(6) Global Catastrophes

Will a volcanic eruption destroy humanity? Scientists warn that world must begin preparing for explosive global catastrophe

Global catastrophe losses down in 2014

GC5

The good, the bad, and the downright mad

The good, the bad, and the downright mad No one on the planet is going to escape the effects of global warming, and for billions the resulting environmental deterioration is going to make life considerably more difficult. It is too late now to put the clock back, but we can at least attempt to alleviate the worst impacts of warming. The question is, will we ever be able to achieve a worthwhile international consensus that allows us to do this with any degree of effectiveness? The Kyoto Protocol gave us some hope in 1997, with its goal of a 5.2 per cent reduction of greenhouse gas emissions (below 1990 levels) by 2008–2012. Despite Russia’s ratification in 2005, however, the failure of the USA to become a signatory means that we have not progressed far from square one.

In fact, we are even worse off than this. Without US ratification, emissions from all the industrial countries put together could rise by about 12 per cent by 2008–2012, which is even higher than many ‘business as usual’ predictions. In terms of greenhouse gas emissions, things are getting steadily worse not better. It is difficult to see how this situation can improve until the United States – the world’s greatest polluter, emitting a quarter of all greenhouse gases – together with its almost equally profligate partner in crime –Australia – can be persuaded to join the rest of the international community in trying to tackle the problem. Personally, I suspect that, in terms of national governments, the only persuasion that will stand any chance of working will be the persistent pounding of eastern and Gulf Coast US cities by increasingly powerful hurricanes or perhaps a decade-long drought in Australia. There are, however, a couple of pieces of good news from the United States. By August 2005, 177 city mayors – including those of New York, Los Angeles, Chicago, and Miami – had signed up to the mayor of Seattle’s Climate Protection Agreement, which binds participating cities to strive to meet or beat the Kyoto Protocol targets. The same month, a group of nine northeast states – including New York, New Jersey, and Massachusetts – agreed to cap greenhouse gas emissions at current levels, with a goal of reducing them by 10 per cent by 2020. A small step, certainly, but a step in the right direction.

The more global warming continues to grab the limelight, so the more we hear from what I will call the ‘technofix tendency’. Some of their proposals for mitigating warming are wild and wacky, such as placing giant reflectors in space to divert solar radiation or, even more fantastically – and heaven forbid – diverting a comet or two past the Earth, using their gravity to swing the planet out into an orbit further from the Sun. Others are seriously thought-out scientific options that we may well have to adopt at some point in the future if the situation gets really out of hand. The latter include ways of using the oceans as a dumping ground for atmospheric carbon dioxide, either by physically discarding it in the deep ocean via pipeline and tanker, or by seeding the ocean with iron to encourage the growth of marine micro-organisms that extract carbon dioxide from the atmosphere. Pilot experiments have shown that both methods can work, but to operate on a large enough scale to make any difference they would be hugely expensive and require a concerted international effort that is difficult to foresee unless the current position becomes untenable. Furthermore, convincing public opinion that we need to mess about with the oceans in order to repair the damage we have wrought in the atmosphere would be a considerable PR coup. There is no doubt that if we are to have any impact on global warming we will all have to change our lifestyles, moving away from a disposable society and towards one that promotes and rewards the most effective and efficient use of available energy and resources. Tackling global warming is inextricably linked with the widespread adoption of sustainable development. Global warming will bring to an end the world as we have known it through dramatic changes to our environment, but if the situation is not to continue to slide it must also provide the incentive and impetus for changing the way we live. In the developed world we have no choice but to cut fuel consumption, invest in renewable energy sources, recycle on an immensely greater scale, and produce locally as much as possible rather than flying fruit and vegetables halfway around the planet. Much as I can understand their resistance, governments of developing countries must not follow the wasteful route to industrialization that Europe and North America have taken, for the simple and logical reason that if they don’t, they – and their people – will be the ones who suffer most. In particular, the developing world has to embrace renewable energy sources and recycling now, and the world’s economic powers have a duty to support them on this path. Despite the gloom over the failure of the Kyoto Protocol to be all-inclusive, there is an alternative plan to reduce greenhouse gas emissions on the table that might just start things moving on the long road to stabilization and even reduction.

Called Contraction & Convergence, or simply C&C, the new way forward was thought up by London’s Global Commons Institute. This ingenious plan is based upon two principles. First, those greenhouse gas emissions must be reduced and, second, that the means by which this is accomplished must be fair to all. C&C therefore proposes reducing emissions on a per capita basis.

