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A Warning from the Past

21st century climate trends and tipping points

Andrew Glikson
Earth and paleoclimate science
Australian National University


The current rate of greenhouse gas rise is unprecedented in Earth history, excepting global volcanic events and asteroid impacts. The rise of atmospheric energy levels since the 18th century by 3.2 Watt/m2, masked in part by aerosols, leads the climate to over 2 degrees C temperature rise and meters-scale sea level rise.

Inherent in IPCC climate change projections are continuous trends toward mean global temperatures of 1.8 to 3.6 degrees C by 2100, depending on emission scenarios, as adopted in the Stern and Garnaut reports, giving an impression as if mitigation and/or adaptation can be undertaken at any economically or politically chosen time over the next several decades.

Unfortunately this is not the case.

Studies of the atmosphere-ocean-cryosphere (polar ice) system, based on evidence from ice cores, deep sea sediments, coral reefs, cave deposits and other proxies, demonstrate abrupt changes between climate states over periods as short as a few centuries, decades and even few years.

Central to such changes is the radiative forcing state of the atmosphere, namely the positive or negative balance between incoming energy flow (warming) and outgoing energy flow (cooling) associated with solar insolation, surface albedo, greenhouse gas levels (water vapour, CO2, methane, N2O, halocarbons, ozone) and aerosols (SO2, dust, sooth). Since the 18th century radiative forcing rose by near to 3.2 Watt/m2, predominantly due to emission of over 320 billion tons of carbon (GtC) and deforestation. Temperatures, ice melt and sea level rise lag behind radiative forcing by unspecified periods.

Interglacial periods (~410, 330, 240, 140 kyr) similar to the current Holocene (11.7 thousand years-ago [kyr] to the present) provide essential benchmarks for the behaviour of the atmosphere under rising radiative forcings (Figure 1 and 2) [1], [2].

Figure 1
CO2, methane, temperatures based on deep ocean measurements, calculated temperatures, greenhouse gas forcing, surface albedo and sea level changes over the past 800,000 years. From Hansen and Sato, 2011 [2].

Figure 2
Past global temperatures relative to mean Holocene temperature, based on ocean core records, with temperature change amplified by factor 1.5 (relative to Vostok-based estimates). Red arrow in upper diagram indicates temperature rise since 1750 consistent with the rise in atmospheric energy levels at 1.7 Watt/m2, indicating a committed rise of +1.2oC, or ~ +2.4 oC rise without aerosol masking effects.


Previous interglacial periods were up to 0.7 degrees C warmer than the mean value of the Holocene (Figure 2). For example a temperature rise at the Eemian, ~140 kyr ago was associated with sea level rise of about 5-7 meters relative to the present [5], setting a minimum for future sea level rise under current climate conditions.

Based on the study of ice cores and deep sea sediments, shifts between glacial and interglacial climates during the last 800,000 years (800 kyr) typically involved atmospheric energy changes of ~6.5+/1.5 Watt/m2, which is translated to ~5.0+/-1.0 degrees C (Figure 1). This defines a relation between temperature and atmosphere energy level of approximately 0.75 degree C per 1 Watt/m2 (Hansen et al., 2008 [1], 2011 [2]).

The 3.2 Watt/m2 rise since the 18th century, in the absence of SO2 aerosols, commits the climate to near 4 degrees C rise, exceeding previous interglacial periods (Figure 1). Such atmospheric energy levels can be compared with conditions which existed in the early to mid Pliocene (5.3 – 2.6 million years ago; <400 ppm CO2; T ~ +2 to +4 degrees C; sea level +25+/-12 meters higher than the Holocene) (Figure 2) and the mid-Miocene (~16 million years ago; <650 ppm CO2; ~4 degrees C; sea level +40 meters relative to the Holocene).

The expression of climate change through a series of extreme weather events around the globe, including heat waves, increased evaporation and precipitation and intensifying cyclone cells, remains little understood by the public. Lenton et al. 2008 state [3]: “Society may be lulled into a false sense of security by smooth projections of global change. Our synthesis of present knowledge suggests that a variety of tipping elements could reach their critical point within this century under anthropogenic climate change.” (Figure 3)

Figure 3

Map of potential tipping elements in the climate system, overlain on global population density. Subsystems indicated could exhibit threshold-type behaviour in response to anthropogenic climate forcing, where a small perturbation at a critical point qualitatively alters the future fate of the system (Lenton et al. 2008 [3]). http://researchpages.net/esmg/people/tim-lenton/tipping-points/

While the timing of tipping points cannot be determined, such may be preceded by lulls, as indicated by Dakos et al., 2008 [4] (Figure 4): “…we analyze eight ancient abrupt climate shifts and show that they were all preceded by a characteristic slowing down of the fluctuations starting well before the actual shift … our results imply independent empirical evidence for the idea that past abrupt shifts were associated with the passing of critical thresholds.”

