section_path: Causes of recent global temperature rise/Other factors/Climate change feedbacks
section_name: Climate change feedbacks
paragraph_text: Climate change feedbacks
  
  The response of the climate system to an initial forcing is modified by feedbacks: increased by "self-reinforcing" or "positive" feedbacks and reduced by "balancing" or "negative" feedbacks. The main reinforcing feedbacks are the water-vapour feedback, the ice–albedo feedback, and the net effect of clouds. The primary balancing mechanism is radiative cooling, as Earth's surface gives off more heat to space in response to rising temperature. In addition to temperature feedbacks, there are feedbacks in the carbon cycle, such as the fertilizing effect of CO on plant growth. Feedbacks are expected to trend in a positive direction as greenhouse gas emissions continue, raising climate sensitivity.
  
  Radiative feedbacks are physical processes that influence the rate of global warming in response to warming. For instance, warmer air can hold more moisture, and water vapour itself is a potent greenhouse gas. Warmer air can also result in clouds becoming higher and thinner, where they act as an insulator and warm the planet. Another major feedback is the reduction of snow cover and sea ice in the Arctic, reducing the reflectivity of the Earth's surface there and contributing to amplification of Arctic temperature changes. Arctic amplification is also thawing permafrost, which releases methane and CO into the atmosphere.
  
  Around half of human-caused CO emissions have been absorbed by land plants and by the oceans. This fraction is not static and if future CO emissions decrease, the Earth will be able to absorb up to around 70%. If they increase substantially, it'll still absorb more carbon than now, but the overall fraction will decrease to below 40%. This is because climate change increases droughts and heat waves that eventually inhibit plant growth on land, and soils will release more carbon from dead plants when they are warmer. The rate at which oceans absorb atmospheric carbon will be lowered as they become more acidic and experience changes in thermohaline circulation and phytoplankton distribution. Uncertainty over feedbacks, particularly cloud cover, is the major reason why different climate models project different magnitudes of warming for a given amount of emissions.