Causes of Climate Change Flashcards
difference in sun output on Earth’s temperature
a 1% difference in output would lead to a change of only 0.6°C in Earth’s mean annual temperature.
Nearest and farthest point of orbit
The nearest point of this orbit is known as the perihelion and the furthest point is known as the aphelion.
perihelion during northern hemisphere winter:
If Earth is at the perihelion during the northern hemisphere winter it will receive more energy and therefore be warmer than it were at the aphelion at that time.
Ellipticity cycle
A complete cycle takes about 22,000 years and is termed the precession of the equinoxes
Degree of ellipticity cycle
The degree of ellipticity of Earth’s orbit changes through time over a cycle of about 96,000 years, this phenomenon is known as the eccentricity of the orbit
Earth’s axis of rotation can range between:
it can range from 21.8° to 24.4°
When the earth’s axis of rotation has a greater tilt
When the axis has a greater tilt, the position of the sun at midday and the solstices is further polewards by about 2.5° than when the tilt is is smallest. This produces greater seasonal contrast with high tilt and less contrast with a small tilt.
Changes in Earth’s orography
Changes in Earth’s orography take millions of years to become significant but they can be significant
Deforestation as an example of changes in surface features:
Deforestation is a clear case of a change in surface properties which, by changing surface albedo and heat budget, could affect climate
Snow/Ice Melt
with snow or ice on the ground much energy will be reflected or consumed in melting or ablating. The recent break up of some of the Antarctic ice shelves such as Larsen B will produce a dramatic decrease in albedo. This will become available for heating when the surface changes potentially producing a marked increase in temperature at the surface.
Conversely, a change to snow and ice would trigger a positive feedback to enhance cooling.
Volcanic eruptions
When a volcano erupts it may expel vast quantities of dust and gases such as Co2 and sulphur dioxide into the atmosphere. If dust and sulphate particles can survive in the stratosphere they are able to reduce by reflection the amount of solar radiation reaching the ground. Major eruptions can result in surface cooling of about 0.2°C for a few years after the event.
Proportion of CO2
We would expect an increase in the proportion of the gas to trap more long-wave radiation emission from the surface and increase the mean temperature of the globe. Since 1958 precise measurements of CO2 levels have been taken at the Mauna Loa observatory. They show an increase from 315ppm by volume to about 380ppm today, an increase of about 20% in 50 years.
Increase in methane
Increase in methane is causing concern. It is believed that a large portion of the methane increase may be a result of anaerobic decomposition of organic matter associated with rice paddy cultivation and the digestive processes of ruminants couch as cattle.
