Feedbacks in the climate systemFeedbacks in the climate system

Feedbacks in the climate system

According to the Australian Academy of Science:

The science of climate is at the intersection of a number of science disciplines and sub-disciplines. At its heart are physics, chemistry, biology and mathematics - each with their sub-disciplines of atmospheric physics and chemistry, oceanography, hydrology, geology etc - and each of which can be considered as mature within the framework required to discuss climate.

It is at this intersection of the disciplines where uncertainty can and will arise, both because of the yet poorly understood feedbacks and processes within different components of the climate system, limitations of observing system used to develop and validate climate models, and because of the difficulty of bringing these components together into a single descriptive and predictive model.

This would include, for example, the biological consequences of how increasing carbon dioxide (CO2) feeds back into climate and into the climate model, or how the consequences of atmospheric warming on water vapour, cloud cover, ocean warming and circulation interactions can be described and quantified in a coherent and integrated theory.

It is these feedbacks and interactions that make it difficult to realistically quantify the uncertainty in the outputs of climate models at levels that the experimental scientist is usually accustomed to. In a process as intrinsically complex as climate it should not be surprising that the path to understanding is long and arduous.

According to the Garnaut Review released in 2011 "there is a high level of uncertainty about how the carbon cycle will respond to climate change".

The net effect of all climate feedbacks is to amplify the warming caused by increasing emission of greenhouse gases.

Feedbacks that scientists are researching intensively include ocean heat uptake, changes in terrestrial and marine biosphere, clouds and water vapour, ice sheets and sea-ice,. For example

  • Decreasing ability of the oceans to remove carbon dioxide from the atmosphere with increasing water temperature, reduced circulation and increased acidity (IPCC 2007a: 531);
  • Weakening of the uptake of carbon in terrestrial sinks due to vegetation dieback and reduced growth from reduced water availability, increased soil respiration at higher temperatures and increased fire occurrence (IPCC 2007a: 527; Canadell et al. 2007); and
  • Release of carbon from long-term sinks such as methane stored deep in ocean sediments and in frozen soils as temperatures increase (IPCC 2007a: 642).
  • Snow and ice melt reveal darker land and water surfaces which absorb more of the sun's heat, increasing the rate of melting and creating a self-reinforcing cycle.
  • Changes in cloud cover are closely coupled with other feedbacks including the water vapour feedback and the ice-albedo feedback.