Science 10 - Climate: Energy Flow in Global Systems

Part 1 – Energy Transfer on Earth

Defining Systems

A system: object or group of objects that is being studied

Open system: allows energy and matter to cross the system’s boundary

Closed system: allows only energy but not matter to cross the boundary

Isolated system: allows neither matter nor energy to flow across the boundary.

Which type of system is Earth? An open system, though rare for matter to cross boundary

The global system that we will mostly study is the Biosphere

Biosphere: thin layer of air, land and water on or near the Earth’s surface (all life on earth exists in this thin layer)

The atmosphere: the air - mixture of nitrogen, oxygen, and other gases extending 800 km above Earth’s surface. Troposphere is layer closest to earth, then the ozone layer and stratosphere.

Lithosphere: the land

Hydrosphere: the water on or near Earth’s surface – oceans, rivers, lakes, clouds, glaciers, etc.

Earth’s Perfect Temperature for Life

Earth has been able to sustain life arguably largely due to its temperature. So where does Earth get its heat from and how does it maintain it?

Earth’s Radiation Budget

Earth gets its energy from the sun through solar radiation.

Radiation: mechanism of energy transfer in which atoms or molecules emit electromagnetic waves

When solar radiation interacts with matter it can be absorbed or reflected.

If absorbed it will warm up (transfer to the matter in the form of heat) the matter

Visible light reaches surface unchanged where it is reflected or absorbed.Absorbed light warms the surface.

49% of the radiation reaching Earth is absorbed by the surface, while 9% is reflected by the surface. The other 42% is absorbed, reflected and scattered by the atmosphere.

Dust particles and gases in the air scatter sunlight – this is where the colour of the sky comes from.

Clouds and the gases in the atmosphere will also absorb infrared radiation.

The reflectivity of a surface is referred to as its albedo (a percentage of the amount of light reflected). Ex. Snow covered field might reflect 70-80% of light, while the same field with no snow might reflect only 20%.

If the Earth only absorbed energy from the sun the planet would continue to warm up and warm up until it was unbearably hot…so how does it maintain its temperature?

All matter emits energy in the form of infrared radiation. In doing so, that matter cools down.

Earth’s surface emits IR radiation, which is absorbed by the atmosphere and then re-emitted by the atmosphere into outer space.

Why doesn’t heat just radiate into space at night, cooling off Earth once the Sun sets?

Greenhouse gases absorb IR radiation from the surface and transmit it in all directions. This is called the greenhouse effect.

Greenhouse gases include: CO2, H2O, CH4, N2O, O3 and chlorofluorocarbons and hydrofluorocarbons (eg. CF2Cl2)

Climate Change

Weather: conditions of temperature, atmospheric pressure, precipitation, cloud cover, humidity, etc. in a region at a certain time.

Climate: trend/average in weather over a period of many years (30+ years)

Climate change: significant change in climate over a long period of time

Scientiific evidence of climate change:- Climate (daily high temperatures)- Sea levels- Fossils- Vegetation- Tree rings- Ice cores (istopes)

Anecdotal evidence is based on non-scientific observations