Figure 4
Reconstructed time series of abrupt climate shifts in the past. The arrows mark the width of the moving window used to compute slowness. The smooth grey line through the time series is the Gaussian kernel function used to filter out slow trends. Dakos et al.,2008 [4]. http://www.pnas.org/content/105/38/14308


The amplifying feedback mechanism of polar ice melt is the so-called albedo-flip effect, where loss of reflection by melted ice is compounded by infrared absorption by open water, a process currently taking place in the Arctic Sea, as reported by Hansen et al. [1], [2]: “… amplifying feedbacks make ice sheet disintegration necessarily highly non-linear. In a non-linear problem, the most relevant number for projecting sea level rise is the doubling time for the rate of mass loss. Hansen (2007) suggested that a 10-year doubling time was plausible, pointing out that such a doubling time from a base of 1 mm per year ice sheet contribution to sea level in the decade 2005-2015 would lead to a cumulative 5 m sea level rise by 2095.”

Satellite studies of Greenland and Antarctic ice melt rates by Velicogna, 2009 [6] and Rignot and Velicogna, 2011 (cited in [2]), who indicate acceleration of Antarctic and Greenland ice melt rates, forming major contribution for sea level rise.

It is not generally realized that, through rising atmospheric CO2 levels since ~8000 years ago due to fires and deforestation, and rising methane since ~5000 years due to rice cultivation and animal husbandry, civilization has subconsciously postponed climate cooling toward the next ice age by near-2.7 degrees Celsius [7]. Judicious science-based injection of greenhouse gases into the atmosphere would have been able to prolong interglacial Holocene conditions, justifying the term “Homo sapiens”.

Instead, since the mid 18th century, uncontrolled release of fossil carbon from hundreds of million years-old fossil biospheres at <2 ppm/year, a rate unprecedented in geologic history (barring major volcanism and asteroid impacts), is pushing mean global temperatures toward climate conditions of millions of years ago when tropical conditions dominated much of the Earth and large parts of the continents were covered by seas.

We are simply talking about the very life support system of this planet

Joachim Schellnhuber, Director of the Potsdam Climate Impacts Institute:

[1] http://www.columbia.edu/~jeh1/2008/TargetCO2_20080407.pdf

[2] http://www.columbia.edu/~jeh1/mailings/2011/20110118_MilankovicPaper.pdf; http://climateprogress.org/2011/01/20/hansen-sato-climate-tipping-point-multi-meter-sea-level-rise/

[3] Lenton et al. 2008.


[4] Dakos et al.,2008. http://www.pnas.org/content/105/38/14308

[5] http://eis.bris.ac.uk/~glyms/Siddalletalbook2005.pdf

[6] http://www.agu.org/journals/ABS/2009/2009GL040222.shtml


http://www.ingentaconnect.com/content/klu/clim/2003/00000061/00000003/05145667 , http://www.springerlink.com/content/p80k8m717qm01710/

[8] http://www.ipcc.ch/publications_and_data/publications_and_data_reports.shtml

[9] http://www.sciencemag.org/content/326/5958/1394.abstract


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Tectonic plates and climate change


Long-term climate change could be responsible for moving the Earth's tectonic plates.

A team of scientists based in Australia, France and Germany has established a link between monsoons in India over the past 10 million years and the motion of the Indian plate.

The scientists have found that as monsoons in the area increased the plate moved by almost one centimetre a year.

The researchers say it's the first time climate change has been recognised as having the potential to influence the motion of tectonic plates.

Earthquakes and global warming

Fiona, more food for thought.

“What happens is the weight of this thick ice puts a lot of stress on the earth. The weight sort of suppressed the earthquakes, but when you melt the ice the earthquakes get triggered.”

