Abrupt Climate Change; a clear and present danger to life on Earth

CLICK ABOVE to listen to discussion on the topic of abrupt climate change with Keelin Shanley on Today with Sean O’Rourke (broadcast 14th August 2015)

The Gulf Stream
The Gulf Stream is threatened by rapid melting of the West Greenland Ice Sheet, and if it was cut off, this could trigger rapid and severe global cooling (Credit: http://www.marketoracle.co.uk)

We tend to think of climate change as something which happens very slowly. perhaps over centuries, causing sea levels to rise a little perhaps or winter storms to get a little worse.

Perhaps this explains why there is no real sense of panic when stories come out about the latest appalling new threat to the stability of our global climate.

We have grown accustomed to such stories, and we don’t appear to believe that climate changes, which we all know are coming, will affect us too much in our lifetimes.

We tend to think of climate change as something which happens very slowly. perhaps over centuries, causing sea levels to rise a little perhaps or winter storms to get a little worse.

Perhaps this explains why there is no real sense of panic when stories come out about the latest appalling new threat to the stability of our global climate.

We have grown accustomed to such stories, and we don’t appear to believe that climate changes, which we all know are coming, will affect us too much in our lifetimes.

There is also confidence that human ingenuity, technology and engineering will come to the rescue to make sure that we don’t suffer too much inconvenience from any climate changes.

Yet, all this complacency is totally unwarranted, scientists believe, as there is plenty of scientific evidence to show that the Earth has gone through both rapid cooling and warming in the past; even before humans appeared on the scene.


Even some of the biggest creatures that ever walked the Earth have gone extinct due to very rapid climate change.

Most famously, there were the dinosaurs, but new research indicates in more recent times, rapid climate change was the primary reason behind the extinction of the Woolly Mammoth, a big, hairy elephant.

The Woolly Mammoth roamed large parts of the Earth for millions of years until its numbers declined 10,000 years ago, then disappeared about 4,000 years ago.

One of the most popular theories for why the Mammoth disappeared was because of over-hunting by hunter-gathering human societies.

However, the latest research indicates that the Mammoth, along with some bear species and cave lions went extinct due to rapid climate warming, not hunting.

At the end of the last Ice Age, the planet warmed by 16 Celsius in a matter of decades, then cooled, then warmed again. The Mammoth and other species couldn’t adjust.

The scientists examined Greenland ‘ice cores’, DNA studies from the bones of extinct Mammoths and the sedimentary record, and compared all of these.

The ice cores are taken by drilling deep into Greenland ice. This provides a geological record going back thousands, even millions of years into the Earth’s past.

The cores are a bit like tree rings, in that they can show when the climate has rapidly warmed or cooled and whether a volcanic explosion was the cause, or not.

Comparative DNA studies can tell you about how quickly a species disappeared, and what other species replaced it – which gives a clue to the extent of climate change.

It was not just the Mammoth that had trouble during this period of rapid cooling and warming about 12,000 years ago, lots of other species went extinct too.

The period from 10,900 BC to 9,500 BC is called the Big Freeze, or Younger Dryas as it’s known to scientists, where the Earth became very cold and experienced drought.

The onset of the Big Freeze, scientists believe, happened extremely fast, possibly inside a decade, and the end of the event was equally fast.

The evidence for this is seen in ice and sediments, and the fossilized remains of pollen and mammals.

As well as the Mammoths, many of the large vertebrates that dominated the last Ice Age died off during the Younger Dryas abrupt climate changes.

These included the short-faced bears, saber toothed tigers, giant sloths and mastodons.


These past climate changes had nothing to do with us, of course, but they happened very quickly, and saw enormous changes in global climate and sea levels.

Humans managed to survive the changes, probably because of their flexibility and large brains which made them better capable of finding survival solutions.

However, climate induced ‘mass extinctions’, such as the one that affected the dinosaurs, have wiped out more than half of the Earth’s life forms in the past.

It can, and will, happen again, the only questions are when? and how?


Most agree that we are entering a period of ‘natural’ warming, but there is also little doubt that mankind is pushing the natural warming cycle which is happening.

It’s important to draw a distinction here between ‘normal’ climate change, if you like, and ‘abrupt’ climate change, which happens faster, and is a lot more dangerous.

Abrupt climate change has happened inside a decade in the Earth’s past, and there is every reason to believe why the same couldn’t happen again.

Reputable climate scientists predict that the Earth will warm by an average of between 2 Celsius and 6 Celsius by the end of this century.

There is ‘normal climate change, if you like,  which is a worry in its own right, but then there is the far more ‘clear and present danger’ of abrupt climate change.

