will melt first next season. It is time to prepare forgetting about multi-year sea ice and getting comfortable with multi-week sea ice.

I didn't say that it doesn't, I included the term "probably", although I forgot to mention that quite a number of papers suggest that a "tipping point" is somewhat more likely to occur if we lose most of the Greenland ice sheet. This implies that there's a pretty significant likelihood of us reaching a tipping point in the Arctic the near future unless global warming over the 21st/22nd centuries turns out to be much smaller than expected. To my mind, the Greenland ice sheet is by far the bigger worry for a number of reasons.

I think the chances are that human activity has contributed to the melting of the Arctic sea ice. Most of the evidence I've seen suggests that at least half of the twentieth century warming of the mean global temperature (and probably more) has been associated with human activity, and as mentioned earlier, the Arctic Amplification means that the Arctic usually warms at a much faster rate than the global mean. There is also evidence that industrial pollution/soot/carbon deposits may have contributed to the reduced albedo over the sea ice, helping to accelerate its melting. There are also natural forcings such as atmospheric circulation and ocean currents to take into account- these probably masked the effects of global warming during the 1980s and 1990s when atmospheric circulation was often favourable for sea ice retention, and then exaggerated the effects during the 2000s when atmospheric circulation shifted the other way.

[jethro]

> Isn't the important question "have we caused the current melt, if so how much of it"?

So, as long as the melting can not be perfectly attributed to humans there is an excuse to continue with business as usual? Does putting a habitable planet at risk by just saying "I'm not convinced" show any sign of accepting responsibility?

Weather in Tiksi, Russia today: Mostly Cloudy. High: 26 °C. Wind SW 22 km/h.

But that assumes a totally irresponsible, wanton waste mentality, which to be honest, I've yet to encounter in any human being whether they believe in AGW or not. Consumption of our species depends simply on two things, need and want - need doesn't change that much, want varies depending upon disposable income. Generally speaking, belief in climate change doesn't enter into decisions when the newest, latest wide-screen tv or gadget phone comes onto the market. Attempting to make consumers feel guilty about buying new things ignores basic human behaviour (always a waste of time) and completely ignores the basics of how modern, capitalist society works - again, an utter waste of time.

Meaningful changes in CO2 emissions needs to come from the top, whether that be how our energy is generated or the development and introduction of new materials to make every product as environmentally friendly as possible; trying to lay a guilt trip on people is neither helpful to getting the message across nor making a difference to the emissions levels.

I for one am tired of the pedestal approach to this discussion, those who believe in the theory of AGW are no more morally superior than those who don't, or those who question aspects of the theory. IMO the "there is an excuse to continue with business as usual" approach to this discussion is lazy, ineffectual and fatuous.

Meanwhile, there are many folk like me who live an incredibly green lifestyle who are interested in the science of this discussion and the many loopholes and missing answers. I'm not looking for perfect attribution to humans, simply trying to understand how much is our responsibility, surely that's not too much to ask.

[noiv]

Jethro,

it looks to me you found a satisfying answer on how and why we are responsible, but I fail to understand the motivation of exploring the question of how much. Isn't that the beginning of an endless journey, which may not even end after you know the history of each single molecule of CO2? And it was not my intention to spread bad feelings. What is your reply when people unfold a plan of the next thousand years, but still struggle to live sustainable the next five minutes?

"The fraction of total ice extent made up of multiyear sea ice in March decreased from about 75% in the mid 1980s to 45% in 2011, while the proportion of the oldest ice declined from 50% of the multiyear ice pack to 10%." http://www.agu.org/p...1GL047735.shtml, published 14/07/2011.

[paul tall]

In terms of measuring the extent of the global temperature-increase brought about my manmade CO₂ (itself a fact of chemistry and physics) that statement is entirely irrelevant!

Who shall we 'blame' for the Snowball Earth epoch, then? Father Christmas???

What is your point? Nobody is to blame for snowball earth, just like nobody was to blame for warmer periods than we are now in.

Weather in Tiksi, Russia today: Mostly Cloudy. High: 26 °C. Wind SW 22 km/h.

Are you trying to illustrate a point there?

Temperatures in Verkhoyansk at 67ºN have reached 36ºC in the past and at 71ºN they have seen extremes of 31ºC. Most years Verkhoyansk will hit 30º+ and it stands to reason that most years Tiksi will have a day or two at 26º...

[noiv]

>> Weather in Tiksi, Russia today: Mostly Cloudy. High: 26 °C. Wind SW 22 km/h.

> Are you trying to illustrate a point there?