Another geologist, Bill McGuire of University College in London, is quoted as saying, “All over the world evidence is stacking up that changes in global climate can and do affect the frequencies of earthquakes,volcanic eruptions and catastrophic sea-floor landslides. Not only has this happened several times through Earth’s history, the evidence suggests it is happening again.”

Maybe we are underestimating the cost of global warming.

More reason to take a cautious approach and reduce our levels of C02 pollution until we really understand the effect human activity is having on the planet.

Fiona: I would be really interested in Andrew Glikson's comments on these two pieces of research, John.

The Anthropocene or the Age of Mankind

One of Australia's leading climate change scientists, Will Steffen, takes us on a journey through the science of measuring humanity's effect on the planet. Using tangible, real measures, Steffen shows the profound change in the planet since the Industrial Revolution.

He argues that now, more than at any other time, humanity is the single most influential factor in global changes, so much so that we should recognise that now is "the age of mankind" - or what he likes to call "The Anthropocene".

Much of the debate around climate change centres around the fact that the Earth is changing (it has always been changing). If we agree that the Earth is changing (warming) is the change caused by human activity?

Will Stefffen argues that the world is changing and that humans are the cause of a lot of this change.

If we accept Will Steffen's argument then we must accept responsibility for the changes and make sure we do not cause change that may make the planet a harder place for our children to survive.

A Tax On Sanity

Scott Dunmore: "I'm not a climate change sceptic as you know; it's always been changing."

I can't ever recall anybody (sceptics included) claiming the climate hasn't always changed. The argument is about how much humans can influence that change.

Apparently a world tax will eventuate in the perfect climate, although nobody is saying what that will be. It's also apparent nobody knows how we'll all know we've made the target. A bit hard when nobody knows or is saying, what that climate target is.

Who knew a tax could solve such large world problems? We could move on to a tax for eternal life. A tax for time travel. Fuck, a tax for the meaning to life.

With every passing year, I wonder more and more, if I'm getting older or the world's getting dumber.

Both Liberal and Labor will use tax to reduce c02

Paul, the Liberal party's plan to reduce our C02 emissions is to use TAX payers money and give billions to the major polluters in a hope that they may cut their emissions. If they have any TAX payers money left after giving it to their rich mates they will then give some to develop alternative energy. (Trying to pick winners).

The Labor party's plan is to TAX the big polluters (about 1,000 of them).

This will make coal more expensive and encourage them to change to alternative energy sources.

The TAX collected will be given to the poor (you know, just like Robin Hood).

Any left over will be used to support emerging alternative energy.

So most of us would be better off under the Labor plan.

As to the the question will either TAX make a difference to the global climate? Probably not.

That is not the point, what both parties hope to achieve is to move Australia away from fossil fuels to clean alternative energy.

The world is running out of fossil fuels (check the price of oil). We need to move away from our addiction to fossil fuels. The countries that move first will create hundreds of thousands of new jobs in new industries.

Eventually all energy will come from clean sources (Including nuclear).

Then over time the levels of C02 we pump into the atmosphere will drop to "normal" levels and the human influence will be reduced.

If we continue to delay our move away from fossil fuels the cost to change will be higher and spread over a shorter period the damage to the economy will be greater.

We must change, we will change and TAX is one way of encouraging us all to change. That is the reason ALL political parties are going to use TAX payers money to make alternative energies more competitive with dirty stinky deadly fossil fuels.

GOM syndrome

" I wonder more and more, if I'm getting older or the world's getting dumber."

You're not Robinson Crusoe there Paul old son.

This mange is making me thirsty...

The disease of humanity...

From where this cranky old vombatus ursinus sits the "disease of humanity" is what we call the mange, and does it drive one to distraction (you've probably noticed).

Butt what you humans have most likely not noticed is that all the forna, except those bloody lazy self obsessed cats, want you dead, the sooner the better in fact.

And I bet you haven't got a clue that those mammals you label baboons are running a book on just how long it will take before you lot do yourselves in.  And I bet you also don't know we non-humans are planning the biggest shindig Planet Earth has ever seen as soon as the very last human exhales for the very last time - good riddance to bad rubbish.

How long have you lot been here?

Think about it, in no time at all you have trashed our home, eaten many of us non-humans alive or dead, killed for fun, left your crap laying around like a bunch of ill-breed hillbillies from Tasmania, and spread diseases like Charlie Sheen at a church fete.