With ‘regular’ climate change, scientists believe that sea levels may rise by 2 metres and temperatures by about 4 Celsius, globally, by the end of this century.

These kind of changes over that period of time can be contained by mankind, using engineering and technology, although it won’t be easy or with massive costs.

For example, the best current estimates are that it will cost several billion to protect the city of Dublin alone from future likely climate events.

But, this is economics and maybe a century down the road, why do we need to worry now, you might ask? Don’t people have more pressing things to worry about?

Well, the worry is that the natural cycle of warming, when ‘pushed’ by human activities could push us past a ‘tipping point’ where climate changes rapidly.

The term ‘tipping point’ which was used during the Iraq war, when the statue of Saddam was torn down in Baghdad and people lost their fear of the regime.

[The origin of the term is from Malcolm Gladwell’s book called ‘The Tipping Point; How Little Things Can Make a Big Difference’]

With climate change it is similar. There can be an accumulation of factors, perhaps small in their own right, that push the climate past a ‘tipping point’.

In climate terms, the tipping point is when abrupt climate change is triggered, and mankind cannot control it, and no-one can predict the possible final outcome.

Rapid climate change ,can also be caused ‘natural’ events which are beyond our control, such as eruptions of ‘Supervolcanoes’, or being hit by comets.

Tipping point

Well, one possible scenario was depicted in The Day After Tomorrow, a Hollywood film from 2004, starring Dennis Quaid and Jake Gyllenhaal.

This is the most likely way that humans could ‘drive’ abrupt climate change.

In this film, which was based on real science, we see breaking off of a piece of the Larsen Ice Shelf, which is part of the Antarctic landmass.

At the same time, ice in the North pole floods into the North Atlantic, cutting off the North Atlantic Current, and disrupting other sub ocean currents.

In the real word, many scientists believe that the melting of the West Greenland Ice Sheet, which is underway, could also cut off this current.

The North Atlantic Current, is an extension of the Gulf Stream, which keeps Ireland ice-free, and without it, Europe and North America would become a tundra.

Allied to this, there are superstorms, which may believe would arise in this scenario, and the whole global weather pattern is thrown into chaos.

Many of the great cities of North America and Europe, – in the film – are buried under snow and ice, and US refugees, ironically, try to gain access to Mexico.

It’s Hollywood, it’s a film, but it’s based on real world climate ‘modeling’ scenarios, and the result was only parts of the globe remain habitable for human beings.

This is all largely down to mankind ‘pushing’ the climate cycle, by releasing carbon dioxide ‘greenhouse gas’ into the atmosphere and causing ice at the two poles to melt. However, tipping points have been reached in the past too ‘naturally’.

Lake Toba Location
The location of Lake Toba where the most recent Supervolcanic eruption took place. The emerging humans only survived in small numbers


The biggest threat, in the ‘uncontrollable’ category, by far, is of an eruption by a ‘Supervolcano’ – of which there are about six in the world.

The two most famous, which people may have seen on National Geographic or Discovery are the ones at Yellowstone in the US, and at Lake Toba, Indonesia.

If either of these went off, and there are others, like I said, we’d be in enormous trouble; all of us, not just those living in close proximity to the eruption.

A supervolcano is one which has an enormous amount of magma in its chamber and has the ability to cause devastation to a wide area and change global weather.

Let’s take Lake Toba. The last time it erupted was 74,000 years ago. Its impact was so colossal it caused a ‘volcanic winter’, with huge, and rapid cooling of the Earth.

This led to ‘mass extinctions’ of the majority of plant and animal species alive at the time, and early humans were one of the fortunate species to survive the event.

A Supervolcano is totally different to anything most people understand about volcanic eruptions, even the worst of them, going back hundreds of years.

For example, the eruption of Krakatoa in 1883, also in what is now Indonesia, killed 36,000 people – at least, and its explosion was heard 4,500 km away in Perth.

That famous eruption, caused a drop in global temperatures of 1.2 Celsius and a general cooling of the Earth’s climate for at least 15 years afterwards.

Consider this then:

Krakatoa expelled 45 cubic km of volcanic material. Toba expelled 2,800 cubic km, making it vastly more powerful and bigger than Krakatoa.

Frighteningly, Krakatoa’s eruption, which was tiny compared to Toba, was estimated to have the force of 200 mega tonnes of TNT explosive, compared to 20 mega tonnes for the Hiroshima bomb.

Toba, it has been estimated had 10,000 times the explosive force of Mount St. Helen’s which some might remember erupting in 1980, flattening all around it.

