Factors influencing climate on the Earth

Ellipticity of Earth's orbit (1.7 percent)

What time of year the Earth is closest to the Sun and furthest to the Sun. Presently, we are closest to the Sun in January. This depends on precession of the equinoxes (time scale 26,000 years).

Tilt of Earth's axis of rotation to the plane of its orbit (obliquity of the ecliptic). Varies from 22 to 24 degrees on a time scale of 41,000 years.

Carbon dioxide cycle (time scale ~100,000 years)

Lake Nyos, Cameroon, Aug 26, 1986 – carbon dioxide degassing from lake situated in the throat of a dormant volcano. Volcano effluvia can affect sunlight reaching surface of the Earth.

Methane exhalations from the bottom of the ocean can occur. Cows in particular produce methane.

Coal burning power plants and deforestation of the Amazon affect the carbon dioxide content of the atmosphere. Driving cars produces carbon dioxide.

Effect of the Sun on Earth's climate

Sun has brightened ~30% over the last 4 billion years

11 year sunspot cycle causes the Earth's atmosphere to be thicker (extend to higher altitude) when there are lots of sunspots.

When there are few sunspots for a several decades we can experience a mini-ice age (1650 to 1750 AD).

Of course, let us not forget the biggest suddeninfluence on the Earth's climate: the collision ofmulti-km sized asteroid or comet nucleus. Thatcould easily lead to mass extinctions.

The time scale for collisions of the Earth with suchobjects is 10 to 100 million years.

What is the chemical composition of the Earth?

seds.lpl.arizona.edu/nineplanets/earth.html

The crust of the Earth is mostly SiO2. The core

is liquid iron and nickel. The Earth is the densestmajor body in the solar system.

By mass, the Earth is 34.6 % iron, 29.5 % oxygen,15.2 % Si, 12.7 % Mg, 2.4 % Ni, 1.9 % sulfur,0.05% Ti, and 3.65 % everything else. Given theatomic masses of Fe, O, and Si, if we count therelative numbers of atoms in the Earth, oxygenis the most common atom, followed by Fe,then closely followed by Si.