The climate system

Last week I started a MOOC course on climate change at Exeter University, as the final exercise of the first unit, we were asked about some reflections on the topics we have learned.

We can understand the climate as a system where different components: Atmosphere, Hydrosphere, Biosphere, Cryosphere and Lithosphere, interact. There are a wide range of natural cycles, but the water cycle is the one which illustrates better the climate system. Solar radiation causes the evaporation of the water from lakes, rivers and oceans (hydrosphere). and also water evaporation and transpiration from green plants (biosphere). The water vapor condenses in the atmosphere forming clouds and then it returns to the surface through precipitation as rain and snowfall. When reaches the surface, water returns either to the hydrosphere or to the cryosphere, if it is frozen snow. Sunlight can melt snow and ice or transform it into vapor from the ice sheets, snow fields and glaciers, by sublimation. All those processes are influenced by many factors including human activities.

When we consider the dynamics of our climate system, we’re not just talking about simple cause and effect. The cycles that connect components of the climate system create feedback loops, as well; closed loops of cause and effect. Here the three key feedbacks that play an important role in our climate system: Water vapor feedback, ice albedo feedback, and the radiation feedback.

1.       Water vapor feedback: As the evaporation increases, more water vapor on the atmosphere and a increase of temperature, that helps the evaporation, and so on. This is a positive feedback.  

2.       Albedo feedback: The sea ice has a high albedo but the ocean has a low albedo. The radiation arrives at the ocean and it is absorbed. The sea ice melts, and produces an increase on the ocean water. Then the albedo of the sea ice decreases and so the reflection, increasing the absorption of the sea. This warming on the ocean will melt more sea ice, and so on. This is another positive feedback.   

3.       Radiation feedback: Stefan Boltzmann effect or Planck feedback. All the objects give off radiation, and when this happens, the object cools it down. This is an example of negative feedback.

Thanks to the different positive and negative feedbacks this systeself-regulates itself. 

Useful links:
·        NOAA - Climate http://www.climate.gov/
·    Professor Tim Lenton's Climate Change MOOC blog - http://blogs.exeter.ac.uk/climatechangemooc/