In his book ‘Waking the Giant’ Professor Bill McGuire says, ‘Human interference in the natural world has consequences that are usually surprising and often unpleasant.’ As we consider the future scenarios of climate change that he spells out in his book, we might think this something of an understatement. The unpleasant surprise that he has in store for us is the link between climate change and geophysical responses – earthquakes, tsunamis and volcanoes.
After the Asian tsunami in 2004, some tried to label this tragedy as a climate change event, wanting to use the shock of the destruction to wake people up to the potentials dangers ahead. This was probably misplaced, and it enabled sceptics to dismiss such warnings as alarmists. Since then, geologists have looked seriously at whether climate change can affect the earth’s crust, what they have discovered, as summarised in Professor McGuire’s book, does not make comfortable reading.
First, to remind ourselves of the context: heat trapped in the atmosphere by increasing levels of carbon dioxide causes changes in the behaviour of the atmosphere, which in turn will cause changes to the water cycle. In other words, the climate will change. As James Lovelock has shown, all events, biological, chemical and physical are interlinked, so it is reasonable to ask whether a change in the climate, can have an effect on the solid Earth. While such a link seems at first glance unlikely, Professor Bill McGuire has shown convincingly that there is a link. His conclusion is clear, in a warming world there is a greater risk of seismic and volcanic activity, even small changes in climate can trigger significant geological events.
Through studying the geological record we now know that CO² levels in the atmosphere are as high as they have been for 15 million years and they have risen within the last 200 years. Global average temperature is now within 1°C of its highest for 1 million years. 2010 was the hottest year on record. Climate scientists are generally accepting that the likely rise in the global average by 2100 will be 4-6°C. In the high latitudes, this may be as much as 10-14°C. With this temperature rise, the ice caps and many of the world’s glaciers can’t survive. As a result there will be a significant transfer of water from the arctic and antarctic, where it mostly sits on land to the worlds ocean basins. This represents a transfer of weight from the ice-covered land to the oceanic crust. This weight transfer is how climate can affect the solid crust and the semi-solid mantle below.
At the end of the last ice age, 52 million cubic kilometres of ice melted, transferring the weight of this water to the oceans. This amount of ice exerted great pressure on the land and pushed it down into the earth’s mantle. It also suppressed movement in fault lines and volcanic activity. Free of this great pressure the land began to recoil, rising up and releasing the tension that had built up in geological faults causing earthquakes. Some of these earthquakes triggered huge landslips into the sea, causing tsunamis. This recoil effect will happen where ice is retreating leading to the heightened possibility of earthquakes and volcanoes.
Melt-water entering the oceans will put added pressure on the oceanic crust forcing it down. Between rising land and sinking seabed there will be a zone of tension where fault-lines will be subject to increased pressure, one such fault running parallel the coast is the San Andreas. Many of the world’s volcanoes are in coastal regions. Sitting under them are pockets of magma. Rising land and/or falling seabed squeeze these pockets up towards the surface, making it more likely that the volcanoes will blow.
One of the most rapidly warming areas of the earth is Alaska, and here the level of seismic activity is rising. The Bagley ice field has lost 1 km of ice over the last 20 years, the land is recoiling, triggering earthquakes. As the permafrost melts, landslips become more frequent and glacial lakes drain rapidly as the natural earth dams give way. In 2005 50 million cubic metres of rock and ice broke off mount Steller in southern Alaska travelling 9km at speeds of up to 100 metres per second. Fortunately, there were no communities along this path. Others have not been and will not be so lucky.
If the retreat of ice in the Arctic continues, it will trigger increased seismic and volcanic activity across the whole region. In 2010 the eruption of just one volcano, Eyjafjallajökull caused major disruption to international flights with a knock-on effect on the economy. As the ice retreats, more such events are likely. With ice and permafrost melting, sediments around the coast could become unstable, vulnerable to earthquakes. A major slippage of this sediment could trigger a massive tsunami, as happened at the end of the ice age, 8,500 years ago, sending a major tsunami crashing into the east coast of Scotland.
These changing conditions raise a further concern that the so-called gas hydrates that lie in deep cold water and under permafrost, could be disturbed and start to break down. Gas hydrates form when some gases, mostly methane join with water to condense as a solid under cold high-pressure conditions. If the conditions that keep them stable begin to change, through warming for example, they will break down, releasing their methane to the atmosphere. Methane remember, is about twenty times more potent as a greenhouse gas than carbon dioxide. Submarine landslides, triggered by earthquakes and melting permafrost, could also disturb the hydrates, resulting is a sudden explosive release of methane. Such sudden releases have been implicated in rapid climate change events in geological history.
There are between 10 to 30 years to save the arctic from irreversible melting that will trigger increased seismic and volcanic activity, with unknown impacts. In 2010, CO² emissions rose 6%, despite the global recession. The global economy is now going bust for growth and there is no significant or coordinated action to limit carbon emissions. As a result of big oil lobbying of the Durban Climate Change meeting in January 2012, no international action is planned until 2020. Climate change will happen because we are doing nothing to stop it. We can now add geological havoc to climate chaos. As Professor McGuire said ‘Things are going to be bad, if we do nothing they will be worse.’ Take your choice.
[based on a talk by Professor Bill McGuire Professor of Geophysical & Climate Hazards, UCL, given at the Peak Climate Festival 5th May 2012.]
Waking the Giant – How a Changing Climate Triggers Earthquakes, Tsunamis, and Volcanoes, by Bill McGuire, Oxford University Press, ISBN13: 9780199592265