According to this IPCC graph, the 4 most recent brief glacial intermissions have all lasted from 5% to 20% of the roughly 100,000 year glacial/interglacial cycle.
http://www.ipcc.ch/publications_and_data...
So major glaciation could be 6000 years past due or we could have 7000 to 8000 more warm years to enjoy before the next rapid cooling event.
Either way its nothing for any individual with a mere 120 year lifespan to worry about, or even notice.
Incidentally on the same IPCC graph you may notice that in brief history of the whole human race we have NEVER at any time been 50,000 or even 25,000 years away from the beginning of the next ice age !
I have no idea why The global warming industry started trying to push this ridiculous 50,000 year number a few years ago but something so easily disproved certainly doesn't help their credibility.
Interglacials last thousands of years.
There's absolutely no reason to think that in human lifetime terms we'll see any change because of a change in the shape of earth's orbit around the sun, which is what drives ice ages.
So, on that level, there will be no change at all.
However, the 40% increase in CO2 that's been added to our atmosphere will have an effect on the scale of human lifetimes. Not mine, but kids today will certainly see a warmer world than has been the case during my life.
You and I both know that you know better.
Is this what you'd like your children and grandchildren to see and think of you?
I don't think so.
Who are the "some scientists" who think we are "over due"?
The ice plates grow only when insolation is low enough during summer along the 65 parallel north that the ice does not melt. Those conditions occur due to the Milankovitch cycles of the earth's orbit and tilt. Those conditions will not occur for at least 50,000 years. Even then, the extended growth of ice plates requires a CO2 feedback; that is, at the beginning of an ice age the initial cooling from astrological factors causes the oceans to throw-off less CO2 and CO2 in the atmosphere drops, causing more cooling. It is impossible to predict what fuel sources the inhabitants of earth will be using in 50,000 years but with CO2 levels as high as now the interglacial would not end.
http://www.sciencedaily.com/releases/201...
If you take a look at the -40 Celsius weather we had in some parts of Canada and the US last winter, I'd say we're plunging face first into an ice age.
An ice-age cycle lasts for an average of 95,000 years with 83,000 of those years being the cooling phase and only 12,000 being warming.
The actual duration is influenced by Earth’s position within the various long-term climatic cycles it goes through. If the expected end of an ice-age coincides with a net cooling from the other cycles then the ice-age will last longer than usual. Conversely, the exit from an ice-age can be accelerated if it coincides with the warming phases of the other influential cycles.
Because the ice-age (eccentric) cycle is by far the most significant, the influence that other cycles have is relatively small. In terms of overall contribution to cyclical changes then the cycle of eccentricity accounts for a minimum of 72% of the peak variation in any one full cycle.
However, given that it’s extremely unlikely that all other cycles will simultaneously be in synch, and impossible for them to remain in synch, then the influence of eccentricity will exceed 72%.
Given the predictability of ice-age cycles we know with absolute certainty that we are nowhere near the peak of the next one and anyone who claims otherwise has completely lost touch with all reality.
People seem to think that the long-term cycles are unpredictable. They’re not.
Everyone is familiar with the cycles that cause the days and the years, no-one would be dumb enough to claim that next year will only be 300 days long or that tomorrow the Sun will set six hours early. But claiming that the next ice-age is just around the corner is no less stupid. There is no mechanism that influences the climate that could ever possibly allow for such a thing to happen.
The absolute worst-case scenario is that the primary cyclical climatic influence switches from eccentricity to precession – something that has never before happened. That being the case, then we would warm and cool across a 21,000 year cycle but the magnitude of such would be nowhere near enough to cause significant glacial and interglacial periods. That could only happen were there to be a switch such that the obliquity cycle became the dominant one, this is something that has happened before and theoretically could happen again.
If we were to suddenly find that obliquity was once again dominating eccentricity (i.e. it changed overnight) then we are still a long way from the peak of any glaciation. We are in the cooling phase of the obliquitous cycle and have been for 10,700 years but there’s another 9,800 years to go before we reach the minimum.
Were such a thing to happen then global weather patterns would moderate, winters would become warmer and summers cooler. Overall there would be global cooling with the range across the full cycle being approx 4°C. We are currently mid phase and therefore there is neither much warming or cooling attributable to axial tilt.
Take all other factors out of the equation and assume that axial tilt dominates, then in 10,000 years the planet will have cooled by 3°C, there will then follow 20,000 years in which Earth warms by 4°C before the cycle commences again (the figure of 3°C is the 2°C cooling from the neg phase of obliquity and the removal of the 1°C of global warming).
