Our Planet’s Changing Climate

Forcing and Feedbacks

Our Climate Has Changed Throughout History…

GREEN HOUSE EFFECT

Climate Forcing Several Factors Naturally Change

Climate (Climate Forcers)• Tectonic Processes• Strength of the Sun• Orbit Changes

Humans also Impact Climate• Anthropogenic Impacts

Milankovitch Cycles Three properties impact insolation

from the sun: (This is an external forcing)

• 1) ECCENTRICITY (SHAPE)

• 2) OBLIQUITY (TILT)

• 3)PRECESSION (WOBBLE)

ECCENTRICY: ORBIT SHAPE Describes changes

in distance from the sun as the shape of the elipse changes.

Cycles every 100,000 years

OBLIQUITY: TILT OF THE AXIS The earth’s tilt is the

most dramatic influence on seasons because it results in dramatic differences in the amount of solar radiation in each hemisphere throughout the year.

Cycles every 41,000 years

PRECESSION: EARTH’S WOBBLE Due to the

gravitational pull of the sun and moon

Think of a spinning top

Impacts strength of seasons when shape is elliptical

Cycles every 23,000 years

FEEDBACK LOOPS Positive---Amplifies

the Impact

Negative—Regulatory---Controls the Impact

FEEDBACKS: INTERNAL FORCING Feedbacks can be

• positive or negative• Natural or

Anthropogenic

Example of Positive Feedback (Melting of the Permafrost)• Melting Permafrost