CLOUDS
Negative Feedback
What is Negative Feedback in climate system?
Negative climate feedback refers to processes that act to counteract or reduce the impact of an initial change in climate.
Examples of negative feedbacks in relation to climate change include evaporation and cloud formation, as well as blackbody radiation.
Aerosol Affects Earth's cooling effect
Aerosols can influence both directly and indirectly to the Earth’s cooling effect. First, when the sky is clear, aerosols can reflect incoming sunlight back to outer space. This can block some of the energy that would have reached the Earth’s surface, and having a cooling effect on the climate. This mechanism is the direct cooling effects of aerosols. As an indirect effect, aerosols act as a condensation nuclei and the clouds can reflect sunlight and cool the surface of earth.
Aerosols are fine solid or liquid particles in the atmosphere, where they stay for days to weeks before falling to the ground or being washed away by rain or snow. Atmospheric water molecules are drawn to aerosol particles like magnets, and they form water droplets and eventually create a cloud. In other words, aerosols have close relationship with clouds that they help forming clouds.
The Korean Polar Research Institute published a study in June 2021 showing that Arctic microalgae increased by global warming play a role in cooling the Earth's temperature. The matter emitted by microalgae helps make clouds, which blocks sunlight entering the Earth and lowering the global temperature.
To explain the detailed process, a gas component called dimethyl sulfur(DMS) emitted by Arctic microalgae made cloud particles.
At the Zeppelin Earth Atmospheric Monitoring Observatory in Nialson, Norway, the research team observed changes in the concentration of DMS in the air from 2010 to 2019 and then conducted an analysis of the formation process of cloud particles.
As a result, DMS became very small particles and pulled on the surrounding water vapor or other atmospheric materials to grow clouds into particles. In other words, the DMS emitted by microalgae served as a condensation nucleus.
It is said that the increase in microalgae is largely due to global warming. However, the results of this study revealed that the Earth is acting as a self-purification that creates a cooling effect.
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Cloud Formation Effect of Arctic Microalgae
As the surface temperature of the Earth increases there are increased levels of evaporation from the oceans. This increased evaporation results in more clouds forming in the lower atmosphere. These clouds in turn reflect some incident solar radiation back into space, slightly decreasing the surface temperature. Low thick clouds primarily reflect sunlight and cool the surface of the Earth. Low clouds over the ocean have a shorter cover because they increase the reflectivity without affecting the long wave at the atmospheric wall.
Negative feedback of cloud and low thick cloud
The cooling effect of clouds in the mid-latitude area has been found to have an effect on the temperature drop. Amilcare perperato, a professor at Princeton University and HMEI(High Meadows Environmental Institute), Cerasoli, a graduate student, and Jun Ying, an assistant professor at Nanjing University investigated the effects of vegetation on cloud formation in mid-latitude areas. They modeled the interaction between various vegetation and atmospheric boundary layers.
The atmospheric boundary layer is the lowest layer of the atmosphere and directly interacts with the Earth's surface. The modeling was to see if cloud formation was affected by the type of vegetation, and the focus was between 30-45 degrees latitude.
They found that clouds formed more frequently in wooded areas and had a greater cooling effect on the Earth's atmosphere. In the case of the mid-latitude region, they found that the cooling effect of clouds combined with the carbon removal effect is greater than the solar radiation absorbed by the forest region.
In summary, clouds form more frequently in forested areas, which promotes the cooling effect of the Earth's atmosphere. The researchers observed that clouds tend to form early in the afternoon in forest areas, affecting the cooling effect as cloud cover lasts longer and the time the clouds reflect solar radiation from Earth increases.