1. Natural climate change
WORLD AT RISK

2. Natural reasons for changes in climate
If the earth’s climate has fluctuated throughout history then surely there must be some natural reasons for this
NATURAL REASONS FOR CLIMATE CHANGE

3. 1. Variations in the Earth’s Orbit
Milankovitch Cycles
A Serbian physicist working at the beginning of the 20th century.
He identified 3 variations in the Earth’s orbit around the Sun
Milutin Milankovitch

4. Eccentricity
Every 100,000 yrs the Earths orbit changes from spherical to elliptical, changing solar input

5. Obliquity of Tilt
The Earth’s axis is tilted at 23.5o, this changes over a 41,000 yr cycle between 22o & 24.5o, affecting solar input, especially in higher latitudes.

6. Precession
The Earth’s axis wobbles, so which way the hemispheres are facing to the sun when closest to the sun varies over 21,0000 yrs. Affecting solar input.

8. Combining all 3 together is “Solar Forcing”

9. 2. Variations in Solar Output
The sun’s output is not constant is also varies. A variety of cycles have been detected, most are short term, the most obvious is Sun Spot activity – 11yrs

10. Mt. Pinatubo erupted in 1991 and resulted in a drop of 0.8°C
3. Volcanoes
Volcanoes were originally responsible for creating our atmosphere
Gases and particles are emitted into the atmosphere during an eruption these can change our climate.
Mt. Pinatubo erupted in 1991 and resulted in a drop of 0.8°C

11. 3. volcanoes
Very complex, some gases warm, some cool, particles tend to cool, each eruption will be different

12. So could It be natural?

13. Could it all just be natural?