Thanks for pointing to other relevant stations, I'll make my point after I got an answer to the question: "How many trees make a forest?"

[jethro]

Jethro,

it looks to me you found a satisfying answer on how and why we are responsible, but I fail to understand the motivation of exploring the question of how much. Isn't that the beginning of an endless journey, which may not even end after you know the history of each single molecule of CO2? And it was not my intention to spread bad feelings. What is your reply when people unfold a plan of the next thousand years, but still struggle to live sustainable the next five minutes?

"The fraction of total ice extent made up of multiyear sea ice in March decreased from about 75% in the mid 1980s to 45% in 2011, while the proportion of the oldest ice declined from 50% of the multiyear ice pack to 10%." http://www.agu.org/p...1GL047735.shtml, published 14/07/2011.

I’ve been involved in this discussion in one form or anther for over 6 years now, I know why we’re considered to be responsible.

We need to know how much we’re responsible for for many reasons, saying we don’t need to know is akin to saying we know the Moon sits in the sky and that it’s a long way away but we don’t know how far away, nor do we need to know how far, it’s a pointless piece of information. Of course we need to know how much of the warming is our contribution. Off the top of my head here are a few reasons why….

Climatology is a new multi-discipline science drawing on all the other sciences, science (especially new sciences) need to progress, in order to do so the information has to be honed and finally tuned. Modern society and technology relies heavily upon science, much of that depends upon having trust in the science, a kind of mega scale version of ‘I don’t know, but I know a man who does’ – that trust that we all depend upon is earned through their expertise, knowledge and accuracy.

There is potential for melting ice to substantially rise sea levels, this rise may displace many thousands of people and lose vital agricultural land. We need to plan for this before it happens and we need to have a pretty accurate timeline in order to do so, that timeline can only be accurately drawn with a more thorough knowledge of our contribution to the warming and thus any additional warming we may still cause. The vague ranges we’ve given so far are too large for meaningful plans to be drawn up – who will commit the many trillions which will be needed if there is deemed to be no real risk or immediate risk. Conversely, how will we raise the many trillions needed at short notice if the science calculations are wrong and the seas start to rise in the near future?

Developing food crops which will better survive adverse growing conditions takes time, many do not want GM foods but there is a large drive towards them based upon the theory of AGW and the predicted need for them. If the need has been over-estimated we may not need to artificially modify crops, again conversely, we may need them a lot quicker that the horticultural world has anticipated and they may need to drastically step up production. Knowing how much we have contributed to the warming will enable a better calculation of the future based on the continuing level of emissions.

New power sources - we need more environmentally friendly means of generating energy; do we have time to explore the many options, develop new ones or do we have to press ahead with known technology even though it’s a long way from perfect. Do we have to build nuclear power stations asap in order to rid ourselves of the dirtier coal plants or do we look to alternative means which could come on-line at a later date? What about the proposed off-shore wind stations, we know they’re far from effective but there’s a headlong rush to build them, could we take more time to refine that technology if we knew we’d only contributed a tiny percentage of the warming? We’re running out of fossil fuel but the drive to switch to alternatives as quickly as possible is driven by the seemed urgent need to curb emissions, remove or tone down that urgent need and we may have more time to properly plan for our future energy needs instead of the haphazard approach we currently have.

Geo Engineering – the various schemes mooted so far range from seeding the oceans with iron, painting every available surface (including mountain ranges) white, putting mirrors in space and injected vast quantities of sulphur into the atmosphere. Global cooling would be a far greater risk to life on this planet than warming, what happens if some bright spark says “yep, go ahead, shoot that sulphur up there and whilst your at it, throw a few mirrors up there too†and based upon the calculations of warming so far they get it catastrophically wrong because they’ve over-estimated how much emissions have warmed the planet.

I think I’ve gone on long enough; in fact probably far too long seeing as this is the Arctic discussion but you did ask….As you can see, there are many, many reasons why we need to know how much we’ve contributed to the warming of the planet, I can think of many more reasons than just the few listed above

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[jethro]

>> Weather in Tiksi, Russia today: Mostly Cloudy. High: 26 °C. Wind SW 22 km/h.

> Are you trying to illustrate a point there?

Thanks for pointing to other relevant stations, I'll make my point after I got an answer to the question: "How many trees make a forest?"

Depends where it is, what it is and how big it is. To comply to EU rules of classification it needs to be at least 05 hectares with a canopy closure of 20%. You plant Pine, you get more trees per hectare, plant Oak and you'll get less; the broad brush strokes used in climatology are no good for forestry, you need to provide specifics.