International agreement will determine by how much emissions must contract each year, and then permits to emit will be allocated to all countries on the basis of their populations. The emission permits would be tradable so that countries such as the USA and Australia that could not manage within their allocations could buy extra ones from populous developing countries with a surplus. This remarkably simple scheme is daily attracting increasing interest, and now has powerful supporters in the UN, Europe, and China, and even amongst developing countries and US politicians. It is now inevitable that we and our descendants are going to face a long and hard struggle as our temperate world draws to a close and we enter the time of hothouse Earth. Perhaps, however, C&C can help to make the transition a little less desperate.

Facts to fret over

• By the end of this century the Earth is predicted to be hotter than at any time in the past 150,000 years.

• By 2100, global temperatures are forecast to rise by up to 8 degrees Celsius – or even more – over land, with sea levels up to 88 centimeters higher.

• Carbon dioxide concentrations in the atmosphere may be higher than at any time in the last 20 million years.

• In the year 2000, 1 in 30 of the world’s population was affected by natural disasters.

• By 2025, 5 billion people will live in countries with inadequate water supplies.

• Within 50 years all the world’s great reefs may have been wiped out by higher sea temperatures.

• The winter sports industry is unlikely to survive to 2100 in its current form.

• The probability of the West Antarctic Ice Sheet melting in the next two hundred years is 1 in 20. If this happens, all the world’s coastal cities will be drowned, from New York to London to Sydney.

The Ice Age Cometh

Fire or ice?

One of the main reasons for a growing disillusionment with science amongst the general public is the perception that scientists are always arguing with one another and constantly changing their minds. It is no use explaining that this is how science progresses, through battles between competing theses until the accumulation of evidence ensures that one triumphs and becomes an accepted paradigm. People want scientists to agree, to present a united front, and to tell them what is true and what is not. They want this because it makes life that much easier and gives them that much less to worry about. If you are concerned about your career or your marriage you don’t want to think about whether GM crops are good or bad, or whether you have to eat your beef on the bone or off, or whether your children’s children are going to fry or freeze. Here once again, however, the scientific consensus at least appears to have done another U-turn over the last couple of decades. The most maverick of climatologists now accept that the Earth is warming up rapidly and that our polluting activities are the cause. As recently as the 1980s, however, the big question in climatologically circles was when can we expect the next Ice Age? So what has changed? Well, actually, not much. The glaciers are still due to advance once again and we should expect our planet to be plunged into bitter cold within the next 10,000 years. What has changed, however, is the recognition that anthropogenic warming and its associated climatic impact may have a role to play at a critical time of natural transition when our interglacial world is due to give itself over to ice and snow for tens of thousands of years. Problematically, though, researchers are not quite sure what this role will be, and although, intuitively, you might expect global warming to delay or even fend off entirely the next Ice Age, some scientists have suggested that the ongoing dramatic rise in temperatures may actually accelerate the onset of the next big freeze. Even if the latter is shown not to be the case, we still have a problem. Knowing that a new age of ice is on the way should we not be trying actively to keep our planet warm? Should we not welcome global warming with open arms? In other words, we are currently faced with a stark choice that is only rarely voiced during the great global warming debate. How do we wish our familiar, contemporary world to end – by fire or by ice?

How to freeze a planet

During the Earth’s early history the surface boiled with lava oceans and exploding volcanoes, and although temperatures fell dramatically as prevailing geological processes moderated, our planet has been bathed in warmth for most of its 4.6 billion year history. Occasionally, however, a fortuitous combination of circumstances has heralded the formation of enormous ice sheets that have transformed a balmy paradise into a freezing hell. Artists’ impressions and television documentaries have ensured that most of us are familiar with the last great Ice Age, when mammoths roamed the tundra and our pelt-covered ancestors struggled to eke out an existence from a frozen world. Only recently, however, have studies of ice-related rock formations around the world brought to light a far more ancient and much more terrible period of refrigeration; a time when our planet was little more than a frozen snowball hurtling through space. Long, long ago, during a geological episode that is becoming increasingly and appropriately referred to as the Cryogenian (after cryogen for freezing mixture), the Earth found itself at a critical threshold in its history. It had cooled substantially since its formation over 3.5 billion years earlier and now the problem was keeping itself warm. At this time, between about 800 and 600 million years ago, the Sun was weaker and the Earth was bathed in some 6 per cent less solar radiation than it is now. Furthermore, the concentrations of greenhouse gases that are now heating up our planet – primarily carbon dioxide and methane – were not sufficiently high to hold back the bitter cold of space. Huge ice sheets rapidly formed and pushed towards the equator from poles, encasing all or most (this remains a bone of contention) of the Earth in a carapace of ice a kilometer thick. As the blinding white shell reflected solar radiation back into space, temperatures fell to −50 degrees Celsius and prospects for an eternity of ice seemed strong. But something must have happened to break the ice, as it were, otherwise I would not be here today to tell you about it; and in fact it seems that these ‘snowball’ conditions may have developed up to six times, succumbing each time to a return of warmer climes.

