Lesson 4:

Natural Causes of Climate Change

What you should know by the end of this lesson:

Know the natural causes of Climate Change

Now that we understand:

What Climate Change is
What is the evidence that supports the existence of Climate Change
What the Greenhouse Effect is

We are going to look at the different range of causes of Climate Change.

Not all are human-created causes. Some are Natural Causes that have affected the climate on our planet for 100 000s of years. Some are very slow processes and some are very quick regular processes.

Climate Change Causes Worksheet

Climate Change Causes Factsheet

Digital Workbook and Paper Jotter

Collect the Climate Change Causes worksheet
Using the information below or the fact sheet to fill in the boxes with information about how Natural factors affect the global climate

Milankovitch Cycle

1491 Causes of climate change.flv

Earth's Wobble

The Earth wobbles on its axis over a 40 000-year cycle. It moves between 22.2 degrees and 24.5 degrees from the vertical, it is current sitting at 23.5 degrees. This is known as the Earth's obliquity. This obliquity is responsible for how much sun areas of the Earth get during different seasons. If the Earth was vertical, there would be no change in the amount of solar insolation or the type of weather we get throughout the year. The further from 0o the Earth is tilted the more solar energy is received at the poles, making that area warmer and the closer to 0o the less solar energy receive making the areas colder.

Earth's Orbit

Earth also rotates around the Sun in an eccentric orbit. This means it is not always a circular orbit. The Earth spins further away from the sun or closer in 100 000 year cycles, moving between an ellipse and a circle. When the Earth is closer it receives more energy from the sun warming the planet. When it is further away, less energy is received making it cooler. We are currently close to a circular orbit, making seasons more even and currently not causing climate change. This is called the Milankovitch Theory

The Milankovitch cycles can be affectionately known as, stretch, tilt and wobble.

Geomagnetic Storms (Solar Flares)

These are changes in the Sun’s activity through sunspots, solar flares/wind and solar radiation. These happen regularly, around every 11 years. An increase in radiation means more heat getting to the planet causing periods of warming.

Read more on this topic here: Scientific American

Volcanic Eruptions

1503 Powerful volcanic eruptions - Mount Pinatubo.flv

Volcanic Eruptions release huge amounts of greenhouse gasses such as sulphur dioxide into the atmosphere as well as tons of ash. Sulphur dioxide is readily oxidized into sulfuric acid over a couple of weeks. This then creates greater interference with the energy coming from the sun blocking it from getting to the surface of the planet. This then has a cooling affect in the local climate near volcanic eruptions. Large eruptions such as Mount Tamboro, Indonesia in 1815 caused a global cooling effect of 0.53oC. In Europe in 1816 it was called the Year Without Summer, leading to harvest failures.

Melting Permafrost

What permafrost is, is in the name. It is an area of permanently frozen ground

Perma= Permanently Frost = Frozen

Melting permafrost has two significant effects on Climate Change. Large deposits of methane gas are stored within the Antarctic and land-based ice. This is a prominent greenhouse gas that is released as the permafrost melts leads to more global heating.

Permafrost also tends to be white in colour, this reflects sunlight and heat known as the albedo effect. Water has a lower Albedo score than ice, so absorbs and stores more of the heat within the planet.

Ocean Currents

Oceanic Circulation is a huge driver of air masses around the planet, moving warm air from the equator to the poles and transferring cold air to the equator. Disruption to these oceanic circulations can create warming or cooling events. Melting freshwater ice in the North Atlantic will disrupt the North Atlantic drift, moving it further south lowering the temperature for western Europe and the U.K.