Causes Of Climate Change Flashcards
How long is the current Quaternary Period?
2.6 million years.
What are the natural (long-term) causes of climate change?
Milankovitch cycles :
Orbit shape (eccentricity) - Every 100,000 years, the Earth’s orbit changes from near-circular to elliptical due to the gravitational pull of other planets in the solar system. The elliptical orbit varies the distance between the Sun and Earth at different points ; inducing glacial and interglacial periods.
(Axial) Tilt - Every 41,000 years, the tilt of the Earth’s axis moves between 21.5 and 24.5 degrees under the influence of the moon’s gravity ; affecting the planet’s seasons.
Wobble (precession) - Every 20,000 years, the ‘wobble’ of the Earth’s axis varies ; affecting seasonal temperatures and the length of days.
What are the natural (medium-term) causes for climate change?
Sunspots vary the Sun’s solar radiation output on an irregular 11 year cycle.
If there is a decrease in sunspots, then there is a decrease in solar radiation output.
So, there is a cooling effect - if enough ice forms, the Albedo effect could trigger a ‘little ice age’.
Conversely, if there is an increase in sunspots, there is an increase in solar radiation output.
So there is a warming effect - if enough ice is melted, this could trigger something similar to the ‘Medieval warm period’.
What are the natural (short-term) causes for climate change?
Volcanic activity can cause a cooling effect and reduce the Earth’s global temperatures to enact a volcanic winter.
Volcanic pyroclastic ash is released, which can block out and scatter the Sun’s rays.
Eruptions release sulphurous gases, which oxidise to become sulphuric acid droplets ( aerosols ) that reflect the Sun’s heat.
Describe the human activities that enhance the greenhouse effect.
Deforestation - Cutting down trees reduces the amount of CO2 that is absorbed and stored in the trees to be used for photosynthesis , meaning that there are higher levels of CO2 in the atmosphere.
Agriculture - Rice farming and livestock produce around 25% of global methane emissions, due to the heavy cultivation of rice across the globe and a high demand for meat and animal products to feed the growing population.
Fertilisers - Produce nitrous oxides, which are extremely efficient at trapping heat in the atmosphere.
Landfill - Promotes the rotting of waste which releases methane ( CH4 ).
Burning fossil fuels - Energy from coal, oil and gas generates electricity, fuels transport and heats homes. Greenhouse gases such as CO2 and water vapour are released, which concentrate in the atmosphere to enhance the greenhouse effect.
