climate

• temperature decreases with distance from the equator due to the curvature of the Earth

• in areas closer to the poles incoming solar radiation has a 'thicker' atmosphere to pass through  and the sun is at a lower angle in the sky so the incoming solar radiation is spread over a large area. this means that temperatures are low.
• in areas near the equator incoming solar radiation is more concentrated due to the curvature of the earth meaning there is a small distribution area for the solar radiation to cover, making temperatures higher

Hadley Cell: the warm air at the equator rises into the upper atmosphere, then moves away and as it cools, it descends at the tropics

Ferrel Cell: cold air from the poles meets warm air from the tropics in the mid latitudes

Polar Cell: cold air at the poles descends, then moves away towards the mid latitudes

• the sun's radiation heats the earth's surface which heats the air directly above it
• this increaces the amount of energy in the air so it begins to rise
• the rising air exerts less pressure and cannot hold as much water vapour so an area of low pressure is formed on the ground below which results in high precipitation levels

• as the air rises further away from the heated earth's surface it begins to cool and it has less energy so the air begins to sink back towards earth

• the 'weight' of the sinking air exerts more pressure on the ground and an area of high pressure is formed which results in dry, stable conditions

• the oceans redistribute heat around the earth, like air
• ocean currents are driven both by the movement of wind across the surface of the ocean as well as by water sinking and rising due to temperature change
• Eg. cold water in the Arctic sinks, drawing in warmer water from the south. the mid atlantic drift is a warm ocean current from the gulf of mexico that affects the uk.

• over the last 800,000 years climate has been constantly fluctuating with interglacials only occuring roughly every 100,000 years with glacial periods between them
• temperatures alternate between warm periods and cold periods every 400-500 years

Historical Sources: personal diaries, paintings and religious records e.g. Anglo Saxon chronicles written by monks from around 890 to 1150s which recorded years of drought and heavy rainfall

Tree rings: reveal the history of a tree's growth. in warmer years they grow more and there is evidence to suggest climate was cooler in the past when tree rings were closer

Ice Cores: scientists extract cores of ice from the poles and within the ice layers show the history of climate change. when the iceis cut open the gas in the ice can be meassured to compare the greenhouse gases with the temperature at the time

Advantages: gives insight firsthand into what the conditions were like in the past

Disadvantages: could be exaggerated only tells you about climate in certain places

Volcanic activity: Large and explosive volcanic eruptions produce ash and sulphur dioxide gas which is spread around the earth's stratosphere by high level winds. The blanket of ash and gas reflect sunlight back into space and prevent the sun's heat from reaching earth which lowers the average temperatures for a few years.

E.g. In 1991 Mt Pinatubo in the Phillipines erupted and releasee 17 million tonnes of sulphur dioxide which was enough to educe global sunlight by 10% and cool the planet by 0.5C for a year.

Variations in solar output: Sun spots are black areas on the surface of the sun which vary in number. Lots of spots mean more solar energy and radiation is being fired out from the sun towards earth and average temperatures are hotter. 

E.g. The Little Ice Age and the Medieval Warm could have been caused by sunspots.

Orbital Changes: The earth's orbit is sometimes circular and sometimes oval and the earth's axis tilts and wobbles which alter the amount of sunlight the earth receives and where the sunlight falls on the earth's surface. Over thousands of years the changes would be enough to start or end an Ice Age. These are called Milankovitch cycles.

E.g. Colder glacial periods and ice ages were 5-6C colder than today and could have been caused by this.

Asteroid Collisions: Occasionally a comet or asteroid hits earth. An impact of a body this size would release huge quantities of vapourised material into the atmosphere which block out the sun and causes an initial Impact Winter where temperatures drop 5-6C. This is sometimes followd by a temperature incrase due to CO2 released by forest fires.

E.g. Extinction of the dinosaurs 65 million years ago.

• due to the enhanced green house effect global air temperatures are increasing. Between 1901 and 2012 surface temperatures have increased by as much as 2.5C in parts of South America
• upper ocean temperature changes correlate directly with surface air temperature change
• arctic sea ice has decreased overall from 8 million km2 to 5.8 million km2 which results in rising sea levels
• sea levels have risen by up to 20cm threatening the existance of many low lying islands
• almost all areas of glaciers worldwide are thinning some as much as 1m/year
• due to warming seas the destructive power of typhoons have intensified by 50% in the past 40 years
• man made climate change is responsible for the increased regularity of extreme heat waves which are now happening 4 or 5 times as often
• over the last 30 years the number of worldwide floods have increased due to rising sea levels

Causes of CO2:  cars, deforestation, power stations, burning fossil fuels (89% of emissions)

Causes of methane: rice fields, cows, peat bogs, landfill sites, decaying organic matter (7%)

Greenhouse effect: the natural trapping of the sun's energy in the atmosphere due to the presence of greenhouse gases

Enhanced Greenhouse Effect: the increased greenhouse effect resulting from humans emitting more greenhouse gases (from things such as increased car ownership and increased demand for natural resources eg wood and coal) which leads to global warming

in the uk: fewer deaths of elderly people during winter months, heating and road gritting costs could fall, domestic tourism could grow, rising sea levels would need more investment in coastal defences to prevent flooding, more extreme storms threaten more homes, ski resorts have to close due to lack of snow, increase in heat stroke, drought and water shortages

in egypt: extreme water shortages and droughts,undernourishment of the poorest, lower crop yeilds, 7 million people displaced from their homes due to flooding, businesse fail

in the Maldives: 80% of the land area lies below 1 metre above sea level so rising sea levels pose a threat to homes and businesses, 77% of its land area could be lost with 50cm of sea level rise

in Nepal: a reduction in rain will lead to water shortages and irrigation problems for agriculture, crop yeild decrease by up to 30%, increase precipitation will result in river flooding and landslides in mountainous areas which will force people to migrate, 20% loss of snow and ice above 5000 metres for a 1C increase in intemperature

highest projection: + 5.5C                     lowest projection: + 0.25C

Range: 5.5-0.25=5.25C

Uncertainty: (Why?)

• future population is difficult to predict due to factors such as disease, the higher the population change the more greenhouse gases released and the bigger the temperature change
• future economic growth could change as more countries are industrialising and releasing CO2
• future energy supply is hard to predict as there may be efforts to use more renewable energy
• the number of sunspots may vary and are hard to predict so if there are more sunspots there is more solar output so temperatures would increase
• volcanic activity is also difficult to predict and some produce more ash so if there is lots of ash produced by volcanoes temperatures would decrease due to the ash blocking out the solar radiation

highest projection: +0.97m                   lowest projection: +0.28

range:0.97-0.28=0.69

Uncertainty: (Why?)

• if temperatures rise ice caps will melt at varying rates and produce more water
• when water expands with heat the volume is increased so the sea level will rise             (thermal expansion)
• factors from temperature change uncertainty could also effect sea level rise