Fundamentals of Physical Geography

2nd Edition
James Petersen
ISBN: 9781133606536



Fundamentals of Physical Geography

2nd Edition
James Petersen
ISBN: 9781133606536
Textbook Problem

What are the major causes of global climate change?

To determine

The major causes of global climate change.


Numerous theories about the natural causes of change in climate can be categorized into five broad classes. They are the astronomical variations in the orbits of the Earth, changes in oceanic circulation, changes in the distribution of landmasses, asteroid and comet impacts, and atmospheric changes.

The distance between the Sun and Earth and the deviation of axis of the Earth from the plane of the ecliptic affects the cyclic changes in the orbit of the Earth. This is known as Milankovitch theory or astronomical theory of climate variation. These orbital cycles result in a regular variation in the solar energy amount that reaches the Earth. Three different cycles are involved under the Milankovitch cycle. They are the eccentricity cycle, obliquity cycle, and a precession cycle. Eccentricity cycle is the longest cycle that has a 100,000 year modification of the shape of Earth’s orbit around the Sun. It causes a shift from an elliptical to a more circular orbit and back. The relationship between the Sun and the Earth are affected by these orbital variations. Obliquity cycle is the second cyclic change that denotes a 41,000 year variation in the tilt of Earth’s axis from a maximum of about 24.5 to a minimum of 22.0 and back. The more tilting of the Earth results in a greater seasonal differences in the middle and high latitudes. The less tilts cause cool summers with less ice and snow melting to polar regions and it may cause a period of glaciation. The third cycle that has a periodicity of 21,000 years is termed as precession cycle. It determines the time of year that Perihelion occurs. All these three cycles are operated together and its combined effects indicate that during an interval of 1 million year, numerous glacial cycles occurred. The studies proved that the correlation exists between Milankovitch’s predictions and paleoclimate evidence from deep-sea sediment cores and the glacial ice cores indicates that the regular orbital cycles are the major driving force behind glacial-interglacial cycles and the long term cycles of climate are predictable.

More than 70% of the Earth’s surface is covered by oceans. The massive volume and higher heat capacity of global ocean make it largest buffer against the Earth’s climate change. The global climate is significantly influenced by the variations in oceanic temperature, chemistry, or circulation.

Surface oceanic currents are driven mostly by winds

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