Scientists throw light on mysterious ice age temperature jumps

June 19, 2017, Cardiff University
climate
Credit: public domain

Scientists believe they have discovered the reason behind mysterious changes to the climate that saw temperatures fluctuate by up to 15°C within just a few decades during the ice age periods.

In a new study published today, the researchers show that rising levels of CO2 could have reached a tipping point during these glacial periods, triggering a series of chain events that caused temperatures to rise abruptly.

The findings, which have been published in the journal Nature Geoscience, add to mounting evidence suggesting that gradual changes such as a rising CO2 levels can lead to sudden surprises in our climate, which can be triggered when a certain threshold is crossed.

Previous studies have shown that an essential part of the natural variability of our climate during glacial times is the repeated occurrence of abrupt climate transitions, known as Dansgaard-Oeschger events.

These events are characterized by drastic temperature changes of up to 15°C within a few decades in the high latitudes of the Northern Hemisphere. This was the case during the last glacial period around 100,000 to 20,000 years ago.

It is commonly believed that this was a result of sudden floods of freshwater across the North Atlantic, perhaps as a consequence of melting icebergs.

Co-author of the study Professor Stephen Barker, from Cardiff University's School of Earth and Ocean Sciences, said: "Our results offer an alternative explanation to this phenomenon and show that a gradual rise of CO2 within the atmosphere can hit a tipping point, triggering abrupt temperature shifts that drastically affect the climate across the Northern Hemisphere in a relatively short space of time.

"These findings add to mounting evidence suggesting that there are sweet spots or 'windows of opportunity' within climate space where so-called boundary conditions, such as the level of atmospheric CO2 or the size of continental ice sheets, make abrupt change more likely to occur. Of course, our study looks back in time and the future will be a very different place in terms of ice sheets and CO2 but it remains to be seen whether or not Earth's climate becomes more or less stable as we move forward from here".

Using climate models to understand the physical processes that were at play during the , the team were able to show that a gradual rise in CO2 strengthened the trade winds across Central America by inducing an El Nino-like warming pattern with stronger warming in the East Pacific than the Western Atlantic.

As a result there was an increase in moisture transport out of the Atlantic, which effectively increased the salinity and density, of the ocean surfaces, leading to an abrupt increase in circulation strength and temperature rise.

"This does not necessarily mean that a similar response would happen in the future with increasing CO2 levels, since the boundary conditions are different from the ice age," added by Professor Gerrit Lohmann, leader of the Paleoclimate Dynamics group at the Alfred Wegener Institute.

"Nevertheless, our study shows that have the ability of simulating abrupt changes by gradual forcing as seen in paleoclimate data."

Building on this study, the team intend to produce a new reconstruction of global ice volume across the last glacial cycle, which will help to validate their proposition that certain boundaries can define windows of instability within the system.

Explore further: Iceberg armadas not the cause of North Atlantic cooling

More information: Abrupt North Atlantic circulation changes in response to gradual CO2 forcing in a glacial climate state, Nature Geoscience (2017). nature.com/articles/doi:10.1038/ngeo2974

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PTTG
3.4 / 5 (10) Jun 19, 2017
Before the denialist squad arrives:

"....temperature changes of up to 15°C within a few decades in the high latitudes of the Northern Hemisphere"

The high latitudes of the Northern Hemisphere are not the entire globe. This research shows that widespread and gradual environmental changes -- such as the increase in global average temperature -- has had sharp, localized changes as a consequence.
JongDan
2.6 / 5 (8) Jun 19, 2017
... so, how did that not completely kill off fragile ecosystems such as corals?
tblakely1357
2 / 5 (4) Jun 19, 2017
Caveman SUVs.
eljo
3.3 / 5 (11) Jun 19, 2017
Just for PTTG...and people needing to believe that C02 would be the only possible cause.

Or...it could be the sun that powered up slightly, and as a result the oceans warmed up a bit causing them to gradually outgas some C02. As the sun is pushing out more energy into the solar system, and is connected to the Earth-core electrically via our poles, the increase in arctic and antarctic birkeland current density, caused extra heating and salinity mixing by more energy going into driving the counter-flowing ocean currents, ocean currents that follow this contrarotating circle pattern typical of birkeland currents.

I am sure a computer model could be fabricated that produces the required historical result.

The increasing current density causes a massive temperature rise in the span of a couple of decades.

Why not invest some money in this line of research?

HannesAlfven
3 / 5 (8) Jun 19, 2017
Re: "Using climate models to understand the physical processes that were at play during the glacial periods, the team were able to show that ..."

What is the news here? A climate model was parameterized to create a runaway greenhouse effect. Why is this news? Nobody had any doubt at this point that the model could be created.

Now, back to the business of understanding all of the POSSIBLE causes ...
aksdad
4.1 / 5 (13) Jun 19, 2017
Nevertheless, our study shows that climate models have the ability of simulating abrupt changes by gradual forcing as seen in paleoclimate data.

Of course they do, but can they simulate the real world?

