Transcript Climate Change - Shawlands Academy

Climate Change
Reasons for climate change divide into 2 main causes;
natural and human
Natural Reason
Human Reasons
Variation in insolation
Astronomical Changes
Volcanic Eruptions
Plate Tectonics
Changes in Ocean Currents
Enhanced Greenhouse
Effect
Variations in Insolation
Evidence suggests that the amount of heat energy
from the Sun is not always the same, but that there
are cycles of increased solar energy – sunspots
Astronomical Changes
1. The 95,000 year stretch
The earth’s orbit changes from circular to elliptical
and back again, when it is elliptical some areas
will be nearer the sun than they were and some
further away, so some will be hotter, others colder.
2. The 42,000 year tilt
The tilt of the earth’s axis changes from 21.5 to 24.5
degrees and back again – the greater the angle of tilt,
the greater the area receiving the Sun overhead
3. The 21,000 year wobble
The axis also wobbles, meaning that some areas get
more insolation at some times than others.
When all these 3 are giving thier lowest insolation at
the same time, that is when the Earth is most likely to
have major glacial periods.
Volcanic Eruptions
Large volcanic eruptions
cause extra dust particles
in the atmosphere which
absorb more solar
radiation, lowering
temperatures.
When many eruptions
occur over a short time,
this can significantly lower
temperatures.
Krakatoa (1883) Mt St Helens (1980) Mt Pinatubo (1991)
Plate Tectonics
Continents have had different climates in the past because they
have been in different latitudes due to continental drift.
Changes in Ocean Currents
Changes in the pattern and strenght of ocena currents may
lead to changes in the distribution of heat around the planet.
A short term example might be El Nino which happens every
couple of years.
Task
Think of the different types of human activity
that takes place.
What activities might cause changes in
climate?