feedback and climate as a system of response and reaction

Technically speaking, feedback is a fundamental trait of living systems and is used to describe the character of a two sided relationship among equal forces or equally engaged participants.

Any dynamic process is characterized by feedback, or: the reciprocal means by which change is induced.

Change in the sense of feedback is induced for self-regulation, which occurs only as responses either reinforce or alter the initial conditions of existence.

types

Reinforcement or alteration of initial conditions, or state of existence is described by the concept of feedback.

Types of feedback	initial status	subsequent status
positive (+)	reinforced	enhances initial conditions
negative (-)	countered	alters the initial conditions

Both of the above types of feedback are needed for anything to live or for any process to be regulated by either external or internal factors.

When something living is regulated by internal factors responding to external stimuli we refer to the outcome as homeostasis.

When the external conditions are altered and regulated by a set of physical conditions inherent in the external world, we refer to the outcome as a dynamic equilibrium.

climate

Take for example climate change.

examples of feedback and drivers of climate

The atmospheric lifetime of key elemental compounds are:

ingredient	symbol	lifetime
carbon dioxide	CO2	100 years
methane	CH4	12 years
nitrous oxide	NO2	114 years

The atmospheric lifetime means these compounds actively trap long-wave radiation in the atmosphree or oceasn for that extent of time after they are emitted into the air or water.

The atmospheric lifetime is used to characterize the decay of an instanenous pulse input to the atmosphere, and can be likened to the time it takes that pulse input to decay to 0.368 (l/e) of its original value. The analogy would be strictly correct if every gas decayed according to a simple expotential curve, which is seldom the case. For example, CH4 is removed from the atmosphere by a single process, oxidation by the hydroxyl radical (OH), but the effect of an increase in atmospheric concentration of CH4 is to reduce the OH concentration, which, in turn, reduces destruction of the additional methane, effectively lengthening its atmospheric lifetime. An opposite kind of feedback may shorten the atmospheric lifetime of N2O (IPCC 2007, Section 2.10.3). For CO2 the specification of an atmospheric lifetime is complicated by the numerous removal processes involved, which necessitate complex modeling of the decay curve. Because the decay curve depends on the model used and the assumptions incorporated therein, it is difficult to specify an exact atmospheric lifetime for CO2. Accepted values range around 100 years.

types | climate