Disabled Javascript!  

Science Library.info

 You are reading this message because you have attempted to access a page on www.umwelt.science which requires Javascript to be enabled.

Javascript is an essential tool for much functionality on the internet, and is perfectly safe to use, since modern browsers prevent abusive use. If you have it disabled, you will not be able to run any interactive software.

You can enable it from the menubar of your browser, following these instructions: Instructions for enabling Javascript on different Browsers

Environment Forum

Latest Posts

Feedback mechanisms

Posted by Cindy Smith Sunday, 22nd January 2017

In climate change there are secondary effects not directly caused by human activities. Do they help or make global warming worse?

Posted by Andrew Bone Sunday, 22nd January 2017

Feedback mechanisms in climate change theory are mechanisms which are secondary effects of direct anthropogenic changes to the Earth's biospheric conditions. There are both positive and negative feedback mechanisms: the positive accelerate the global warming trend, and negative slow it down.

Positive feedbacks:

  1. Melting of tundra
  2. Reduction of albedo where ice caps have melted at high altitudes
  3. Depletion of ozone in upper atmosphere letting through more short wave radiation to ground level
  4. Net deforestation (more CO2 released than taken up by growth)

Negative feedbacks:

  • Increased cloud cover (more reflected sunlight)
  • Increase in precipitation at poles (reducing sea level rise)
  • Increased CO2 uptake in oceans
  • Thermal mixing in oceans slowing expansion of water
  • Air pollution by certain chemicals (e.g. sulphate aerosols and SO2), reducing short wave radiation received at the surface
  • Net reforestation (extra CO2 in atmosphere leads to increased growth in vegetation)

There are other effects, but it is uncertain if they cause a net positive or negative feedback:

  • Non-linear responses by atmosphere to increasing GHG levels
  • Solutions of equations in GCMs (General circulation model, or global climate model, climate modelling)
  • Certain cloud types


You must log in to post messages.