The Little Things Count

Homeostasis is a dynamic state, in which various regulatory systems maintain a fluctuating but overall balanced, set of conditions. If something happens to change conditions from normal, information is fed back to the regulatory systems and action is taken to rectify the situation. The action to prevent the regulating mechanisms going too far is called negative feedback. Since life began, there has been about a 25% increase in the radiation arriving at Earth from the sun. Despite fluctuations the earths surface has remained relatively constant.
The increase in plant life over the years will have increasingly removed CO2 from the air during photosynthesis. This will have reduced the greenhouse effect.

But the greenhouse effect is increasing due to humans adding CO2 to the atmosphere, this with masses of deforestation upsets the balance, so CO2 is increasing faster than it would if we didn't use wood to build our houses. Hence, the enhanced greenhouse effect.


Negative feedback: A system whereby a change is stopped from going too far by adjustments to reverse it.

An example of negative feedback is when increased global temperatures increase evaporation. This may lead to increased cloud cover that can reflect some of the incoming radiation and reduce temperatures.


Positive Feedback: A system whereby a change produces effects that increase or enhance the change to take the system out of balance.

For example, it has been shown that over the last 10 years, the permafrost (area where material just below the ground surface has been at 0°C for 2years+) in Alaska and Siberia has been melting. The organic material that was beneath the ice is now decomposing and releasing large amounts of Methane into the air. This is a powerful greenhouse gas and is leading to to rises in temperatures, which causes more permafrost to melt.