I'm not a betting wombat, besides those bloody baboons have been known to welsh on their bets anyway, butttttt I do plan on joining in on that post wise-man (you really do have a problem) piss up.

BTW, They say real estate is very cheap on Mars; why not relocate there, immediately, and do the rest of us one very big favour - besides we non-humans know you lot have, especially over the past couple of hundred years, totally divorced yourselves from the real world; you have disconnected yourselves from that which is natural by trying to be super-natural (all powerful - immortal?). It's probably an ego thing but for some reason or another it's only humans that suffer from such an affliction - the nature of the beast I suppose.

For the betting non-human I reckon April 2157 would be a safe bet - we can't wait.

The disease of humanity?

Jay, I try to understand this stuff, yet every time I try to digest I still hear "We'll all be ruined, sad Hanrahan" every time.  Andrew's obviously gifted in his presentations, but I still can't help wondering if the Climate Change paranoia is vindicated.

Nothing stays the same.  If humans are a part of nature, then aren't the climates we create "natural"?   It might be just my ability to comprehend, but I'm still have trouble being convinced to become concerned that what's happening isn't in the natural order of things.

Then again, to paraphrase Kurt Vonnegut, Climate Change could well  be Nature's way of curing itself from the disease of humantity. Dunno...

Of mice and men

"then aren't the climates we create "natural"?'

Well  Richard, it depends on what you call "natural"

I'm not a climate change sceptic as you know; it's always been changing. Whether or not we have any impact on it is another matter and I have little doubt that we do. Is it carbon emissions though or simply the heat energy of billions of years of sunlight that we release that is causing it? Not enough is known.

Nature acts in a way similar to markets. Sometimes it gets it wrong with pest plagues that nearly wipe out other species, flora or fauna. Food and space and water run out and a very natural correction is made. Boom and bust and as you know I think humans are near the end of their boom. Not in my lifetime but my forty year old sons I think, will experience a different world in their twilight years.

Understanding climate science

I find it quite easy to understand, Richard, by stepping back a bit, and adopting a slightly skeptical attitude to everything.

Kevin Rudd sold us on an international carbon trading scheme. We were feeling rich at that time, it made sense and we said ok. Unfortunately, for all his Mandarin and foreign affairs expertise, he was incredibly naive. The developing world, and in particular China, are no longer able to be intimidated, bribed or bamboozled into acting against their own interest.

To save face, Rudd decided to go solo. A trading scheme for a pollution based economy isn't a very good idea, we had had the crash. Julia and Wayne realised this, and scuttled Kevin's hobby-horse.

Then came the elections and Julia got into bed with Bob.

Julia is desperate to stay in office. So she has cooked up a scheme where she takes money  and gives it right back, particularly to those who scream the loudest. So, guess what? Everybody screams loudly.

The issues have nothing to do with climate science, and everything to do with how democracy works. We are debating the wrong topic.

Rudd is not going solo!

Jay: "Rudd decided to go solo."

Rudd is not going solo.

The EU and its 30 member countries started an emissions trading scheme in 2005.

New Zealand’s emissions trading scheme began last year.

States in the US and Canada have introduced their own trading schemes.

India last year introduced a tax on coal as an initial measure aimed at cutting emissions.

Birds seldom differ

Fair comment, John. Though I would suggest that some countries individually deciding to fly roughly in a similar direction, to different destinations is not really flying together, much less flying in formation.

All rivers start as a rain drop

Jay, all rivers start as a rain drop. The abolition of slavery started one country at a time.

Slavery had been abolished in England in 1772 and Britain had outlawed the slave trade with the Slave Trade Act in 1807, with penalties of £100 per slave levied on British captains found importing slaves (treaties signed with other nations expanded the scope of the trading ban). Small trading nations that did not have a great deal to give up, such as Sweden, quickly followed suit, as did the Netherlands, also by then a minor player, however the British empire on its own constituted a substantial fraction of the world's population.

We will eventually give up fossil fuels and it will be one country at a time.

Those that move first will have the advantage of selling new technologies to the nations that are slow to move.

That is why I think Australia should be among the first to move to clean energy and sell the technology to the world.


One can also point out, John, that most rain-drops don't make it to rivers. To be even more pedantic, some rivers in oceans do not start off as raindrops, some rivers on land start off as springs.