Scientists have linked the Toba eruption to a ‘Volcanic Winter’ which caused the planet to rapidly cool by 5 Celsius and to be plunged into a 1,000 year Ice Age.

The rapid cooling of the planet had an immediate and almost life-ending impact on early humans.

Scientists have reported that evidence from DNA studies has shown that the numbers of humans dwindled to a tiny number in the aftermath of Toba.

Researchers finally found an answer to the mystery of the ‘evolutionary bottleneck’ where the diversity of the human species shrank dramatically 74,000 years ago.

These kind of super eruptions are not as rare as we’d like to think.

Scientists have recorded at least 4 major Toba eruptions, and there are at least five other known Supervolcanoes; Long Valley, California; west of Santa Fe, New Mexico; Taupo Caldera, New Zealand; and Aira Caldera, Southern Japan.


The Sun is another element that has an important role, scientists believe, to play in climate change; even rapid climate change.

There is a solar cycle every 11 years during which there is a solar maximum when the Sun’s activity peaks and a solar minimum when it troughs.

There are also bigger solar cycles that go across centuries of time.

The simple way to measure solar activity is to look at its sunspots. The more sunspots the more solar activity, the less there are, then the less activity there is.

The “Maunder Minimum’ refers to a time when Sunspots almost disappear, and the sun’s activity is very low. Two Irish astronomers, Annie and William Maunder spotted this when looking at historical records, and their own observations.

Between 1645 and 1715 there was a Maunder Minimum when Sunspots disappeared, and the Earth cooled to the extent it has been called ‘The Little Ice AGe.

In London, for example, the Thames froze over in winter far more often than today, and a tradition of Frost Fairs grew up, which lasted into the 19th century.

As well as people doing business of all sorts on the ice, there were even ‘Ice Taxis’ to transport well-oiled revellers to and from their social engagements on the ice.

The Irish climate during this time, was like that of south western Iceland today, with average temperature year round of 6.8 Celsius compared to about 10 Celsius today.

Some business interests have tried to link all climate change, big or small, fast or slow, to solar cycles, and they deny the impact of mankind on it whatsoever.


Asteroids and comets impacting Earth are another thing to consider in this.

The biggest asteroid  impact to be recorded by geologists is the one which hit the Yucatan peninsula in Mexico 65 or 66 million.

This is called the Chicxulub impact crater.

This was large enough to cause mega-tsunamis, global firestorms, and trigger earthquakes and volcanoes, but also to cause rapid climate change.

A lot of carbon dioxide ‘greenhouse gas’ would have been released into the atmosphere from the breakdown of carbonate asteroid rocks like calcite.

This caused a very quick warming of the Earth, of a couple of degrees C, followed by a longer term cooling, as the dust from the impact blocked out the sun.

The dinosaurs, and most of the life then on Earth, couldn’t cope and went extinct.

The impact crater measures 180 km in diameter and is about 20 km deep.  That’s about the distance from Maynooth to Galway city diametre-wise.

The idea of an asteroid impact killing the dinosaurs was first proposed by Luis and Walter Alvarez in 1980, and it has since stood up to rigorous testing.

The impact resulted in the extinction of three-quarters of the other species of plants and animals on the Earth in one of the most famous ‘mass extinction’ events.

This wipe out opened the door to new species, mammals and ultimately to ourselves, as new creatures, better adapted to new conditions, began to thrive.

The extinction of most of life on Earth leaves opportunities for the few that survive.

What can we do?

Well, one thing we can certainly do is to reduce emissions of carbon dioxide before we push our climate past its ‘tipping point’.

I suspect, however, that it would take a colossal, rapid change in our climate for politicians and many people to wake up to the threat.

Unfortunately, that would be too late. It would be like trying to give someone a new cancer treatment when the disease has spread to all major organs of the body.

I would ask people to think again, and realise that abrupt climate is a real possibility and that if it is allowed to happen, no technology on Earth could reverse it.

In terms of the Sun and the impact of its cycles on global climate, there is not too much we can do, but we are getting better at predicting long term Solar cycles.

However, even if we face a Little Ice Age, as caused by the sun a few centuries ago, I’d be confident that we’d have the ability to survive it, although it wouldn’t be pleasant.

On comet and asteroid impacts. Again, scientists are getting very good at developing methods of warning us well in advance of something that could hit Earth.

I’d be confident here too, as, if we are faced with an asteroid about to hit us inside a few years or decades we will use our ingenuity to develop a way to divert it.

This could be by using lasers, or something else to nudge it slightly off its path, so that it swings by us.

The big threat, as with so many other things, to us from abrupt climate change is from our own activities, and this is where I worry about inaction.