(5.1.1-5.1.2)- Evidence of and Causes for Climate Change

evidence, natural causes, carbon cycle, human effects on the carbon cycle, greenhouse effect

What is the Quaternary period?

the last 2.6 millions years

What has climate done during the Quaternary period?

Fluctuating- both warmer and cooler than at present

What is a glacial period?

A colder period where glaciers advanced

What is an interglacial period?

Warmer period between glacials

What is the nature of interglacials and glacials?

they’re cyclical- regularly recurring

How have changes in temperature suggested climate change?

Since about 1950, temperatures have steeply increased.

Before, climate fluctuating but remained steady.

What are some other ways climate change can be proved?

instrument readings

glacier readings

ice cores

CO₂ levels

historical data

tree rings

lake sediments

sea floor sediment

fossils

Explain how instrument readings prove climate change.

Comment on the validity.

thousands of meteorological stations around the globe have been recording temperatures for thousands of years.

• site characteristics may change- data cannot be directly compared.

Explain how glacier retreat proves climate change.

Comment on the validity.

• world’s glaciers have been retreating over the last 50-100 years

• suggesting warming temperatures.

  • could be due to reduction in snowfall

Explain how ice cores prove climate change.

Comment on the validity.

• cylinders of ice taken from glaciers/ice sheets have bubbles of air + substances trapped in them.

• these can be analysed for concentrations of gases + things like dust/pollen etc.

• can be indicative of climate.

  • provides range of info

  • deeper the ice- more compressed the layers

  • expensive

  • no snow one year- inaccuracy

  • data represents a period not a year- uncertainty value

Explain how CO2 values prove climate change.

Comment on the validity.

• positive correlation between CO2 conc + global temp.

• global temp. in history can be worked out by CO2 records.

  • reliable data only after 1800

  • vary across local areas

  • easily influenced by external factors

Explain how historical accounts prove climate change.

Comment on the validity.

• reconstruct timeline of Earth’s climate through writings about major weather events

  • author’s reliability

  • lack numerical precision- subjective

Explain how tree rings prove climate change.

Comment on the validity.

• trees record their growth in rings

• good growth with wet + warm conditions = wide rings

• bad growth with cold + dry conditions = thinner rings

  • trees live for more than centuries

  • data often used with weather data and is accurate when it correlates

  • temperate trees only give summer data

  • equatorial trees don’t have rings- they grow all year round

  • influenced by other factors- soil, disease etc.

Explain how lake sediments prove climate change.

Comment on the validity.

• can be recovered and analysed to reconstruct through pollen- plants, charcoal- fires, colour- deposition etc.

  • broad spectrum of data as it can be collected globally

Explain how sea-floor sediments prove climate change.

Comment on the validity.

• fossils + deposits = temperature at the time

• different forams lived in different temperatures

• oxygen isoptope from sediment suggests temperature

  • very expensive

Explain how fossils prove climate change.

Comment on the validity.

• different species need specific conditions

• fossils can help work out climate at the time

  • not necessarily true that species then have the same needs as now

  • fossils may have been moved/weathered

What are the natural causes of climate change?

external:

• solar output/sunspot activity

• orbital geometry

internal:

• volcanic activity

• surface reflection

Explain the effects of solar output on climate change.

• energy from Sun changes over time

• if a trend continues for 100 years

• affects global temp.

Explain the effects of orbital geometry on climate change.

• glacial period = circular orbits

• interglacial period = elliptical orbits

• greater the angle of axis tilt, hotter the summers + colder the winters

Explain the effects of surface reflection on climate change.

• colder periods with greater snow/ice

• more sunlight reflected back into space

• cooler global temperatures

Explain the effects of volcanic activity on climate change.

• volcanic eruption = lots of ash and sulphur dioxide

• act as a cloak, reducing solar energy

• temp decreases

What is the Carbon cycle referring to?

A closed system in which carbon is transferred between the different stores on Earth + the atmosphere.

What is a carbon store?

Somewhere carbon accumulates- more carbon stored that released

What is a carbon source?

Somewhere more carbon is released than stored.

What is a flow in the carbon cycle?

the transfers of carbon between stores.

Describe the carbon cycle, with flows and stores.

A plant releases net CO2 at night by respiring.

It absorbs net CO2 in its life via photosynthesis.

Dead plants transfer locked carbon into soil as they decompose.

Organisms digest tissue and release CO2 into soil/atmosphere as they respire.

Rainwater dissolves some CO2 and carries it into rivers/seas.

Lithosphere is the largest store of carbon.

How do humans affect the carbon cycle?

wildfires- turn biosphere from store to source

burning of fossil fuels- lithosphere store to source

farming practices- tilling releases carbon in soil

deforestation- biosphere store to source

draining of peatland-

• lowered water level means plants within decompose- biosphere store to source

melting of permafrost- cryosphere store to source

Why is the release of stored carbon damaging?

Due to the greenhouse effect, higher CO2 concentrations increase global warming.

Explain the greenhouse effect.

1. Solar radiation heats Earth.

2. Short-wave radiation reflected back to space

3. long-wave radiation trapped and reflected back to Earth by greenhouse gases.

How has increased carbon worsened global warming?

1. increased concentration of greenhouse gases in atmosphere

2. less outgoing radiation reaches space- reflected back instead

3. creates a cycle in which:

   • the Earth continues heating up

   • carbon levels continue increasing