Update: PDF of this paper is available, see link below
The fear that global temperature can change very quickly and cause dramatic climate changes that may have a disastrous impact on many countries and populations is great around the world. But what causes climate change and is it possible to predict future climate change? New research from the Niels Bohr Institute at the University of Copenhagen shows that it may be due to an accumulation of different chaotic influences and as a result would be difficult to predict. The results have just been published in Geophysical Research Letters.
For millions of years the Earth’s climate has alternated between about 100,000 years of ice age and approximately 10-15,000 years of a warm climate like we have today. The climate change is controlled by the Earth’s orbit in space, that is to say the Earth’s tilt and distance from the sun. But there are also other climatic shifts in the Earth’s history and what caused those?
Dramatic climate change of the past
By analysing the ice cores that are drilled through the more than three kilometer thick ice sheet in Greenland, scientists can obtain information about the temperature and climate going back around 140,000 years.
The most pronounced climate shifts besides the end of the ice age is a series of climate changes during the ice age where the temperature suddenly rose 10-15 degrees in less than 10 years. The climate change lasted perhaps 1000 years, then – bang – the temperature fell drastically and the climate changed again. This happened several times during the ice age and these climate shifts are called the Dansgaard-Oeschger events after the researchers who discovered and described them. Such a sudden, dramatic shift in climate from one state to another is called a tipping point. However, the cause of the rapid climate change is not known and researchers have been unable to reproduce them in modern climate models.
The climate in the balance
“We have made a theoretical modelling of two different scenarios that might trigger climate change. We wanted to investigate if it could be determined whether there was an external factor which caused the climate change or whether the shift was due to an accumulation of small, chaotic fluctuations”, explains Peter Ditlevsen, a climate researcher at the Niels Bohr Institute.
He explains that in one scenario the climate is like a seesaw that has tipped to one side. If sufficient weight is placed on the other side the seesaw will tip – the climate will change from one state to another. This could be, for example, an increase in the atmospheric content of CO2 triggering a shift in the climate.
In the second scenario the climate is like a ball in a trench, which represents one climate state. The ball will be continuously pushed by chaos-dynamical fluctuations such as storms, heat waves, heavy rainfall and the melting of ice sheets, which affect ocean currents and so on. The turmoil in the climate system may finally push the ball over into the other trench, which represents a different climate state.
Peter Ditlevsen’s research shows that you can actually distinguish between the two scenarios and it was the chaos-dynamical fluctuations that were the triggering cause of the dramatic climate changes during the ice age. This means that they are very difficult to predict.
Warm future climate
But what about today – what can happen to the climate of the future? “Today we have a different situation than during the ice age. The Earth has not had such a high CO2 content in the atmosphere since more than 15 million years ago, when the climate was very warm and alligators lived in England. So we have already started tilting the seesaw and at the same time the ball is perhaps getting kicked more and could jump over into the other trench. This could mean that the climate might not just slowly gets warmer over the next 1000 years, but that major climate changes theoretically could happen within a few decades”, estimates Peter Ditlevsen, but stresses that his research only deals with investigating the climate of the past and not predictions of the future climate.
Contact:
Peter Ditlevsen, climate researcher, PhD. Dr. Scient., Associate professor, Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, +45 3532-0603, +45 2875-0603, pditlev@gfy.ku.dk
Link to article in Geophysical Research Letters: http://www.agu.org/journals/gl/papersinpress.shtml#id2010GL044486
Update: PDF of full paper now available here
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Seems to me that we are already on a warm plateau, so if that’s true, it’s the cold trench (moat) that awaits.
Perhaps this might be called the “playground theory of climate”. With all the ups and downs, wild swings, and stuff being spewed here and there, and even with the big bully of climate – the Oceans, in the end, it is the Sun – the great Teacher in the Sky that calls the shots. Meanwhile, poor, barely-out-of diapers C02 stands cowering in a corner whimpering from time to time.
Sun Spot says:
August 30, 2010 at 9:24 am
Regarding the “10-15,000 years of a warm climate like we have today” , where are we in this time period today ?
Well the current interglacial started about 18,000 years ago (most common figure, study in Ireland reckons 19,000), so the glib answer would be “18,000 years in a 15,000 year period”.
Actually, the whole measurement of “ice ages” seems to be a mess, with some people seeming to count the various Dryas events and the gaps between them as interstadials during a glaciation, and other people counting them as stadials during a interglacial period.
The Younger Dryas (cold period) finished about 11,500 years ago, though there are persistant rumours that this may have been an impact event, and not due to climate cycles at all.
In short – pick a number – any number…
I had a quick read of that paper and I don’t think they are saying anything particularly remarkable. Chaotic systems cannot be predicted – they are their own fastest computer. The main issue of course is CO2 and whether it is a key parameter or a weak parameter in the global climate system. From everything I’ve read on WUWT and elsewhere, it seems to be an exceedingly weak parameter at best, uncorrelated with temperature. They don’t address this in the paper at all.
