7.1 A - How and Why Climate has Changed in the Last 10 000 Years
A- How (and why) Climate has Changed in the Last 10 000 Years (since the last ice age)
- Large changes over a short amount of time.
- End of last ice age – 8000BC
- Always fluctuating
- Little ice age 1200-1800
- Rapid temperature change --> 1200 years 5 degrees temp change
- 10000 years fluctuation = short
CAUSES (WHY?) :
Volcanic activity –
Release large amounts of sulphur dioxide (SO2) haha. This is chem. X) and ash
A layer of these particles act as a ‘cloak’ (like... a protective layer) around the earth
Thus, reducing the amount of solar energy (radiation) (OMG PHYSICS!!) that reaches the Earth’s surface
Orbital Geometry
Orbital characteristics / Orbital Geometry => Milankovitch cycles
1. Shape of earth’s orbit varies from CIRCULAR to ELLIPTICAL to CIRCULAR
every 95 000 years
COLD, glacial periods – circular
WARMer periods – elliptical
2. Tilt of earth’s axis varies -> affects intensity of seasons
from 21.5° to 24.5°
Variation over 40 000 year span
The GREATER the angle, the hotter the summers are and colder the winters are. LARGE VARIATION
The SMALLER the angle, the SMALLER the variation between seasons.
**NOTE: Different sources say earth’s axis varies from 22.5 – 24.5 degrees over 41000 year period**
3. Precession of the earth -> affects timing of seasons (relative to orbital position to the sun)
The earth’s axis precesses (wobbles like a dying spinning top) over the course of 25 000 years
View animations of the milankovitch cycles: http://www.wwnorton.com/college/geo/egeo/flash/18_2.swf
Solar output –
Energy from the sun changes over time
More energy ->high temperature
Less energy -> cooler temperature