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Opinion

Copenhagen: A new global deal for sustainable development?

There are nine planetary boundaries that should be respected in order to reduce risking the self-regulating capacity of the planet. The environmental conference is only a first step.

By Johan Rockström / October 19, 2009



Stockholm

Reaching a substantive global agreement in Copenhagen, Denmark, at the UN-sponsored climate-change conference this December on reducing greenhouse-gas emissions is a necessary step, but it is not sufficient. In order to avoid catastrophic tipping points, we need to effectively manage key Earth system processes, and we need to do it now.

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In the run-up to the climate negotiations in Copenhagen, it is easy to get the impression that as long as we reduce emissions of greenhouse gases we will be safe from dangerous, or even disastrous, outcomes for humanity.

But mounting scientific evidence strongly suggests that is very unlikely.

For decades, we have lived with the predominant belief that environmental change occurs in an incremental, linear, and predictable fashion.

But growing evidence indicates that this may be the exception, not the rule, and that long periods of gradual change can eventually push us past thresholds that result in abrupt and potentially disastrous changes.

In fact, we can no longer exclude the possibility that we are crossing hard-wired thresholds at the planetary level, threatening the self-regulating capacity of the planet to remain in the stable and favorable state in which human civilizations and societies have developed during the past 10,000 years.

Compared with the 200,000 years or so that we humans have roamed around on Earth, this Holocene state has been extraordinarily stable from an environmental perspective, providing humanity with the precondition for human development as we know it, from the rise of agriculture to the modern industrial societies of today.

In a recent article presented in the scientific journal Nature, my colleagues and I make a first attempt to identify and quantify the Earth system processes and potential biophysical thresholds that, if crossed, could generate unacceptable environmental change for humanity, such as irreversible loss of inland glaciers, a transition of rain forests to savannas, massive destruction of tropical coral reefs, desertification of current agricultural land, and the shift in the Indian and African monsoon systems.

For each of the processes we identified, we also propose planetary boundaries that should be respected in order to reduce the risk of crossing these thresholds and moving into an undesired state for humanity on Earth.

We identified nine critical Earth system processes including climate change, depletion of stratospheric ozone, land-use change, freshwater use, rate of biological diversity loss, ocean acidification, amounts of nitrogen and phosphorus inputs to the biosphere and oceans, air pollution from aerosol loading, and chemical pollution.

Our scientific proposition, based on this new concept, is that as long as we stay within the boundaries for these nine, we give ourselves a long-term safe operating space for human development on Earth. We thereby stand a good chance of keeping Earth within the stable Holocene state for at least another couple thousand years, providing ample opportunities to support long-term social and economic development in the world.

Climate change is, not surprisingly, one of the nine proposed boundary processes, and here we build on the latest climate science, which indicates that we may have to stabilize the concentration of carbon dioxide in the atmosphere to 350 parts per million (p.p.m.) in order to avoid nonlinear and potentially irreversible environmental change.

We are already at approximately 390 p.p.m., i.e., we are already in a danger zone.

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