Just how the Earth managed to escape the clutches of the ice no one is quite certain, but it looks as if volcanoes might have been the saviours. After millions or even tens of millions of years of bitter cold, the enormous volumes of carbon dioxide pumped out by erupting volcanoes seem to have generated a sufficiently large greenhouse effect to warm the atmosphere and melt the ice.

Extraordinarily, life came through this particularly traumatic period of Earth history bruised and battered but raring to go, and hard on the heels of Snowball Earth’s final fling came the great explosion of biodiversity that marked the start of the Cambrian period 565 million years ago. Compared to the great freezes of the Cryogenian our most recent Quaternary ice ages come across as rather small beer. Nevertheless, although they affected smaller areas of the Earth’s surface, these latest bouts of cold were crucial because they coincided with the appearance and evolution of our distant ancestors. Furthermore, they may yet have a role to play in the future of our race. During recent Earth history the Sun’s output has been significantly higher than during the Cryogenian period and the level of carbon dioxide and other greenhouse gases has also been higher. Why then, at the end of the Miocene period about 10 million years ago, did glaciers once again begin to form and advance across much of the northern hemisphere? And more importantly, why, around 3 million years ago, did the southward march of the ice intensify? This remains a particularly hot topic in the fields of Quaternary science and environmental change and a detailed analysis of competing theories is beyond the scope of this book. Suffice it to say that explanations for the twenty or so ice ages that have gripped the Earth during the last 2 million years include disruption of the planet’s atmospheric circulation due to uplift of the great Himalayan mountain belt, and the drastic modification of the global system of ocean currents by the emergence of the Panama Isthmus.

Although one or both of these spectacular geophysical events may have contributed to a picture of increasing cold, the ice was already on the move, and we need to look elsewhere for the true underlying cause. What, in other words, turns ice ages on, and – just as importantly – what turns them off? This problem has intrigued scientists for many years and the solution was first put forward by the Scottish geologist James Croll as long ago as 1864 and expanded upon by the Serbian scientist Milutin Milankovitch in the 1930s. The Croll-Milankovitch astronomical theory of the ice ages proposes that long-term variations in the geometry of the Earth’s orbit and rotation are the fundamental causes of the blooming and dying of the Quaternary ice ages. In order for an ice age to get going, the astronomical theory requires that summers at high latitudes in the northern hemisphere are sufficiently cool to allow the preservation of winter snows. As more and more snow and ice accumulates year on year, so the reflectivity or albedo of the surface is increased, causing summer sunshine to have even less impact and accelerating the growth of ice sheets and glaciers. But how are the northern hemisphere summers cooled down in the first place? This is where the astronomy comes in. Cooler summers at high latitudes result from a reduction in the amount of solar radiation falling on the surface, and this in turn depends upon both changes in the tilt of the Earth’s axis and variations in its orbit about the Sun.

If the Earth’s axis was not tilted then we would not experience the seasons. During the northern hemisphere summer, for example, the North Pole is tilted towards the Sun, allowing more direct solar radiation to reach the surface in the northern hemisphere and raising the temperatures. In contrast, during the winter, the North Pole is tilted away from the Sun and the long, balmy days of summer are replaced by the cold and dark of a northern hemisphere winter. Now the southern hemisphere receives more direct sunlight with the result that those down under bask in warmth while the north shivers beneath gloomy skies. Although the tilt of the Earth’s axis averages about 23.5 degrees, it is not constant. Like a spinning top, the Earth wobbles – or processes – about its axis of rotation over a period of between 23,000 and 26,000 years. Furthermore, this wobble causes the amount of tilt to vary between 22 and 25 degrees over a period of 41,000 years. At times of least tilt, winters are actually milder, but more importantly, high latitudes receive less direct solar radiation and become cooler, making the survival of winter snows and the growth of ice sheets easier. On top of this there is another so-called astronomical forcing mechanism that contributes to the onset of ice age conditions. Like all planetary bodies, the Earth follows an elliptical rather than a circular path around the Sun, whose shape varies according to cycles of between 100,000 and 400,000 years. At the moment the Earth’s closest approach to the Sun occurs in January, when the North Pole is pointing away from the Sun, resulting in slightly colder northern hemisphere winters. Just 11,000 years ago, however, this closest approach – or perihelion – occurred in July, giving a small temperature boost to northern hemisphere summers.