Can’t really comment on the quality of this paper as full text isn’t freely available and I suspect the article is a dumbed down version for non-experts.
Accurate prediction of future climate (100y+) is impossible due to the deterministic chaos which drives it. I suspect that both period doubling and several strange attractors are the cause of the quasi-cyclic oscillations we observe, and these are self similar at all temporal scales.
Perhaps one day in the future we will develop the data gathering systems and knowledge to make some useful generalised climate forecasts, but the current state of climate science is a long way from achieving this.
REPLY: see the update at bottom, full text provided – Anthony
Perturbing an unstable system is usually a bad idea.
What is missing is a demonstration that the climate is indeed a system that jumps between states.
CO2 is not a culprit in any of these rapid climate changes.
They cite 15 million years ago which was indeed 3C to 5C warmer than today but CO2 was only 200 ppm to 350 ppm for most of the time period (and as high as 450 ppm in one estimate at one interval).
If the Dansgaard events (12 of them in the last 100,000 years including the Younger Dryas which was clearly just another of these same events which) shifted Greenland’s temperatures by +/-13.0C as has been surmised, then CO2 certainly wasn’t responsible since it changed only modestly (enough for +/- 0.5C or so at 3.0C per doubling).
I don’t like these papers that operate through insinuation without showing the actual greenhouse effect implications of the data.
What we do know is that there are 100,000 year ice ages which change global temperatures by -5.0C and there is some other variation of +/- 2.0C at other times in the last 40 million years (and there are some very large changes (-13C to -20C) in the Greenland ice core proxies in the ice ages – while the other North Atlantic proxies just show the smaller (-5.0C and +/-2.0C) global temperature changes).
Again, the changes in CO2 over this entire time period going back 15 million years is only capable of explaining a very small part of the surmised temperature changes.
RE: ‘The “other” trench is a glacial period.’
Yep. Newsflash – the current NWS long range depicts a cold front slicing through Gerlach, NV, 1200 Z, Sunday 05-SEP. Things could be a bit “chaotic” for the partially to fully nekid Gaia worshippers out on “The Playa.”
What is missing is a demonstration that the climate is indeed a system that jumps between states.
Well that doesn’t need demonstration .
Sin(t) “jumps” between states of +1 and – 1 .
Chaotic pseudoperiodical oscilations “jump” between Max and Min states in the same sense .
The only point being that a chaotic system doesn’t “jump” between only 2 states like suggested by the figure .
If one considers that the climate evolves in a 5 dimensional phase space what several papers suggest then follows that every parameter oscilates chaotically between some Max and some Min .
So there are then 5×2 = 10 different states and the climate jumps chaotically between them .
Of course all this assumes that a “global” climate is a well defined system whose variables are spatial averages so that it depends only on time (and not space !) .
This is almost certainly a wrong assumption .
Simple people search for simple answers and tend to find simple and inexpensive solutions. Most simple people gravitate toward the simple and the inexpensive. A few simple people, who no doubt want to stand out in the crowd, espouse the simple and the expensive or, vary rarely, the complicated and the inexpensive.
Complicated people search for complicated answers and tend to find complicated and expensive solutions. Most complicated people are never a real problem, they tend to come to the very complicated conclusion that the simple people won’t back them up and they generally move on to another complicated area or subject to study. A few complicated people, who no doubt want to stand out in the crowd, espouse the complicated and inexpensive or, very rarely, the simple and expensive.
Most people are simple and inexpensive. Most politicians, economists, climatologists, and con-artists are very complicated and very, very expensive to simple people.
PS: Sometimes the best answer regarding a complicated process is a very simple answer: We just don’t know. Yet!
Well, plenty of dismissive comments, but this sort of description makes intuitive sense to me. Anyone who has worked with systems with multiple feedback mechanisms, both positive and negative, will recognise the same behaviour. It happens in complex electrical circuits, multi-component chemical reactions, ecosystems etc. Instead of a ball in a trench it’s more like a ball in a complex contoured landscape, like a badly made eggbox, or ski slope full of moguls. Applying some kind of forcing (which a 30% increase in CO2 is liable to do after all) will give the ball a push.
Whether that will be enough to drop it into the next trough? I personally don’t think any modelling is sophisticated enough to predict that in such a massively interconnected system. But a bird’s eye view of the major trends (global temps, arctic ice, yada yada…) and a quick shave with Occam’s Razor would seem to say ‘probably’.
“RE: TomVonk says:
August 31, 2010 at 4:35 am
If one considers that the climate evolves in a 5 dimensional phase space what several papers suggest then follows that every parameter oscilates chaotically between some Max and some Min .
So there are then 5×2 = 10 different states and the climate jumps chaotically between them .”
At the risk of being pedantic, that would be 2^5 different states – i.e. 32 possible stable climates. No wonder it fluctuates!
John Cook today came out with this. Can someone address it?
——————-
Quantifying the human contribution to global warming
http://www.skepticalscience.com/Quantifying-the-human-contribution-to-global-warming.html