What is the study of past climates known as
Palaeoclimatology
What are climate proxies
Preserved characteristics of the past which act as a natural recorder of climate variability.
What are the 5 methods of climate proxies
Tree rings
Ice cores
Fossils
Pollen records
Sea floor sediments
Explain the use of sea floor sediments as a climate proxie
Oldest records are 100million years old
Fossil shells of foraminiferia which have calcium carbonate chemical composition in shells, can tell us about sea level temperature.
Mud cores are collected from sea floors and analysed.
Explain the use of ice cores as a climate proxie
Oldest records are 2.7million years ago.
Ice contains pockets of air which provide info on the gaseous composition of the earths atmosphere back then.
Relative frequency of hydrogen and oxygen with stable isotopes can be studied.
The lower the frequency of isotopes the colder the climate.
Explain tree rings as a climate proxy
Influenced by the temperature and rainfall ie. The climatic conditions.
Patterns analysed in widths, density and isotopic composition that all give indications.
In uk/ other temperate climates trees produce a new ring every spring- some survive for thousands of years.
Thicker tree rings indicate periods of fertility, narrow rings periods which are drier.
Evidence may not be overly reliable as other factors such as soil and pollution may affect.
What are the two internal forcings which amplify climate change
Continental drift
Volcanoes
How did the joining of the north and South America (Panama) lead to the glaciation of the Arctic
Intensified Gulf Stream
More evaporation
Less salinity in ocean
Less density of water
Less downwelling
Growth of ice sheets in the arctic
How did the southward drift of Antarctica affect the climate
Cools the circumpolar current insulating the Antarctic with cooler oceans
Cooler oceans store more Co2 lowering it from 1200ppm too 600 ppm.
Increased albedo to 0.95 increases reflection of radiation.
Explain how volcanoes affect the climate
Volcanic gases like sulfur dioxide are injected into the stratosphere which causes global cooling as sulphate aerosols can cool the climate and deplete the earths ozone layer. Volcanic CO2 is also released but the reflectivity of solar radiation from sulphur dioxide is much more effective.
Give an example where an eruption of a volcano has cooled the earths climate
Tambora Indonesia erupted April 1815 ejecting 80million tonnes of SO2
Lead to a drought in India and freezing temperatures in Europe for 3 years
What are the two external forcings effecting climate
Milankovitch cycles
Solar output
What are the three cycles collectively known as milankovitch
Orbital eccentricity- stretching of earths orbital patterns happens ever 100,000 years
Obliquity- tilt of the earths axis, more tilt decreases ice and happens over a 40,000 year period
- range of 22 degrees to 24.5 degrees both have significantly different impacts on climate
Solar output- weakening of suns magnetic field allowing more heat to escape happens ever 11 years
Define the term anthropogenic
Originating in human activity (cheifly of environmental pollution and pollution)
What are 4 which humans are adding to atmospheric greenhouse gases and give AO1 evidence
Burning fossil fuels- since 1850 CO2 has increased as global population increases- more energy dependent
Industry- 1000kg produces 900kg CO2 (5% of global CO2)
Agriculture- 1/4 of CO2 emissions globally
Deforestation- commercial logging and slash and burn releases CO2 stored in trees
Explain how the greenhouse effect works and state the main greenhouse gases
Incoming short wave radiation from the sun is reflected back as long wave radiation off the earths surface
The long wave radiation is then absorbed by greenhouse gases
It is then redirected back to earth causing the warming greenhouse effect.
The main greenhouse gases are methane and carbon dioxide.
What are the three factors which explain the increase of CO2
- Huge demand for energy due to industrialisation and technological advances
- Massive global population growth from 1 billion in 1800 to 7.4 billion in 2015
- Land use change especially deforestation and the draining of wetland for food production and urban development
