SCIENCE
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The carrying capacity of the Earth has been exceeded. Diverse reports suggest
the ecological overshoot is about 25%. [3]
Fossil fuels have permitted levels of resource extraction and waste that mask the general underlying level of ecological degradation. The loss of 30% of arable land and soil fertility that has occurred since 1950 has been masked by artificial fertilizers made from natural gas. Although 90% of all large fish species are at risk of extinction, fossil fuel-powered fleets can fish ever farther from home. The rapidly depleting water tables of India and China are masked by water pumped from tens of millions of deeper wells. Moreover, the case of Peak Oil confirms that our ‘one-time inheritance’ of fossil fuels has begun to decline. The extent of ecosystems destruction is about to be unmasked.
The assumption that human population will continue to grow during this century will be tested by unprecedented circumstances. For example, the population model above demonstrates what may happen if environmental carrying capacity diminishes 40% over the century, and cannot be further masked by declining fossil fuels. Such a future world would have accumulated global habitat loss, hostile climatic changes and loss of coastlines to rising sea levels. Our population might not increase beyond about 2020, and could decline thereafter.
Tipping elements and tipping points.
The IPCC reports give the impression that climate change is a smooth linear transition. However there are large-scale tipping elements in the Earth's climate system that can be switched by small perturbations into a completely different state. A tipping point is a critical feature where such a state transition is triggered. [5]
Fifty-five million years ago, there was a global warming spike at what is now called the Paleocene-Eocene Thermal Maximum (PETM). This is the closest analogue we have to current human impacts on the climate system. The amount of fossil carbon released was similar to contemporary fossil fuel reserves. It probably came from frozen methane hydrates under the ocean sediments. At the equator, temperatures rose 4–5C and at the poles they rose 8–10C. The ocean acidified and dissolved carbonate sediments. The biosphere took tens of thousands of years to recover. Frozen methane was the tipping element at that time. A tipping element with a close threshold is the irreversible melting of the Greenland Ice Sheet. If there is Arctic warming of about 3C, the ice sheet will shrink dramatically, generating further warming in a positive feedback loop. The final sea-level rise from this source alone would be 7 metres, over 2-3 centuries.
Climatologist James Hansen of NASA states that we must dramatically reduce the use of fossil fuels within a decade, or the climate system will be propelled past a tipping point, beyond which it will be impossible to avoid catastrophe. Global warming of 2-3C would give rise to a planet without Arctic sea ice and sea-level rises between 5 and 25 metres. there would be super-droughts in the American West, Southern Europe, the Middle East, and Africa. Further hostile positive feedbacks, such as the melting of frozen Arctic methane or the conversion of the Amazon rainforest to a savannah would be triggered. There is no conceivable policy or management approach that could reverse global warming at such a point. Hansen states, ‘We have to be smart enough to understand what is happening early on.’ [6]
These risks need to be fully understood and honestly integrated into a new global climate treaty. They require no less than a collective, focused response, comparable to a full wartime mobilization and redirection of our industrial base. We have a window of choice and opportunity. We can heed the scientific projections and plan how to handle this climate-energy emergency.
2. Dalai Lama XIV [2007] Collected Statements on Environment
3. www.footprintnetwork.org
4. www.theoildrum.com World Energy & Population Trends to 2100
5. Lenton T. Tipping Points in the Earth System
6. Spratt D. & Sutton P. [2008] Climate Code Red