Climate basics

This is covering up the map key

This is covering up the map key

Greatest challenge?

The issue of climate change is one that we ignore at our own peril…..

….. unless we free ourselves from a dependence on these fossil fuels and chart a new course on energy in this country, we are condemning future generations to global catastrophe

George W Bush

Atmosphere

• Gas, solids and liquids held in place by gravity

• 50% is found below 6km

Troposphere – 0 to 12km(av)

• Temperatures decrease with altitude - why?

• Wind speeds increase – why?

• Temperature levels out at Tropopause

Stratosphere – 12 to 50km

• Temperatures increase – why?

• Ozone layer at 25 to 30km

• No water vapour or dust

• Temperature levels out at the Stratopause

Mesosphere – 50 to 80km

Temperatures drop until the mesopause (coldest place on Earth, down to -100C

Thermosphere – 80 to 310/620km

Temperatures increase with altitude due to absorption of solar radiation

Climatic Zones

Latitude and Radiation

The variation with latitude of the solar radiation absorbed by the Earth–atmosphere system (solid curve) and the outgoing longwave radiation lost to space (dashed curve).

• Therefore, more solar radiation is always absorbed at low latitudes than high

• At high latitudes more is lost

• The net result is a surplus of heat at the equator

• Basic principles of thermodynamics: heated substances always move towards cooler areas and away from their source of heat – hence the earths circulatory system

Temperature with altitude

Factors affecting the heat budget

• The solar constant• The distance from the sun

– this varies and can cause a 6% change

• The altitude of the sun in the sky – the equator is hotter

• The length of day and night – some regions have 24 hour darkness for two months

The effects of a sphere

• Earth being a sphere alters the angler of incidence the suns rays make with the surface as latitude varies.

• Page 5 in module

Sphericity and the sun

• There are three elements to this:

• The thickness of the atmosphere – higher latitudes make a lower angle to the sun and the atmosphere is thicker

• The suns rays are constant, therefore the more spherical the surface, the more diffuse the effects of the suns rays

• The poles are further away from the sun than the equator

Insolation over a year

Seasonal variation of daily incoming solar radiation (in 10 7 J m −2 ) at the Earth’s surface, taking account of absorption by the atmosphere but ignoring the effect of topography. Note that this is not an ordinary spatial map, but a map, or plot, of incoming solar energy against latitude on the one axis and time of year on the other.

The earths climate system….

Seasons

The four seasons (here given for the Northern Hemisphere) related to the Earth’s orbit around the Sun. When the Sun is overhead at one or other of the tropics, it is the summer solstice (the longest day) in the hemisphere experiencing summer, and the winter solstice (the shortest day) in the other. The red arrows mark the positions in the orbit where the Earth and the Sun are closest and furthest apart. These do not coincide with the black dashed lines, which mark the positions of solstices and equinoxes

Cloud types