The world has recently demonstrated an awareness of itself as a single economic system. Following the collapse of the US housing market over the last year and a half, the central banks of Asia, Europe and North America co-ordinated the launching of the largest fiscal aid packages in human history. Most economists agree that they thus averted the collapse of the world banking system and major depressions in the economies of developed and developing nations.
So why is it so much more difficult for the world to see itself as a single natural system? As British Ambassador Simon Gass pointed out in impeccable Greek last week to an economic crisis conference, fixing the environment is going to be much harder than fixing the economy. Yet that is the task now facing scientists and policymakers at the penultimate global summit on climate change before a successor treaty to the Kyoto Protocol is to be signed. The summit takes place in Poznan, Poland on December 1-12.
The difficulty arises partly from the fact that developing economies such as China and India want a grace period the Earth can ill afford them, to reach living standard parity with Western nations that caused much of today's pollution getting where they are. While the argument hinges on justice for the many, it disguises a deeper motive - a race to supplant the waning economic power of the United States on the world stage.
The greater difficulty is in the nature of the problem: while the human-created economy goes in circles and retrogradations of optimism and contraction, the human effect on the atmosphere is consistently detrimental. To reverse it we must either suffer a rapid population decline, or abandon our growth-based economic development which eats up primary resources to create wealth as we understand it. The choice seems a rum one: get poorer or die - possibly both. Since no global summit can convene on the basis of that choice, the only option in Poznan is reform of our way of life.
How is this to be done? Our carbon-intensity goes much deeper than driving cars and consuming manufactured goods that take energy to produce and run. It extends to the way we grow our food.
While we were hunter-gatherers and few in number, the earth's carbon cycle was mostly in surplus, so to speak. Through photosynthesis and decomposition, plants tucked back into the ground as much carbon as humans, animals, wildfires and volcanoes were able to release. Measurements taken from air bubbles trapped in glacial ice show that atmospheric carbon dioxide reversed a falling trend approximately 8,000 years ago, and methane 5,000 years ago. In a Scientific American article published in March 2005, palaeoclimatologist William F Ruddiman from the University of Virginia suggested that the first was due to the clearing of forests for agriculture in Europe, and the second due to flooding of rice fields in China.
But those levels of carbon dioxide and methane skyrocketed in the last 150 years with the large-scale burning of coal during the Industrial Revolution, followed by oil in the 20th century. Pre-industrial levels of CO2, estimated at 280 parts per million, have now reached 385 parts per million and are rising.
The first results are visible. Ice shelves that have existed since before the last Ice Age ended about 12,000 years ago are deteriorating in West Antarctica, Greenland and the Arctic. Scientists visiting the Ilulissat glacier in Greenland during the summer of 2007 declared the UN's climate change model obsolete. Some predicted the collapse of the Arctic icecap, originally estimated for 2100, by 2030.
We are therefore on a downward spiral that we have not been able to stop, let alone reverse. The question now arises whether that spiral can produce points of no return. The World Wide Fund for Nature suggests that three degrees of warming would be one such tipping point, leading to total destruction of most ice shelves. Another is the destruction of the Amazon rainforest, the world's largest lung on land.
The most frightening tipping point, perhaps, is the prospect of Arctic permafrost in Russia and Canada melting to release methane now trapped in peat bogs - a gas 25 times more effective than CO2 in helping the earth absorb heat.
Other tipping points are detrimental to biodiversity - particularly in marine life. The oceans have now absorbed enough CO2 to mark an increase in their acidity. That makes it harder for calcifying marine organisms such as coral reefs, zooplankton and snails to produce the shell on which their life depends. These creatures either sit at the bottom of the food chain or create habitats for food chains. Their endangerment has enormous implications for biodiversity throughout the marine ecosystem.
Another possible biodiversity tipping point for the oceans is the disruption of ocean currents that circulate warm water to the poles and cold water to the equator. Should enough sea ice melt all at once, the rhythm might be broken, argues Tim Lenton from the University of East Anglia, devastating both warm and cold ecosystems.
Scientists have long warned that creatures are becoming extinct at a rate between 100 and 1,000 times the background rate. To the best of our knowledge, we are losing plants and animals at the highest rate seen since the disappearance of the dinosaurs 65 million years ago.
The question that arises for at least some of mankind is existential. But for most of us it is undeniably one of quality of life. We face the emperor's dilemma in the Hans Christian Andersen story - to tinker forlornly with a broken machine or to enjoy the company of a nightingale. Those who argue that environmental concerns run counter to a healthy economy may rail against environmental regulations, but they can never argue with spontaneous shifts in desire, or they would have to renounce belief in the golden rule of capitalism: that supply will always meet demand.
Having become the dominant force in evolution, what kind of planet do we demand for our children?