Planetary boundaries

Planetary boundaries is a concept involving Earth System processes which contain environmental boundaries, proposed in 2009 by a group of Earth system and environmental scientists led by Johan Rockström from the Stockholm Resilience Centre and Will Steffen from the Australian National University. The group wanted to define a 'safe operating space for humanity' for the international community, including governments at all levels, international organizations, civil society, the scientific community and the private sector, as a precondition for sustainable development. The framework is based on scientific evidence that human actions since the Industrial Revolution have become the main driver of global environmental change. According to the paradigm, 'transgressing one or more planetary boundaries may be deleterious or even catastrophic due to the risk of crossing thresholds that will trigger non-linear, abrupt environmental change within continental-to planetary-scale systems.' The Earth system process boundaries mark the safe zone for the planet to the extent that they are not crossed. As of 2009, two boundaries have already been crossed, while others are in imminent danger of being crossed. In 2009, a group of Earth System and environmental scientists led by Johan Rockström from the Stockholm Resilience Centre and Will Steffen from the Australian National University collaborated with 26 leading academics, including Nobel laureate Paul Crutzen, Goddard Institute for Space Studies climate scientist James Hansen and the German Chancellor's chief climate adviser Hans Joachim Schellnhuber and identified nine 'planetary life support systems' essential for human survival, attempting to quantify how far seven of these systems had been pushed already. They estimated how much further humans can go before planetary habitability is threatened. Estimates indicated that three of these boundaries—climate change, biodiversity loss, and the biogeochemical flow boundary—appear to have been crossed. The boundaries were 'rough, first estimates only, surrounded by large uncertainties and knowledge gaps' which interact in complex ways that are not yet well understood. Boundaries were defined to help define a 'safe space for human development', which was an improvement on approaches aiming at minimizing human impacts on the planet. The 2009 report was presented to the General Assembly of the Club of Rome in Amsterdam. An edited summary of the report was published as the featured article in a special 2009 edition of Nature. alongside invited critical commentary from leading academics like Nobel laureate Mario J. Molina and biologist Cristián Samper. In 2015, a second paper was published in Science to update the Planetary Boundaries concept including regional boundaries and findings were presented at the World Economic Forum in Davos, January 2015. A 2018 study, co-authored by Rockström, calls into question the international agreement to limit warming to 2 degrees above pre-industrial temperatures set forth in the Paris Agreement. The scientists raise the possibility that even if greenhouse gas emissions are substantially reduced to limit warming to 2 degrees, that might be the 'threshold' at which self-reinforcing climate feedbacks add additional warming until the climate system stabilizes in a hothouse climate state. This would make parts of the world uninhabitable, raise sea levels by up to 60 metres (200 ft), and raise temperatures by 4–5 °C (7.2–9.0 °F) to levels that are higher than any interglacial period in the past 1.2 million years. Rockström notes that whether this would occur 'is one of the most existential questions in science.' Study author Katherine Richardson stresses, 'We note that the Earth has never in its history had a quasi-stable state that is around 2 °C warmer than the preindustrial and suggest that there is substantial risk that the system, itself, will ‘want’ to continue warming because of all of these other processes – even if we stop emissions. This implies not only reducing emissions but much more.” The idea that our planet has limits, including the burden placed upon it by human activities, has been around for some time. In 1972, The Limits to Growth was published. It presented a model in which five variables: world population, industrialization, pollution, food production, and resources depletion, are examined, and considered to grow exponentially, whereas the ability of technology to increase resources availability is only linear. Subsequently, the report was widely dismissed, particularly by economists and businessmen, and it has often been claimed that history has proved the projections to be incorrect. In 2008, Graham Turner from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) published 'A comparison of The Limits to Growth with thirty years of reality'. Turner found that the observed historical data from 1970 to 2000 closely matches the simulated results of the 'standard run' limits of growth model for almost all the outputs reported. 'The comparison is well within uncertainty bounds of nearly all the data in terms of both magnitude and the trends over time.' Turner also examined a number of reports, particularly by economists, which over the years have purported to discredit the limits-to-growth model. Turner says these reports are flawed, and reflect misunderstandings about the model. In 2010, Nørgård, Peet and Ragnarsdóttir called the book a 'pioneering report', and said that it 'has withstood the test of time and, indeed, has only become more relevant.' Our Common Future was published in 1987 by United Nations' World Commission on Environment and Development. It tried to recapture the spirit of the Stockholm Conference. Its aim was to interlock the concepts of development and environment for future political discussions. It introduced the famous definition for sustainable development: Of a different kind is the approach made by James Lovelock. In the 1970s he and microbiologist Lynn Margulis presented the Gaia theory or hypothesis, that states that all organisms and their inorganic surroundings on Earth are integrated into a single self-regulating system. The system has the ability to react to perturbations or deviations, much like a living organism adjusts its regulation mechanisms to accommodate environmental changes such as temperature (homeostasis). Nevertheless, this capacity has limits. For instance, when a living organism is subjected to a temperature that is lower or higher than its living range, it can perish because its regulating mechanism cannot make the necessary adjustments. Similarly the Earth may not be able to react to large deviations in critical parameters. In his book The Revenge of Gaia, he affirms that the destruction of rainforests and biodiversity, compounded with the increase of greenhouse gases made by humans, is producing global warming.