symmetrical photomontages of landscapes touched by humans. The title of his body of work is “Anthropocene.”58
In addition to our increase in numbers and our growing imprint on the surface of the earth, the third characteristic that marks the end of the Holocene is our enormous energy consumption and its consequences for the global climate. World population has increased by a factor of 5.4 since 1860 but energy consumption has increased by a factor of 41, in the same period. On average, each individual now consumes the equivalent of half a gallon of petroleum—per day.59
The signature of humans is becoming visible on land in the form of shale fracking, in the oceans in the number of deep-sea drilling rigs and in the sky with a wide range of new chemicals in the atmosphere. From regional phenomena, like the huge Asian “Brown Cloud” that hangs over megacities in China to the carbon dioxide emissions accumulating in the atmosphere from millions of individual sources, humans are creating a new physical reality.
Since the beginning of industrialization humanity has been running a gigantic geophysical experiment. People have been mining coal and petroleum from earth’s crust, burning them and dispersing the resultant carbon dioxide into the atmosphere for some time. Carbon is also released into the atmosphere when forests burn down or wetlands dry out. According to estimates by the Potsdam Institute, Oxford University and the World Resources Institute, an additional 2,110 billion tons of carbon dioxide went into circulation between 1800 and 2014 as a result of human activities.60 This already represents a significant disturbance of the earth’s carbon cycle.61, 62 Despite global efforts, carbon dioxide emissions are still increasing; for energy consumption alone, emissions stood at 34.5 billion tons in 2012 and 36 billion tons in 2013.63, 64
If current trends continue, then from the beginning of industrialization to approximately 2025, the same quantity of additional carbon, in the form of carbon dioxide, will have been introduced into the atmosphere and oceans by humans, as is contained in all living organisms today.65
Around sixty per cent of this colossal quantity of material is absorbed by the oceans and vegetation for now; because carbon dioxide dissolves in water and plants can absorb it and convert it into biomass. But that does not mean that the element has disappeared. In the sea, acidification has already started to take place because carbon and water combine to form carbonic acid, as everyone familiar with chemistry or fizzy drinks well knows.66
If you’ve ever downed a soft drink with too much carbonic acid, you get an idea of how countless sea organisms must feel as they are disturbed by carbon dioxide. Carbon dioxide has a slightly corrosive effect; organisms partly composed of calcite—like plankton or coral reefs—are extremely vulnerable to this. Coral reefs and the shells of organisms like diatoms, which are at the beginning of the food chain, are therefore endangered by acidification, which leads to the coral bleaching. While there are methods by which coral reefs buffer acidity, this is only possible to a certain extent.67 The negative consequences of acidification are considerable because of how they affect the marine food chain.68
This development worries me much more than higher temperatures on land. The oceans cannot absorb unlimited quantities of carbon dioxide and, if a tipping point is ever reached, warmed seas could change from being repositories of greenhouse gases into becoming sources of greenhouse gas emissions. If the seas become warmed to their depths, and there are already indications that this is happening, frozen methane gas could thaw and be released into the atmosphere. Methane is a much more potent heat-trapping gas than carbon dioxide.69, 70
At the beginning of industrialization, the concentration of carbon dioxide in the atmosphere was around 280 parts per million molecules of air (ppm). At the time of the UN Climate Summit in Rio de Janiero, Brazil, in 1992, it had reached 356 ppm. In May 2013, at the monitoring station on the summit of the Mauna Loa volcano on the Big Island of Hawaii, the value exceeded 400 ppm, and according to current trends it will reach 440 ppm by 2040—a threshold that climate researchers regard as critical.71
Scientists from the Intergovernmental Panel on Climate Change (IPCC) continue to agree that emission of greenhouse gases caused by humans will increase the earth’s average temperature by at least two degrees Celsius by the end of this century. Apparent breaks in global warming trends appear to have more to do with complicated feedback mechanisms between the atmosphere and the oceans and a lack of measuring stations in the Arctic, rather than with incorrect scientific assumptions about climate change.72, 73
Two degrees Celsius does not sound like much, which is true when it refers to normal daytime temperatures. However, when applied to the global average temperature of the earth, it is comparable to human body temperature, where an increase of two degrees can make the difference between normal well-being and life-threatening illness. In extreme scenarios, average temperature could rise six degrees by the end of the century, and even higher in some regions. At the moment, the global average temperature is about five degrees warmer than at the peak of the last Ice Age, when glaciers in the Northern hemisphere soared hundreds of feet high. An increase in the average global temperature of five or six degrees would portend the beginning of a “Heat Age.”
There is no certainty about what all this additional carbon dioxide will do to the earth. Scientific models are imprecise and not all future changes can be predicted. But, does that give us the liberty to play down the impact that people have on the climate the way that interest groups do, especially in the United States? Believing the climate change skeptics is taking an enormous risk for, if they are wrong, we will face a dangerous, perhaps irreversible situation. If the critics are proven right, little change will occur, except perhaps reasonable investments in environmental protection and renewable energy sources.
Underpinning the arguments of climate change skeptics is an assumption that humans are only a small factor in world events, so negligible that they cannot possibly trigger serious consequences. We shall simply carry on, they say. Advocates of this attitude think little of the Anthropocene idea. However, many scientific findings undermine the argument that human actions are only a trivial factor in earth events. The magnitude of the human factor is shown by one US Geological Survey study, according to which humans emit 135 times more carbon dioxide than all volcanoes combined.74 Axel Kleidon from the Max Planck Institute for Biogeochemistry, in Jena, Germany, states that annual human consumption of free energy stands at approximately 50 terawatts, mainly due to burning fossil fuels and cultivating crops. This is equivalent to between five and ten per cent of free energy available. According to Kleidon, this is significantly more free energy than is produced by all the volcanoes, earthquakes and other tectonic events, combined.75
Population growth, and space and energy requirements
