Climate feedback loops are processes that either amplify or diminish the effects of climate factors. Essentially, they make the impacts of key climate factors stronger or weaker, starting a chain reaction that repeats again and again.
What is a Feedback Loop?
There are negative and positive climate feedback loops. A positive feedback loop accelerates a temperature rise, while a negative feedback loop decelerates it.
There are a number of positive feedback loops in the climate system. An example is melting ice. Because ice is light-coloured and reflective, much of the sunlight that hits it bounces back into space, which limits the amount of warming it causes. However, as the planet gets hotter, ice melts, revealing the darker-coloured land or water below. This results in more of the sun’s energy being absorbed, leading to more warming, which leads to more ice melting- and so on.
An example of a negative feedback loop is if the increase in temperature increases the amount of cloud cover. The increased cloud thickness or amount could reduce incoming solar radiation and limit warming. However, it is not clear, if additional cloud cover occurs, at what latitudes and at what times it might occur. It’s also not clear what types of clouds might be created- thick low clouds would have a stronger ability to block sunlight than extensive high (cirrus) type clouds.
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Earth’s Own Feedback Loop
Other climate feedback loops are discussed below:
- Clouds– clouds reflect about one-third of the total amount of sunlight that hits the Earth’s atmosphere back into space. Even small changes in cloud amount, location and type could have negative consequences. As mentioned above, a warmer climate could cause more water to be held in the atmosphere, leading to an increase in cloudiness and altering the amount of sunlight that reaches the surface of the Earth. Less heat would get absorbed, which could slow the increased warming.
- Precipitation– precipitation will generally increase due to the increased amount of water held in a warmer atmosphere, but not everywhere- some regions may dry out instead. Changes in precipitation patterns, such as increased water availability, may cause an increase in plant growth, which in turn could potentially remove more carbon dioxide from the atmosphere.
- Greening of the forests– natural processes like tree growth, remove about half of human carbon dioxide emissions from the atmosphere each year. However, the ability of the oceans or forests to continue absorbing carbon dioxide may decline as the world warms, leading to faster accumulation in the atmosphere.
Negative feedback loops are vital in the global climate system. Without the regulating action of the negative feedback loop, a positive loop can spiral out of control, creating irreversible changes in the climate system. This is called a “tipping point.”
Some examples of tipping points are discussed below:
- Ocean circulation– As Arctic sea ice and the Greenland ice sheet melt, ocean circulation in the Atlantic may divert the Gulf Stream, which would significantly change regional weather patterns. A change in the Gulf Stream could lead to a significant cooling in Western Europe.
- Ice loss– If enough ice melts, causing Earth’s surface to absorb more and more heat, then we may hit a point of no return as shrinking ice sheets contribute to sea level rise.
- Methane release– Frozen methane and carbon dioxide lie beneath permafrost in Arctic regions. About a quarter of the Northern hemisphere is covered by permafrost. As the environment warms and the permafrost thaws, these deposits can be released into the atmosphere and present a risk of enhanced warming.
Feedback loops such as these are complex in themselves and even more complex when considered as part of an integrated global climate system. Some are already at work, while others have yet to kick in. Others still – both positive and negative – may yet be discovered.
Featured image by: Sravanthi Simhadri