Cloud feedback is a type of climate change feedback, where the overall cloud frequency, height, and the relative fraction of the different types of clouds are altered due to climate change, and these changes then affect the Earth's energy balance. On their own, clouds are already an important part of the climate system, as they consist of water vapor, which acts as a greenhouse gas and so contributes to warming; at the same time, they are bright and reflective of the Sun, which causes cooling. Clouds at low altitudes have a stronger cooling effect, and those at high altitudes have a stronger warming effect. Altogether, clouds make the Earth cooler than it would have been without them.
During daytime, clouds scatter incoming shortwave radiation from the Sun due to their albedo, which results in substantial cooling
Water vapor in the clouds also absorbs longwave radiation from the Earth's surface and reemits it back. This effect is weaker than the albedo cooling, but it is active day and night
Tropical clouds are known to have a cooling effect, but it is uncertain whether it would become stronger or weaker in the future
Air pollution, including from large-scale land clearing, has substantially increased the presence of aerosols in the atmosphere when compared to the preindustrial background levels. Different types of particles have different effects, and there is a variety of interactions in different atmospheric layers. Overall, they provide cooling, but complexity makes the exact strength of cooling very difficult to estimate.
Climate change feedbacks are processes in the climate system which amplify or diminish the effect of forces that initially cause the warming. Positive feedbacks enhance global warming while negative feedbacks weaken it. Feedbacks are important in the understanding of climate change because they play an important part in determining the sensitivity of the climate to warming forces. Climate forcings and feedbacks together determine how much and how fast the climate changes.
Methane climate feedbacks in natural ecosystems.
Nine probable scenarios of greenhouse gas emissions from permafrost thaw during the 21st century, which show a limited, moderate and intense CO2 and CH4 emission response to low, medium and high-emission Representative Concentration Pathways. The vertical bar uses emissions of selected large countries as a comparison: the right-hand side of the scale shows their cumulative emissions since the start of the Industrial Revolution, while the left-hand side shows each country's cumulative emissions for the rest of the 21st century if they remained unchanged from their 2019 levels.
Global warming caused by the potential disappearance of the four notable ice masses and their albedo, assuming an average warming level of 1.5 °C (2.7 °F) throughout. While mountain glaciers and summer Arctic sea ice can be lost in a century or two, total ice sheet loss requires multiple millennia.
