Lecture 1: An introduction to ESS

## **Earth System Science: Lecture 1 (An introduction)**

**What is Earth System Science?**

* Interactions of physical processes on different scales
* Application to the human world - Earth systems include people
* Environmental problems - Looking at Earth systems helps with this
* Resource management -  Looking at Earth systems helps with this
* Earth systems are interconnected.
* Lovelock, 1979 said that they Earth is a self regulating planet, with a range of interconnected systems making the world what it is. This is now known by scientists and geographers as Earth System Science.
* If you adjust one system then it has a knock on impact affecting other systems, altering the world.
* Anything that happens on the planet is part of an Earth system.

**What is a system?**

Definition:

* Systems contain energy
* Systems contain matter
* Energy (and sometimes matter- not all the time) is exchanged between a system and its surroundings.
* E.g Exchange of water between the ocean and the atmosphere.

**Different types of system:**

* Open system (free transfer of both mass and energy). Open systems have inputs, throughputs and outputs (and changes in states). A lot of the Earths systems are open. E.g Water from river flow —> Ocean —> Evaporation
* Closed system (transfer of energy, no transfer of mass) E.g if you put a lid over a pan of boiling water and then put your hand over it, you can still feel it is warm, but you wouldn't get the moisture on your hand.
* Isolated system (no exchange of energy or mass). It should trap both the energy and the mass. In reality, we cannot even think of the energy as a whole as an isolated system. However, if we went out to the entire universe we can argue that this is an isolated system as there are no interactions beyond the universe (apparently). This could be the only example of an isolated system.

**Characteristics of systems:**

* They can be found on different scales: From global to atomic
* They have limits: They have boundaries, they have to have an edge. E.g a watershed marking the boundary of a river system.
* Are associated with processes: They means by which changes to the system are made (The ways how matter or energy are transferred within and between systems).
* Energy cannot be created or destroyed (1st law of thermodynamics).
* Energy transfer is not 100% effective, some energy will be lost such as from heat, and wont be able to do the work in the system.
* Entropy- The amount of lost energy that builds up.
* Pathways or patterns can change if inputs, throughputs and outputs change. E.g a stream hierarchy.
* Adjustments to the system also takes place. Inputs, throughputs and outputs are in balance so if one changes they all change.

**Important terms (Could be asked to define these in an exam):**

**Feedback:**

* Negative feedback: The system isn't changing very much, it is always returning to its regular state. The processes and mechanisms maintain a steady state. The system is in control. This is called homeostasis.

* Positive feedback: The processes or mechanisms lead to a change with a cumulative effect in a system and cannot go back to its original state. The system is out of control. This is called homeorhesis.

**Threshold:**

When a component of the system reaches a critical value above which there is a dramatic chant in the way the system works… (See image on the right)

**Ideas of tipping point:**

* Lenton et al came up with a map of potential relevant tipping elements in the climate systems.
* However, the concept of a global tipping point has major policy implications. It suggests that below some threshold nothing serious will happen, but after that all will be lost. This view risks complacency on one side and hopelessness on the other (Ellis, 2013).

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Earth System Science <- Click here to go back to the overview of Earth System Science

Year 1 <- Click here to go back to the overview of all first year modules.