Global Change and the Earth System Quotes

“Virtually all of the discussions on the consequences of global change for human well-being focus on the material and physical aspects of such change – provision of food and water, security of infrastructure, impacts on the economy, and so on. Virtually no analyses consider the psychological impacts or consequences of global change on individual humans and on their societies. Many in the scientific community may consider these aspects to be irrational and inconsequential. Yet, in the final analysis, it will be the human perceptions of global change and the risks associated with it that will determine societal responses. At the heart of these perceptions is the fundamental place of humanity in the natural world.”
― Will Steffen, Global Change and the Earth System: A Planet Under Pressure: Executive Summary

“Coral reefs are a good example of threshold and step-change behaviour. Reefs are subject to a wide variety of natural disturbances, from hurricanes to episodic outbreaks of crown-of-thorns starfish. Over the last several decades human stresses - nutrient and sediment loadings from adjacent coastal areas, fishing and tourism - have begun to interact with natural disturbances to put reefs under increasing stress. Global change is adding even more stresses of a quite different nature. Increasing atmospheric CO2 is changing the carbonate chemistry in the surface waters of the ocean, making it more difficult for reef organisms to form their hard shells. At the same time, warming of the upper ocean is leading to widespread bleaching events. These new, global-scale stresses operate everywhere, and are both persistent and inexorably increasing in severity. Given sufficient pressure from these interacting local to global stresses, coral reefs can cross a threshold with widespread death of the coral and a rapid change to colourless algal beds.”
― Will Steffen, Global Change and the Earth System: A Planet Under Pressure: Executive Summary

“The palaeo-record shows that in the Earth System abrupt changes and surprises are a common feature, and that environmental extremes beyond those recorded during the period of instrumental record occur frequently. Especially large risks to the Earth System are associated with the ‘threshold-abrupt change’ behaviour that arises when a well-buffered system is forced beyond a certain limit. Until the time that the threshold is approached, it appears that the system is unresponsive to the forcing function. However, when the threshold is passed, the system can move to another state very quickly, a state that may prove to be difficult to reverse or may even be irreversible. Changes of this nature are especially dangerous in the context of global change. Societies can have little or no warning that a forcing factor is approaching such a threshold, and by the time that the change in Earth System functioning is observed, it will likely be too late to avert the major change.”
― Will Steffen, Global Change and the Earth System: A Planet Under Pressure: Executive Summary

“The development of the ozone hole was an unforeseen and unintended consequence of widespread use of chlorofluorocarbons as aerosols in spray cans, solvents, refrigerants and as foaming agents. Had, inadvertently, bromofluorocarbons been used instead, the result could have been catastrophic. In terms of function as a refrigerant or insulator, bromofluorocarbons are as effective as chlorofluorocarbons. However, on an atom-for-atom basis, bromine is about 100 times more effective at destroying ozone than is chlorine. As Nobel Laureate Paul Crutzen has written “This brings up the nightmarish thought that if the chemical industry had developed organobromine compounds instead of the CFCs – or, alternatively, if chlorine chemistry would have run more like that of bromine – then without any preparedness, we would have been faced with a catastrophic ozone hole everywhere and at all seasons during the 1970s, probably before the atmospheric chemists had developed the necessary knowledge to identify the problem and the appropriate techniques for the necessary critical measurements. Noting that nobody had given any thought to the atmospheric consequences of the release of Cl or Br before 1974, I can only conclude that mankind has been extremely lucky.” (Source: P. Crutzen (1995) My life with O3, NOx and other YZOxs. Les Prix Nobel (The Nobel Prizes) 1995. Stockholm: Almqvist & Wiksell International. pp. 123-157).”
― Will Steffen, Global Change and the Earth System: A Planet Under Pressure: Executive Summary