The Consequences of Nonlinearities in the Earth’s Climate System

In 2003 an article was published in Global Change Newsletter by R.A. Pielke Sr., H.J. Schellnhuber, and D. Sahagian entitled “Non-linearities in the Earth system”.

Excerpts from this article read,

“Research to-date has revealed the need to establish the limits to predictability within the Earth System. It has been shown that climate prediction needs to be treated as an initial value problem with chaotic behaviour. This perspective acknowledges that beyond some time period, our ability to provide reliable quantitative and detailed projections of climate must deteriorate to a level that no longer provides useful information to policymakers.”

The significance of this message has still has not been recognized, as exemplified by the NCAR press release of October 19, 2006 of entitled “Expect a Warmer, Wetter World this Century” which is based exclusively on multi-decadal global climate predictions (the issue of publishing climate predictions as forecasts in peer reviewed journals is a topic we will pursue in depth in a later weblog; we certainly do not publish weather forecasts before the event occurs in a peer reviewed journal!).

In our Global Change newsletter article we advocate for a different approach to environmental risk assessment that does not rely on prediction as the main tool. We write

“Even in the absence of the ability to provide skilful forecasts, there is, however, a critical societal need to identify parts of the Earth System that are particularly vulnerable to environmental variability. As such, the assessment of certain critical components – in the context of the overall non-linear system, may be useful. For example, one critical issue is water resource development, because it is influenced by environmental variability and change, and because it alters the climate system through irrigation, impoundment, draining of wetlands, and deforestation. Such “hot spotsâ€? of Earth System vulnerability need to be identified and monitored so that their non-linear interactions with the rest of the Earth System can be understood in support of policy, strategic land use practices, and general water resource planning.”

Comprehensive vulnerability assessments need to be applied to reduce the societal risk to future environmental conditions, regardless of their cause. This approach should be adopted as the scientific framework to communicate to policymakers, rather than continuing to focus on multi-decadal global climate predictions, which as our article states,

” beyond some time period…. [the] ability to provide reliable quantitative and detailed projections of climate must deteriorate to a level that no longer provides useful information to policymakers.”

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Filed under Climate Models, Vulnerability Paradigm

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