Query: Unlike the simple example of positive feedback we learned in high school, the increase from every round of feedback gets smaller and smaller, in the case of the enhanced greenhouse effect.

Relevant passages:
Climate change feedback <=SEP=> Climate change feedback is important in the understanding of global warming because feedback processes may amplify or diminish the effect of each climate forcing , and so play an important part in determining the climate sensitivity and future climate state . Feedback in general is the process in which changing one quantity changes a second quantity , and the change in the second quantity in turn changes the first . Positive feedback amplifies the change in the first quantity while negative feedback reduces it .   The term `` forcing '' means a change which may `` push '' the climate system in the direction of warming or cooling . An example of a climate forcing is increased atmospheric concentrations of greenhouse gases . By definition , forcings are external to the climate system while feedbacks are internal ; in essence , feedbacks represent the internal processes of the system . Some feedbacks may act in relative isolation to the rest of the climate system ; others may be tightly coupled ; hence it may be difficult to tell just how much a particular process contributes . Forcings , feedbacks and the dynamics of the climate system determine how much and how fast the climate changes . The main positive feedback in global warming is the tendency of warming to increase the amount of water vapor in the atmosphere , which in turn leads to further warming . The main negative feedback comes from the Stefan -- Boltzmann law , the amount of heat radiated from the Earth into space changes with the fourth power of the temperature of Earth 's surface and atmosphere .   Some observed and potential effects of global warming are positive feedbacks , which contribute directly to further global warming . The Intergovernmental Panel on Climate Change 's ( IPCC ) Fourth Assessment Report states that `` Anthropogenic warming could lead to some effects that are abrupt or irreversible , depending upon the rate and magnitude of the climate change . ''

Positive feedback <=SEP=> Positive feedback is a process that occurs in a feedback loop in which the effects of a small disturbance on a system include an increase in the magnitude of the perturbation .  That is , A produces more of B which in turn produces more of A . In contrast , a system in which the results of a change act to reduce or counteract it has negative feedback . Both concepts play an important role in science and engineering , including biology , chemistry , and cybernetics .   Mathematically , positive feedback is defined as a positive loop gain around a closed loop of cause and effect .  That is , positive feedback is in phase with the input , in the sense that it adds to make the input larger .  Positive feedback tends to cause system instability . When the loop gain is positive and above 1 , there will typically be exponential growth , increasing oscillations , chaotic behavior or other divergences from equilibrium . System parameters will typically accelerate towards extreme values , which may damage or destroy the system , or may end with the system latched into a new stable state . Positive feedback may be controlled by signals in the system being filtered , damped , or limited , or it can be cancelled or reduced by adding negative feedback .   Positive feedback is used in digital electronics to force voltages away from intermediate voltages into ' 0 ' and ' 1 ' states . On the other hand , thermal runaway is a positive feedback that can destroy semiconductor junctions . Positive feedback in chemical reactions can increase the rate of reactions , and in some cases can lead to explosions . Positive feedback in mechanical design causes tipping-point , or ` over-centre ' , mechanisms to snap into position , for example in switches and locking pliers . Out of control , it can cause bridges to collapse . Positive feedback in economic systems can cause boom-then-bust cycles . A familiar example of positive feedback is the loud squealing or howling sound produced by audio feedback in public address systems : the microphone picks up sound from its own loudspeakers , amplifies it , and sends it through the speakers again .

Negative feedback <=SEP=> Negative feedback occurs when some function of the output of a system , process , or mechanism is fed back in a manner that tends to reduce the fluctuations in the output , whether caused by changes in the input or by other disturbances .   Whereas positive feedback tends to lead to instability via exponential growth , oscillation or chaotic behavior , negative feedback generally promotes stability . Negative feedback tends to promote a settling to equilibrium , and reduces the effects of perturbations . Negative feedback loops in which just the right amount of correction is applied with optimum timing can be very stable , accurate , and responsive .   Negative feedback is widely used in mechanical and electronic engineering , but it also occurs naturally within living organisms , and can be seen in many other fields from chemistry and economics to physical systems such as the climate . General negative feedback systems are studied in control systems engineering .