Before this gets too complicated let me try and draw things together. Regular and predictable cycles – known as Milankovitch Cycles – are recognized in the behaviour of the Earth’s tilt and its orbit over periods of thousands to hundreds of thousands of years, and these cycles control the amount of solar radiation reaching the Earth’s surface and therefore its temperature. At times, a number of cycles may coincide so as to depress summer temperatures at high latitudes to a degree sufficient to allow the accumulation of winter snows. On its own this could not result in the huge ice sheets that have dominated the northern hemisphere for much of the last few million years, but as the area covered by snow and ice grows, so more and more sunlight is reflected back into space, accelerating the cooling process. This – in essence – is how ice ages start.

Conversely, at other times, the various cycles cancel one another out, the planet warms as a result, and the ice sheets retreat to their polar fastnesses.

Although Milankovitch and later researchers who have addressed the issue have been able to explain the mechanics of the ice ages and their periodicity, they have been less successful in deciding why these icy episodes appeared on the scene around 10 million years ago, rather than being apparent throughout Earth history. An answer to this may lie, however, in the carbon dioxide level of the Earth’s atmosphere, which has been steadily falling over the last 300 million years, from about 1,600 parts per million to just 279 ppm prior to the industrial revolution. It has been suggested that perhaps only when the level of carbon dioxide in the atmosphere drops below a critical threshold level – say of 400 ppm – is astronomical forcing sufficient to initiate the cycle of warm and cold that characterizes the ice ages. This begs the question that with carbon dioxide levels expected to rise above this level in a little over 20 years, have we seen off the ice ages forever? I shall return to this later.

In the meantime, on the basis that there is at least a fair chance that we will have to face them again at some time in the future, let’s examine what conditions were like in the depths of the last Ice Age. As temperatures started to fall around 120,000 years ago, so more and more of the planet’s water found itself locked up in mountain glaciers, polar sea ice, and expanding continental ice sheets in the northern hemisphere, with the result that sea level began to fall dramatically. Ice swept southwards towards the equator on at least four occasions over this period, with the peak of ice cover being reached a mere 15,000–20,000 years ago.

At this time sea level was a good 120 meters or so below what it is now – about the height of a 40-storey building – exposing new land bridges between continents and facilitating the migration of both animals and our distant ancestors. One of these land bridges developed across the Bering Straits, allowing people from Asia to cross into North America, from which, eventually, they colonized the New World. Just 600 generations ago, then, the north of our planet was in the steely grip of full glaciations with a third of all land covered by ice and 5 per cent of the world’s oceans frozen.

Compared to today, the environment at the height of the last Ice Age was desperately hostile, with mean temperatures 4 degrees Celsius lower than today but far lower at high latitudes in the north. In the UK, temperatures were reduced by between 15 and 20 degrees Celsius, transforming the country into a frozen wasteland with great sheets of ice reaching as far south as the River Thames and beyond. Some of the most inhospitable conditions were, however, to be found in North America, where temperatures over huge areas were 25 degrees Celsius lower than today and ice fields kilometers thick ensured that life was largely impossible.

Remarkably, however, just as it seemed as if the world might be returning to the ‘snowball’ state of the Cryogenian period, a surprising change took place. The planet started to warm rapidly, melting the great ice sheets at a rate far quicker than it took them to form. Melt water poured into gigantic lakes at the margins of the ice fields, which, in turn, emptied into the oceans, raising sea level and inundating land exposed just a few thousand years earlier. By 12,000 years ago, sea level was rising far more rapidly than even the most pessimistic forecasts for the next century, possibly by as much as 10 meters or so in a couple of centuries, and all the time the climate was becoming warmer and warmer – well, almost all the time that is. The journey from the depths of ice age to the current balmy interglacial was a rather bumpy one, and on more than one occasion the ice made a concerted attempt to reclaim centre stage.

Around 12,800 years ago, for example, the rapid retreat of the ice was stopped in its tracks as a new blast of cold initiated a thousand year-long freeze, known as the Younger Dryas to distinguish it from an earlier and less severe cold phase called the Older Dryas. No one is certain what caused this sudden cold snap but one suggestion is that the culprit was a huge discharge of fresh water from long-gone Lake Agassiz, one of the gigantic glacial melt water lakes that had accumulated in North America. The catastrophic emptying of this lake into the St Lawrence, and thence into the North Atlantic, may have disrupted currents carrying warmer waters into polar regions, allowing the climate at higher latitudes to cool and ice to form once again. The Younger Dryas and similar post-Ice Age cold snaps teach us a number of important lessons that we would do well to remember as our own world undergoes dramatic climate change. First, the switch from warm to cold and vice versa can occur extraordinarily rapidly – within decades – and second, the disruption of ocean currents can have serious and far-reaching consequences for climate change. 

Joomla Templates and Joomla Extensions by ZooTemplate.Com