Unit 2 - The causes of global climate change Flashcards
What are the four layers of the Earth’s atmosphere (from bottom to top)?
troposphere
stratosphere
mesosphere
thermosphere
What is the composition of the Earth’s atmosphere?
78% nitrogen
21% oxygen
0.9% argon
carbon dioxide, helium and ozone
Insolation
incoming solar radiation (short-wave) is the main energy input
What does the intensity of insolation depend on?
latitude, season, cloud cover, time of day
Long-wave radiation
radiation of energy from the Earth into the atmosphere, for some of it, into space
The greenhouse effect
a process by which certain gases (greenhouse gases) allow short-wave radiation from the Sun to pass through the atmosphere but trap an increasing proportion of outgoing long-wave radiaton from the Earth. This radiation leads to a warming of the atmosphere.
It’s a good thing, as there wouldn’t have been life without the greenhouse effect - the Earth would have been too cold for life.
What are some greenhouse gases?
Water vapour - accounts for 95 per cent of greenhouse gases by volume, but it is not implicated in global warming.
Carbon dioxide (CO2) - generated from the burning of fossil fuels, deforestation.
Methane - cattle, natural wetland and paddy fields, bogs trapped in permafrost
Chlorofluorocarbons (CFCs) - synthetic chemicals that come from refridgerators, solvents
Why does the Earth’s temperature change?
Changes in solar output from the Sun
Evidence of the 11-year solar cycle
Changes in the Earth’s orbit of the Sun
The Milankovitch Cycles
Eccentricity - Earth encounters more variation in the energy that it receives from the Sun when Earth’s orbit is elongated than it does when Earth’s orbit is more circular
Tilt - the tilt of the Earth’s axis varies between 22.2° and 24.5°. The greater the tilt angle is, the more solar energy the poles receive.
Precession - a gradual change, or “wobble’, in the orientation of the Earth’s axis affects the relationship between Earth’s tilt and eccentricity.
Global dimming
gradual reduction in the amount of sunlight reach the Earth’s surface. Temporarily cools the Earth for months or years.
Explain the process of global dimming
Natural particles in clear air provide condensation nuclei for water and therefore provides many more sites for water to bind to.
The droplets formed tend to be smaller than natural droplets, which means that polluted clouds contain many more smaller water droplets than naturally occuring clouds.
Many small water droplets reflect more sunlight than fewer larger droplets, so polluted clouds reflect far more light back into space, thus preventing the Sun’s heat from getting through to the Earth’s surface.
Examples of positive feedback loops
(Increase in temperature) -> Melting of methane hydrate -> release of methane gas into the atmosphere -> additional warming -> more melting
increase in temperature -> arctic sea melts -> albedo reduced -> increased absorption of solar radiation -> temp increases
Examples of negative feedback loops
An increase in carbon dioxide in the atmosphere leads to increased plant growth by allowing higher levels of photosynthesis; increased plant biomass and productivity would reduce atmospheric concentrations of carbon dioxide.
Burning, leading to more aerosols and thus reduced solar radiation at the surface, thereby causing cooling.
The human enhanced greenhouse effect
caused by humans. It happens when extra gases produced by us have made the amounts of greenhouse gases in our atmosphere more concentrated. This layer therefore stops more of the long wave radiation escaping space and remits more of it towards the Earth. The planet is heated up because of this.
The increase in the world’s greenhouse gases is linked to industrialisation, trade and globalisation.
