In his book A guide to the end of the world (subtitle: ‘Everything you never wanted to know’, 2002), Bill McGuire claims that three epic events await us. These are a volcanic super-eruption, a giant tsunami and an earthquake storm.
The last super-eruption was that of Toba in Sumatra about 73,000 years ago, which nearly exterminated our primitive ancestors. All that is left now is Lake Toba, but after the eruption, the ejected dust and gases covered the whole world and led to a ‘volcanic winter’ lasting 6-10 years, followed by a 1000-year long cooling period. Our modern civilisation is unlikely to survive such an event; there are food supplies for only 1-2 months! Yet there are several candidates for the next super-eruption, the obvious one being the magma chamber under Yellowstone Park in Wyoming (USA). Apparently it has erupted about every 650,000 years and last erupted 650,000 years ago; so it could erupt at any time from next week to next millennium. McGuire says that another unknown volcano could erupt at any time.
McGuire warns about a giant tsunami from the collapse of the west flank of Cumbre Vieja volcano on La Palma (one of the Canary Islands). This would cause widespread destruction including millions of deaths, especially on the east coast of the USA, where the wave would be 50 metres high. The US economy would collapse and there would be a global meltdown.
Japan and the west coast of the USA are especially vulnerable to earthquakes within the next 30 years; an earthquake storm would cause a recession and mass unemployment.
Let us not ignore the threat from space. McGuire says that there are 13 small asteroids capable of wiping out a major city that could hit Earth before 2100.
What about viruses like Ebola getting out of control? The human species could yet be wiped out by a disease for which we have no remedy.
Yet there is another threat to civilisation which we could prevent. I refer the so-called ‘global warming’ or ‘climate change’. These anodyne terms actually refer to the changes to climate, already evident, that, if unchecked, will destroy civilisation. That is because greenhouse gas emissions from burning fossil fuels is causing global temperature to rise.
In his book Climate Change (2003), John T Hardy explains that, even if carbon dioxide emissions were reduced to about to 1994 rates, the level will reach 500 parts-per-million by 2100 and that even if all emissions ceased today, the CO2 level would remain above pre-industrial level for 100 to 300 years. It has already reached 400 ppm.
Needless to say, attempts to reduce emissions are too little and too late. There is no hope that the world will get to grips with this problem; there will be hand-wringing and pathetic promises of minor action. Hardy thinks that CO2 levels will quadruple in the next few centuries.
Nor is CO2, the only culprit (contributing 60% of warming). Methane, although short-lived, is actually a more potent greenhouse gas (15.2%) and 20 per cent comes from other sources.
The result of all this warming will not only be more violent and erratic weather patterns (some already evident), but rising sea levels as ice sheets and glaciers melt. Sea level rise has been estimated to be on average +2.6-2.9 mm per year ± 0.4 mm since 1993. Additionally, sea level rise has accelerated in recent years. For the period between 1870 and 2004, global average sea levels are estimated to have risen a total of 195 mm, and 1.7 mm ± 0.3 mm per year, with a significant acceleration of sea-level rise of 0.013 ± 0.006 mm per year per year. If this acceleration remains constant, the 1990 to 2100 sea level rise would range from 280 to 340 mm. Another study calculated the period from 1950 to 2009; measurements show an average annual rise in sea level of 1.7 ± 0.3 mm per year, with satellite data showing a rise of 3.3 ± 0.4 mm per year from 1993 to 2009.
A study by the Potsdam Institute for Climate Impact Research (see http://advances.sciencemag.org/content/1/8/e1500589) has shown that burning all the world’s available fossil-fuel reserves would completely melt the Antarctic ice sheet, triggering a 61 m rise in sea level. This would happen if the global temperature rise above 2 degrees C.
A substantial rise in sea level will inundate coastal areas. About two thirds of the world's cities with over five million people are located in low-lying coastal areas. Future sea level rise could lead to potentially catastrophic difficulties for shore-based communities in the next centuries. For example, many major cities such as London, New Orleans and New York already need storm-surge defenses, and would need more if the sea level rose, though they also face issues such as subsidence. Can the world economy, operated from some of these cities, survive their flooding?
Another effect of rising carbon levels in the atmosphere is acidification of the oceans as they absorb much of the CO2. This is bad news for many marine species, who may not survive.
Are we doomed? Is there nothing that can be done? Of course global warming has two inter-related causes; the proliferation of greenhouse gases and insolation (heat from the Sun). So warming can be stopped, either by reducing greenhouse gases or by reducing insolation, or both. The former looks impossible—until it is too late. But the latter is possible.
Several methods of reducing insolation by climate geoengineering have been proposed. These are classed as ‘Solar Radiation Management’ (SRM) methods, which reflect a small percentage of the Sun’s radiation back into space. The Royal Society concluded that these methods act quickly, and so may represent the only way to lower global temperatures quickly in the event of a climate crisis. However, they only reduce some, but not all, effects of climate change, while possibly creating other problems. They also do not affect CO2 levels and therefore fail to address the wider effects of rising CO2, including ocean acidification.
Nevertheless, faced with the prospect of a global disaster, they have to be worth considering. SRM methods may include:
- Surface-based (land or ocean albedo modification); e.g. cool roof—using pale-colored roofing and paving materials.
- Troposphere-based, for example cloud whitening – using fine sea water spray to whiten clouds and thus increase cloud reflectivity. Such a method has been proposed Prof Stephen Salter of the University Edinburgh. He envisaged a flotilla of radio-controlled Flettner craft (using a vertical rotating cylinder for propulsion) spraying sea water as a low carbon alternative. As the water evaporates from the ultra-fine spray, the remaining grains of salt would provide the nuclei for low-level cloud condensation.
- Upper atmosphere-based: creating reflective aerosols, such as stratospheric sulphate aerosols, aluminium oxide particles, even specifically designed self-levitating aerosols.
- Space-based: space sunshade—obstructing solar radiation with space-based mirrors, asteroid dust, etc. This could be done in conjunction with a new space-exploration programme. We need to push on with this programme.
Mankind is in danger of destroying the complex technological civilization it has developed. Earth will survive, but perhaps not the human race.