Download Volcanoes - BSHGCSEgeography

Natural/ physical causes for
climate change
LO: to
explain the
natural
cause of
long term
climate
fluctuations
Industrialisation
Homo Sapiens
Orbital geometry
Milankovitch cycles
https://www.youtube.com/watch?v=TWJyeyV92W4
• Earth's climate undergoes 120,000 year cycles of ice
ages broken by short warm periods called
interglacials.
• The cycle is driven by Milankovitch cycles. Long term
changes in the Earth's orbit trigger an initial warming
which warms the oceans and melts ice sheets - this
releases CO2.
• The extra CO2 in the atmosphere causes further
warming leading to interglacials ending the ice ages.
• For the past 12,000 years, we've been in an
interglacial.
• The current trend of the Milankovitch cycle is a
gradual cooling down towards an ice age.
Changes in solar output
•
Caption for Image Four: The Sun shows signs of variability, such as its eleven-year sunspot cycle.
In that time, it goes from a minimum (seen here in 1996) to a maximum (2000) period of activity
that affects us everyday. When particularly active, solar storms can spew tons of radiation to Earth
in the form of Coronal Mass Ejections (CMEs) that can affect power grids, spacecraft, and
communication systems.
SUPER: NASA / ESA
Catastrophic events-e.g.
volcanic eruptions
https://www.y
outube.com/
watch?v=Pd
EWUoSOJ7
M
Volcanoes
•
•
•
•
•
•
Volcanic eruptions spew sulphate aerosols into the atmosphere which
has a cooling effect on global temperatures.
These aerosols reflect incoming sunlight, causing a 'global dimming'
effect. Usually, the cooling effect lasts several years until the aerosols
are washed out of the atmosphere.
In the case of large eruptions or a succession of eruptions such as in
the early 1800's, the cooling effect can last several decades. Strong
volcanic activity exacerbated the Little Ice Age in the 1800's.
Observational and modelling studies (e.g. Kelly & Sear, 1984; Sear et al.,
1987) of the likely effect of recent volcanic eruptions suggest that an
individual eruption may cause a global cooling of up to 0.3°C, with the
effects lasting 1 to 2 years.
Such a cooling event has been observed in the global temperature
record in the aftermath of the eruption of Mount Pinatubo in June
1991. The climate forcing associated with individual eruptions is,
however, relatively short-lived compared to the time needed to
influence the heat storage of the oceans (Henderson-Sellers &
Robinson, 1986).
The temperature anomaly due to a single volcanic event is thus unlikely
to persist or lead, through feedback effects, to significant long-term
climatic changes.
How do each of these factors
cause climate change?
Sample question
Mark scheme