Climate feedback Mechanisms are processes that can either intensify or weaken the effects of climate forcings. A feedback that increases the warming is a positive feedback and conversely, a feedback that reduces the warming is the negative one.
Positive Feedback
Positive climate feedback are processes where initial changes in the climate system cause secondary changes which in turn increases the effects of the initial change. Positive feedbacks intensify and accelerate climate change because they increase the warming. Here are some examples of a positive feedback:
· Ice-Albedo Mechanism – Ice, due to its clear and white color, is highly reflective which means it has a high albedo. Melting of ice specifically sea ice, corresponds to a decrease in albedo. High reflectivity of ice prevents sunlight from being absorbed which means ice absorbs less solar energy. However, when ice melts, the water beneath it, the soil, and vegetation gets exposed. These surfaces have lower albedo than ice so they absorb more solar radiation. This absorption further warms the temperature which causes even more ice melting and more heating.
· Water Vapor Release – Human activities like burning of fossil fuels that causes release of greenhouse gases into the atmosphere is one of the initial causes of climate change. These gases trap heat in the atmosphere which increases the global temperature. The warmer temperature results to more evaporation on the surface of the earth. The evaporation then results to more water vapor in the atmosphere, which in turn causes even more warming, creating a cycle of heating.
· Carbon Release – Permafrost is a frozen layer of ground on or under the Earth’s surface which contains large amount of carbon found in frozen soil. As the temperature of the Earth increases, this permafrost begins to melt. The melting of this permafrost releases methane into the atmosphere, which is a greenhouse gas. The release of greenhouse gases into the atmosphere will cause more warming which will cause again the melting of permafrost.
· Ocean Warming – Oceans absorb carbon dioxide, which is an important sink for the gas. When concentrations of carbon dioxide increases, the temperature of the Earth’s atmosphere also increases. When that happens, it will also warm the ocean. The increase in temperature of the ocean decreases its ability to remove carbon dioxide from the atmosphere. Hence, it will result to more warming of the Earth’s atmosphere.
Negative Feedback
Negative climate feedback are processes that decrease the intensity of the initial changes. Unlike positive feedback, the initial change causes a second change that reduce the impacts or effects of the said initial change. The negative feedback may sound not a good thing but it maintains the stability of the climate system. Here are some examples:
· Evaporation and Clouds – Despite the global temperature increase due to human activities, there can still be negative feedbacks. As the surface temperature increases, increased levels of evaporation from the ocean also occurs. This results in more cloud formation in the lower atmosphere. These clouds will then reflect some solar radiation back into space, which decreases the surface temperature of the Earth.
· Blackbody Radiation – The Earth is considered a blackbody. As the Earth’s temperature increases, the Stefan-Boltzmann Law states that the emission of infrared radiation back into space also increases. Because of this relationship, there is a slight cooling effect in the surface temperature.
· Weathering – Weathering is a process when rocks exposed at the surface undergo chemical and physical changes due to their interaction with water and atmosphere. Chemical weathering involves consumption of carbonic acid when dissolving minerals in rocks, and thus a sink for carbon dioxide which is a greenhouse gas. When carbon dioxide is removed from the atmosphere, it weakens the greenhouse effect and results to cooling. This weathering occurs more quickly in hotter climates, which have more levels of carbon dioxide. As the warming increases, more weathering will occur in which it will consume more carbon dioxide and thus leads to more cooling of the Earth.
References:
Feedback Mechanisms. (n.d.). Retrieved May 19, 2021, from Earth in the Future: https://www.e-education.psu.edu/earth103/node/668#:~:text=Weathering%20Feedback,physical%20changes%20we%20call%20weathering.&text=If%20you%20remove%20carbon%20dioxide,to%20cooling%20of%20the%20Earth.
Feedback Mechanisms In Climate. (n.d.). Retrieved May 19, 2021, from https://globalchange.umich.edu/globalchange1/current/lectures/Perry_Samson_lectures/feedback_mechanisms/
Kailyn Stenhouse, Maddy Strange, Jason Donev. (2020, April 28). Negative climate feedback. Retrieved May 19, 2021, from Energy Education: https://energyeducation.ca/encyclopedia/Negative_climate_feedback#:~:text=Negative%20climate%20feedback%20is%20any,severity%20of%20some%20initial%20change.&text=This%20is%20a%20negative%20feedback,back%20to%20its%20original%20state.
Kailyn Stenhouse, Maddy Strange, Jason Donev. (2020, April 28). Positive climate feedback. Retrieved May 19, 2021, from Energy Education: https://energyeducation.ca/encyclopedia/Positive_climate_feedback#:~:text=Positive%20climate%20feedback%20is%20a,essentially%20magnifying%20the%20initial%20effect.
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