According to the most recent IPCC report, AR5 (2013), they can't. See for yourself:

https://www.ipcc....S-14.jpg

Notice how all the models predict temperatures higher than what the measured temperatures actually were? That means the models are wrong. Which means any secondary predictions based on those models are also wrong. They are no more accurate than examining sheep entrails to predict the future. That's how wrong they are.
MR166
2.6 / 5 (5) Jun 19, 2017
Wonderful, the Deep State is just a few itchy fingers away from the start of WWIII in the Middle East and people are still trying to hawk their AGW agenda. Be afraid, be very afraid because the Republicans, Democrats and the media have joined forces in the creation of the coming chaos.
orti
5 / 5 (3) Jun 19, 2017
First I've heard that D-O events were correlated to any CO2 cycles.
https://en.wikipe...er_event
Caliban
5 / 5 (6) Jun 19, 2017
They are talking about COOLING events in the northern hemisphere, which are well documented, and are not proposing any new events or mechanisms, but are actually saying that gradual increase in atmospheric CO2 drove changes in the climate which culminated in a sudden change --aka "tipping point".

No EUCC, and no conspiracy to monetize AGW into WWIII. This kind of willful disunderstanding is painful to watch, which would explain why so many are apparently unable to comprehend(or choose to willfully disunderstand) what is a pretty straightforward proposal.

@orti,
first time for everything -amirite?
unrealone1
3.4 / 5 (5) Jun 20, 2017
Axis tilt causes ice ages, Axis tilt causes Earth to heat and "cool"..
CO2 can only "trap" heat so there can be no cooling if CO2 is the "driver"..
Axis tilt is the driver of heating the Earth and cooling the Earth..
Water vapour is thousands of times more powerful than CO2 as a greenhouse gas so CO2 is irrelevant.
mauldred
5 / 5 (4) Jun 20, 2017
@unrealone1:
On one hand, water vapour does not naturally build up infinitely in the atmosphere. At temperatures typically encountered on the Earth it rains down if the partial H2O pressure reaches the saturation threshold.

On the other hand, CO2 is not a liquid in terrestrial conditions and doesn't rain down. There are some natural CO2 sinks (like the rainforests and oceans) but they can only remove it from the air at a certain rate that is much lower than the rate at which we produce it.

Water vapour DOES contribute to the AGW, but because higher air temperatures due to the accumulation of CO2 in the atmosphere increases the saturation threshold at which accumulated water vapour rains down, so it effectively increases the potential of the atmosphere to accumulate water vapour. CO2 is the kick-starter of the water vapour accumulation vicious circle, that's why CO2 is relevant.
Anonym
2.6 / 5 (5) Jun 20, 2017
Study is disingenuous. Ice cores show: First it warms, then CO2 levels increase. The most extreme global warming occurs in the Arctic, due to axial tilt. So of course the scariest warming occurs in the far North. Nothing. New. Here. At. All.

The catastrophists tell us CO2 has never been higher than it is now: where is the catastrophic warming? It gets lost in the El Nino signal, I suppose.
bschott
2.3 / 5 (6) Jun 20, 2017
On one hand, water vapour does not naturally build up infinitely in the atmosphere.

CO2 does? Actually, name one thing that can build up infinitely.....
Axis tilt causes ice ages, Axis tilt causes Earth to heat and "cool"..
CO2 can only "trap" heat so there can be no cooling if CO2 is the "driver".

You are in danger of displaying far too much logic here....
This kind of willful disunderstanding is painful to watch,

regarding the CO2 deathcult,yes...youarerite...
antigoracle
1 / 5 (3) Jun 20, 2017
Throwing light eh?
More AGW Cult bullshit.
Thnder
2.3 / 5 (3) Jun 20, 2017
Can't wait for a Methane conflagration of global proportions. All this worry and talk of CO2 and Water vapor, when Methane is where the fun is at...
Whydening Gyre
5 / 5 (1) Jun 21, 2017
Can't wait for a Methane conflagration of global proportions. All this worry and talk of CO2 and Water vapor, when Methane is where the fun is at...

And... "Don't lite that mat- !"
mauldred
3 / 5 (2) Jun 21, 2017
@bschott: I admit 'infinitely' is a bit strong but it can build up to reach very high extremes. Ever heard about Venus?
bschott
2 / 5 (4) Jun 21, 2017
@bschott: I admit 'infinitely' is a bit strong but it can build up to reach very high extremes. Ever heard about Venus?

If the earth was potentially subject to a "runaway" greenhouse effect, we wouldn't be here. That CO2 has been over 1000PPM in the past numerous times yet always managed to sink back down to preindustrial levels is an indication that it isn't a long term driver of temperature. Then we have a 15 year warming hiatus during a time when CO2 levels still rose...again, an indication it isn't a driver of temperature. Membership in the CO2 death cult requires a certain level of ignorance to basic scientific principles and a complete disregard for history.
IOW...belief, not science.
Whydening Gyre
not rated yet Jun 27, 2017
On one hand, water vapour does not naturally build up infinitely in the atmosphere.

CO2 does? Actually, name one thing that can build up infinitely.....

Does "Space" count...?
Whydening Gyre
not rated yet Jun 27, 2017
@bschott: I admit 'infinitely' is a bit strong but it can build up to reach very high extremes. Ever heard about Venus?

Mauldred,
There was a little more to the chemical make up of Venus' atmospheric demise than CO2...

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