The magnitude of cooling coupled with the relatively short period of time that Earth would experience significant cooling means that the advance of glacial ice would be only a fraction of that associated with ice-ages. It would be more akin to another Little Ice Age when temps were 1.3°C less than they are now, than a full on ice-age when temps fall some 8°C less than current values.
Ignoring global warming, we are in the cooling phase of both the eccentric and obliquitous cycles. Obliquity will contribute to 10,000 more years of cooling before switching to the positive phase. The cooling signature from orbital eccentricity will completely dominate this and all that will happen is the rate of cooling will slow.
Taking into consideration the various different cycles and their future influences on our climate, the peak of the current ice-age cycle will be reached in about 73,000 years but because this coincides with the maximum warming associated with axial tilt then we can expect about 5°C of cooling compared to the mean of 7°C.
PS – Who are the scientists who think we’re overdue for an ice-age? Also, how do you figure that the current interglacial has lasted longer than most? No interglacial has ever lasted less than 12,000 years – the shortest is 20,500 years.
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EDIT: RE YOUR COMMENTS
“The shortest interglacial 20,500yrs is a plain lie”.
An intergalcial is the warmer period between two periods of glaciation, there is no single switch-over point, instead it’s transitional.
Glaciation starts off as a slow process, this is where we are now in the cycle. After about 50,000 years there can be an accelerated glaciation that lasts for about 20,000 years, for the remainder of the cooling phase, some 13,000 years, the glacial advance is considerably slower. Finally there’s 12,000 years of warming.
The interglacial can be considered to be the first 50,000 to 60,000 years, thereafter we enter the period when glacial extent starts to exceed it’s mean, this can be considered the start of the glacial.
On this basis, which is governed by Earth’s orbital eccentricity, the average interglacial would be 50 to 60,000 years in duration. If the last few thousand years coincide with the cooling phases consequent to other cycle then the intergalcial could be shortened to about 45,000 to 50,000 years.
This is the shortest interglacial we can experience at present.
Historically the obliquitous cycle dominated the eccentric one and ice-ages, such as they were, were dictated by a 41,000 year cycle with more equalised warming and cooling phases. Thus half the cycle could be considered to represent glaciation and the other half interglaciation. This is the fastest cycle that can influence ice-ages and therefore the shortest possible interglacial is 20,500 years long.
Please advise why you think it’s anything different.
“and nobody is saying we are in a peak of an ice age”
And if you read my original answer you’d know that I stated “the peak of the current ice-age cycle will be reached in about 73,000 years”, I fail to see how such a simple statement could be misunderstood.
“we are at a start of an ice age”
I know we are, I’ve said so many, many times over. In response to your question I stated that the cooling phase lasts 83,000 years and we have 73,000 years left before it peaks. Once again, it shouldn’t be hard to understand, so what’s the problem?
PS (again): Still waiting the names of those scientist who think we’re overdue for an ice-age. Surely you weren’t making things up.
Nobody knows.
Just as nobody knows how much longer the current economic upswing will last before the next recession, which does not, however, mean that business, economics, the stock market, and banking are all a giant hoax run by Greenie, Leftist conspirators for world government.
It will last until the yellowstone supervolcano goes off. And when the world warms up so grains and corn can be farmed on Greenland like the vikings did 1000 years ago I'd be thrilled.
I'd still like to see the calculated formula for CO2 rise that causes even 0.1C rise in the atmosphere. The one they claim causes a 1C rise with doubling is only in theory with no mathematics to really back it up. It's like Einstein's Theory of Relativity. You should be able to work a mathematical equation backwards to check your work and get an answer. How can one start with "infinity" and work backwards (Einstein's answer in his equation of relativity has an answer of "infinity")?
I don't think it will be in our grandchildren's grandchildren's grandchildren's grandchildren's grandchildren's grandchildren's grandchildren's grandchildren's grandchildren's grandchildren's grandchildren's grandchildren's time.
You would have to define what you would mean by the end of an interglacial. When the glaciers start their hundred thousand year advance or when they conclude their advance. In past glaciations, it took 100,000 years for glaciers to reach maximum extent.
some scientists think we are overdue for an ice-age, others think it wont happen because of our CO2 levels, whats your opinion?
I think 10-11 thousand years is typical gap. We are overdue. Perhaps we need more global warming.
