Population Surge: "10 Billion" - Stephen Emmott speaking at The Royal Court Theatre in London.

There has been a highly successful run at the Royal Court Theatre, in London, not of a play in the usual form, but of a lecture by Professor Stephen Emmott, who leads Microsoft's Computational Science Laboratory in Cambridge and is Professor of Computational Science at Oxford University. The title, "10 Billion" refers to the human population which it is thought may rise to this number by the end of the present century, with back-breaking pressure on the available resources of the Earth: principally those of food, freshwater, and energy. I attended its final performance last Saturday.

Since the inevitable outcome of consumption is excretion, by that time, we will be drowning in our own waste, particularly carbon, such that many lands including Bangladesh will be inundated. The global temperature rise, too, is thought not to be a mere 2 degrees C by the end of the century but 6 degrees, making life on earth, as Emmott describes it "a living hell."

Emmott describes himself as a "rational pessimist" and while his delivery is tinged with ironic humour, it is mostly deadpan, rendering the sheer facts and figures both compelling and convincing. I was at one time skeptical about global warming and its consequences, but now there seems to me little room for doubt that humanity is in a severe predicament, both from the aspect of resource depletion and treating the planet like a giant landfill tip.

Emmott points out that we are using all of the arable land available to us, as a population of 7 billion, and that to feed 10 billion will require clearing forested land, including rainforests which have been described as the "lungs of the earth".

Of all resources, that most critically threatened is water, and it is staggering the quantities of "hidden water" that are used to provide some very commonplace items. For example, it takes 3,000 litres of water to produce a beefburger, and in Britain some 10 billion burgers are consumed per year, therefore necessitating the consumption of 30 trillion litres, or 30 cubic kilometers (km^3) of water.

It takes 27,000 litres of water to produce one bar of chocolate.

100 litres of water are used to make one cup of coffee.

It takes 4 litres of water to make one one litre plastic bottle of water... that's before the water is put into it.

At a population of 7 billion, our energy consumption amounts to around 16 TW, and this will need to rise to 20 TW to provide for the eponymous "10 billion". Since we are highly dependent on fossil fuels, oil, gas and coal, which provide around 87% of the total energy used by humans on earth, our greenhouse gas emissions will almost certainly have to rise, given the limitations of renewable energy sources.

30% of greenhouse gas emissions originate from food production, which is more than from transportation or manufacturing.

To meet that 20 TW of energy, while avoiding burning carbon at an accelerated rate. would require building 960 new hydroelectric dams, each the size of the Three Gorges Dam which spans the Yangtze River in China, PLUS 15,000 NEW nuclear power plants. In terms of uranium fuel resources alone this does not seem very realistic, let alone making sufficient concrete (a hugely CO2 emitting process) for both dams and NPPs.

It is expected that demand for food will double by 2050. This not only reflects the rise in population per se, but that more affluent people eat more food, and the consumer society is expected to expand within that number.

Emmott gave two choices: to "technologise" our way out of trouble, but concluded this was unlikely to be possible and the other option was to "change our behaviour", by consuming less food, less water, and less "stuff". Surplus cash for "stuff" arose when food became cheap in consequence of the Green Revolution. Food prices are rising significantly, and the current US drought could have a drastic effect on world grain availability, with consequences across the world. A drought in Russia recently meant that some 40% of an expected 100 million tonnes of wheat was not produced. Russia held onto supplies to feed its own people which led to food shortages and riots in the far east, India and Pakistan. Emmott speculates, "imagine if that same proportion of the 400 million tonne US wheat output was lost"... indeed, the outcome would be catastrophic.

He is less than sanguine that humans will change their behaviour, believing that developing nations will still aspire to a western lifestyle, whereas the reality is that in the west we need to consume less while more than one billion people in the non-legacy nations, who are malnourished, need to consume more. And the outcome of this? As he puts it, "We're fucked", and I suspect he may well be right.

Apparently, species on Earth are becoming extinct at a rate one thousand times faster than the normal evolutionary rate as we consume the planet's resources.

In 1960, there were 100 billion air-miles flown. In 1980 this had risen to 1,000 billion air-miles and now it is 6,000 billion.

Emmott draws the analogy that if it were known that an asteroid was on its way and would hit the Earth in the year 2094, say, Astronomy and Physics being "simple subjects" would allow a precise prediction of the date and moment of impact and where exactly on Earth it would strike. He says that in such a case, the entire world would mobilise its resources, (1) to mitigate the damage and loss of life from the impact itself, and (2) to inaugurate the most effective procedures for how to cope in its aftermath. Although the likely number of casualties may well be of the same order, the threat to humans is not an external source, like an asteroid, but it is ourselves and our behaviour and yet we do nothing.

What however is the likelihood that the world human population will rise to 10 billion. According to UN's 2010 revision of its population projections, it will peak at 10.1bn in 2100. Some experts dispute the UN's forecast and have argued that birthrates will fall below replacement rate in the 2020s. According to these forecasters, population growth will be only sustained till the 2040s by rising longevity but will peak below 9bn by 2050.

That noted, a worst case scenario predicts that the world population will peak at 7.1 billion in 2024, and then fall to 2.5 billion (close to the estimated carrying capacity of the planet) by 2100. The latter assumes nothing and is a simple mathematical curve-fit of a logistic (population growth) function to actual population data. Is this a mathematical artefact or a simple reflection of a population with limited resources, like the behaviour of bacteria growing on nutrient agar in a Petri dish? Only time will tell, but the "10 Billion" problem may never arise, let alone 16 billion by the end of the century. We are an overshoot species, and may expect a rapid cull, as in the S-shaped curve that prevails for bacteria. The initial growth is slow, but then given sufficient resources (food - oil, and gas in the human situation), the population rapidly escalates until it can no longer be sustained by its food. Then the bacteria begin to starve and consume each other.