Climate change and Feedback Mechanism

Climate change refers to the ling term shifts in temperatures and weather patterns. Such shifts can be natural, due to changes in the sun’s activity or large volcanic eruptions. But in recent years (1800 onwards) human activities have been the main driver of climate change due to burning of fossil fuels like coal, oil and gas and releasing of CFC’s.

The Term feedback is similar to the cause and effect loop.

Human example : If the temperature of body is high (the cause) , the body sweats (the effect) in order to cool down. Since the process of sweating is opposing the cause it is called as “negative feedback effect”.

Types of Climatic Feedbacks :

Feedback loops come in two favors : Positive & Negative . The Positive and Negative doesn’t indicate weather a change is good or bad.

• A negative feedback mechanism reduces the effect of change (reinforce) and helps maintain balance.
• A positive feedback mechanism increases the effect of change and produces instability.

In general case the above definition is used but In Climate change few researches can be different. “In climate change it is related to the speed up or slows down a warming trend. A Positive feedback accelerates a temperature rise whereas a negative feedback slows it down.“

Positive Feedback Examples :-

1. Snow-albedo feedback :
   • In the case of an increase in the global surface air temperature might cause snow and ice to melt in the cold areas. This melting would reduce the albedo of the melting would reduce the albedo of the surface, allowing more solar energy to reach the surface which would further rise the temperature.
   • In the case of an reduce in temperature in the global surface air temperature might cause snow to increase in the area. This increase would increase the albedo of the area that leads to decrease the solar energy to interact with surface causing the further decrease the temperature. ( a runaway ice age ).
2. Vapor-greenhouse / vapor-temperature feedback
   • Over the years temperature is rising slowly which cause the oceanic evaporate faster and increase in the quantity of water vapor. The increased quantity of water vapor absorbs more of the Earth’s infrared radiation, thus strengthening atmospheric greenhouse effect. This strengthening causes further rise in temperature. If this feedback remains unchecked the earth’s temperature would increase until the oceans evaporates completely. (Such a reaction is called a runaway greenhouse effect).
   • Opposite to the above effect can cause global cooling.
3. Ocean warming
   • The oceans are important sink for CO₂ through absorption of the gas into the surface water. As CO₂ increases, it increase the warming potential of atmosphere, if air temperature rises, it leads to the increase in ocean temperature and reduce the absorption potential of CO₂. (The ability of removal of CO₂ from atmosphere decreases with increase in temperature). This increase in CO₂ in atmosphere could have intensify the further increase in CO₂, and leads to a positive feedback effect.

Negative Feedback Examples :-

1. Weathering feedback effect
   • Rock exposed at the surface interacts with water and causes various physical and chemical changes leads to weathering. The chemical weathering most often involves the consumption of carbonic acid. This process is a sink for atmospheric CO₂ , which is an important green house gas. This leads to cooling of the Earth.
     • Now consider some warming occurs, this encourages the weathering. This leads to consume more CO₂ Which leads to decrease the GHG and cooling favors.
2. Cloud feedback Effect
   • As Increase in surface temperature increase the ocean to warm and cause more number of low level clouds. These low level of cloudiness reflects a large percentage of incoming solar radiation, and with less solar energy is available to heat the surface leads to cool down the surface.
3. Earth albedo feedback effect
   • As the surface warms, it emits more infrared radiation. This increase in radiant energy from the surface would greatly slows down the rise in temperature and helps to stabilize the climate. It is the strongest negative feedback in climate system and greatly lowers the possibility of a runaway greenhouse effect.