It's surprising how much the government proposal has gotten me angry, considering that in fact, I mildly support an ETS (i.e. I think an ETS is nice to have, but far from a priority (ie I'd vote for an ETS, but not put much energy into promoting it)). 

The big lie

Jay, it is not entirely surprising that something has "gotten" (urgh, Americanisms) you angry, but you might be astray in your attribution of blame. Mungo MacCallum has some wise words that you might like to consider:

[Gillard’s] case is unassailable: even those who profess to find the science of climate change unproven agree that if you are going to halt the increase of carbon dioxide emissions, the only effective way to do so is to put a price on carbon.

The only remaining dispute is about whether you do so through some kind of emissions trading scheme or through a direct tax. In Australia, politics decrees that the best approach is to start with the tax and develop it into a trading scheme as conditions change. It is straightforward, effective and above all affordable; when a large part of the tax is returned to consumers as compensation for the inevitable price rises, the rich will barely notice the difference and some of the poor might even finish up ahead. Selling it should be like giving away free beer.

But Gillard, so far at least, has not been able to counter Tony Abbott’s constant channelling of Hanrahan: we’ll all be rooned. This is partly because Abbott’s sloganeering seems to the incurious to be borne out by actual events. It’s still more than a year before any effects from the proposed carbon tax will kick in, but already prices, particularly electricity, petrol and food, appear to be going through the roof. At least some of the increases are actually due to delays in implementing the tax, but Abbott and his colleagues have quite consciously and deliberately adopted the strategy of blaming the tax for everything: the big lie is, as always, the simplest approach.

And as scare campaigns go, it is going pretty well and it will continue to flourish unless and until Gillard and her colleagues can come up with some hard numbers to counter it. And by then, if Abbott can establish a public mood of fear and mistrust, it may be too late. Having paid his respects to his personal God every evening, Abbott must also breathe a prayer of thanks to the fridge magnet that gave him the idea: I didn’t say it was your fault, I said I was going to blame you for it.

My emphasis

Julia of Arc's shell game

Fiona, you are quite right. Gillard's case is unassailable. If she doesn't agree to a tax, the Green's will throw her out. If she doesn't hand it right back to the polluters, they will throw her out at the next election. No one can argue with her reasoning. 

As John himself has acknowledged, the current proposal is not going to make any difference to global warming. John's real goal seems to be to make Australia into a leading alternative energy manufacturing nation. I'm not against this goal, but am far from convinced that the tax will achieve this. There are much smarter and more efficient ways to become a leading manufacturing nation in niche industries. However, what is certain, is that the tax is going to kill domestic manufacturing in all other industries. Foreign companies are going to flood Australia with cheap imports. I bought some frozen vegetables from a trusted Aussie company, and find it's actually from China. It's cheaper to ship produce frozen from China, and it's going to be even cheaper in the future! The country with poisoned baby milk powder! 

If Gillard had a carbon tax and kept the money to get us into surplus, I'd applaud. But we should be too old to fall for the shell game she is trying to pull. 

 If Gillard had a global conscience and was actually trying to reduce climate change, I'd support her. Or at least if Gillard had a national conscience and was doing what was good for Australia. The problem I have is that she is doing what is good for Gillard. You make the exact point elsewhere - where is the leadership?

At least Kevin Rudd and Malcolm Turnbull come across as being honest.

The water cycle

Jay, all springs come originally from rain drops. All rain drops eventually end up in the ocean. A spring is an underground river on its way to the ocean.

The push to alternative energy will one day be a mighty river on its way to the ocean. The carbon tax is a first drop on the river to an ETS. Polluters should pay for the clean up, simple and fair.

One day we will live in an ocean of clean energy.

Simple Simon says

My understanding of this article is that it states that current climate projections are too conservative, that real temperature rise is likely to be much higher, and bases its conclusion on two arguments:

1. Firstly current models suggest that the earth has been absorbing a lot of energy, more than can be accounted for by the current temperature. This energy is going to leap out of wherever it is hiding, and temperatures are suddenly going to shoot up without warning.

2. Secondly, IPCC models show climate changing smoothly. However, history indicates that changes are not smooth, but rather bumpy. We should ignore the IPCC's smoothing effort. Rather, we should add all the up bits and ignore all the down bits. This will give us a much more useful prediction.

Have I got it right? I found the article fascinating but difficult to understand, and would be happy to be corrected.

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