4.3Unit 4: Energy, Environment, Microbiology and Immunity
Climate Change — IAL Edexcel Linear Revision Notes & Topical Questions
10 min read 12 parts Lesson 4 of 28 Unit quiz
Lesson summary
4.3 Climate Change — IAL EDEXCEL LINEAR notes: Explain the greenhouse effect and anthropogenic climate change, evaluate the evidence and models, describe the effects on species and enzymes, and evaluate ways to reduce atmospheric carbon dioxide.Climate = weather conditions in a r…
- Global temperature records
- Pollen in peat bogs
- Dendrochronology
- Correlation and causation
- Enhanced (anthropogenic) greenhouse effect
- Carbon cycle
Part 1 of 9Evidence for climate change
1Climate
Climate weather conditions in a region over several decades,
- and climate change is a significant long-term change in them, now mainly global warming from human activity.
2Atmospheric carbon dioxide
- Atmospheric carbon dioxide ice core bubbles show levels fluctuated through history because of volcanic eruptions and weathering of limestone.
- Deeper ice is older ice.
- Before the industrial revolution the highest level was about 300 ppm,
- and it is now above 400 ppm, with recent increases faster and greater than ever before.
- CO2 and temperature correlate over thousands of years, and sunspots and solar winds have small effects by comparison.
3Global temperature records
- Global temperature records thermometer records since the mid-1800s show an overall rise with short periods of decline, matching the period of fossil fuel burning.
4Pollen in peat bogs
- Pollen in peat bogs peat forms in waterlogged acidic conditions in layers, with older peat deeper.
- Pollen of each species is unique, so pollen in a core shows which plants grew at each time.
- More warm-climate species and fewer cool-climate species indicate warming.
5Dendrochronology
- Dendrochronology tree ring width records growth each year, as rings are wider in warm years.
- A light ring (fast spring and summer growth) and a dark ring (slow autumn growth) make one year.
- Cores from old trees go back hundreds of years.
6Correlation and causation
- Correlation and causation correlation alone does not prove causation, but together with the known action of greenhouse gases it forms strong evidence.
Part 2 of 9Greenhouse gases and the enhanced greenhouse effect
Greenhouse gases and the enhanced greenhouse effect
Greenhouse effect
- Greenhouse effect greenhouse gases absorb infrared radiation re-emitted from the Earth's surface and trap it in the atmosphere.
- The natural effect keeps Earth warm enough for life, as without it temperatures would fluctuate dramatically, as on Mars.
Enhanced (anthropogenic) greenhouse effect
- Enhanced (anthropogenic) greenhouse effect human activities raise greenhouse gas concentrations, so more infrared radiation is trapped.
Carbon dioxide
- Carbon dioxide it is released by burning fossil fuels since the industrial revolution, and by damage to carbon sinks.
- Sinks include trees, soils, peat bogs and the oceans.
- Deforestation, soil degradation, peat harvesting and ocean warming add CO2.
- CO2 rose from about 280 ppm pre-industrial to above 420 ppm.
- Seasonal fluctuationCO2 is lower in northern summer (more photosynthesis) and higher in winter.
Methane
- Methane a hydrocarbon (CH4), the main component of natural gas.
- Sources are ruminants such as cattle, landfill sites, fossil fuel extraction and anaerobic bacteria in rice paddies.
- Warming melts permafrost (ground frozen all year), which releases methane.
Terms
- Terms the greenhouse effect is natural, global warming is the rise in temperature,
- and climate change covers long-term changes in temperature, rainfall and wind.
Part 3 of 9The carbon cycle and reducing emissions
1
Carbon cycle
- Carbon cycle the transfer and storage of carbon between pools by fluxes.
- (atmosphere, biomass, oceans, soils, peat, fossil fuels)
- Photosynthesis removes CO2 from the atmosphere, and carbon is passed to consumers by feeding.
- Respiration by plants, animals and decomposers returns CO2.
- CO2 dissolves in the oceans and is used by marine plants and by organisms building calcium carbonate skeletons.
- Incompletely decomposed tissue forms peat or fossil fuels over millions of years, and burning peat, fossil fuels and wood returns carbon.
- Combustion of methane: CH4 + 2O2 → CO2 + 2H2O.
2
Management
- Management reduce entry points and increase removal.
- Reduce combustion of fossil fuels and biomass, and reduce disturbance of soils and peat bogs.
- Increase photosynthesis by planting trees.
Part 4 of 9Models and predictions
Extrapolation
- Extrapolation existing data are extended to predict future temperatures, used to plan flood defences, fund research and encourage reduced fossil fuel use, more renewables and less meat.
IPCC scenarios
- IPCC scenarios immediate cuts in fossil fuel use could limit warming to about 2 °C above pre-industrial levels, whereas no change could exceed 4 °C.
Limitations
- Limitations the emissions scenario that will occur is unknown, as is the success of future carbon capture.
- The exact effect of gas concentrations on temperature is uncertain and climate patterns are complex.
- A tipping point, such as methane from melting permafrost, could suddenly accelerate warming.
- Other factors, such as a volcanic eruption cooling the Earth with ash, are unpredictable.
Calculations
- Calculations percentage change = ÷ original value × 100, and rate of change is change in y ÷ change in x, for example ppm per year.
- (new value − original value)
Part 5 of 9Effects of climate change on species
Climate patterns
- Climate patterns extreme weather, changes in ocean currents and altered rainfall.
- (such as the Gulf Stream)
Distribution
- Distribution animals move towards the poles or to higher altitudes.
- They may out-compete or be out-competed by resident species, reducing biodiversity.
- Plants may be unable to move fast enough and may go extinct.
Water availability
- Water availability species relying on seasonal rains, such as some desert plants, may migrate or go extinct if rain becomes rarer.
Seasonal cycles
- Seasonal cycles plants flower earlier and animals breed earlier, so migrating birds may arrive when food is not available.
Ice and sea level
- Ice and sea level polar ice and glaciers retreat, mountain water supplies are threatened, and sea levels rise from thermal expansion and melting ice.
Part 6 of 9Practical: temperature and development
1Aim
- Aim laboratory work removes other factors such as light and food, using seedlings or brine shrimp.
2
Seedling growth rate
1
Plant seeds of one variety in pots of compost and allow them to germinate.
2
Measure the initial height of every seedling.
3
Place pots in incubators at different temperatures for the same time, for example 5 days, keeping moisture, pH and light the same.
4
Measure final heights and calculate average growth rate = average change in height ÷ days.
- Brine shrimp hatching
1
Place equal numbers of eggs (for example 40) in water baths at different temperatures, in non-chlorinated water with 2 g salt per 100 cm³.
2
Keep egg age, pH, water volume and dissolved oxygen the same.
3
Count hatched shrimps at set intervals such as every 12 hours.
4Calculate hatching rate
Calculate hatching rate number hatched ÷ hours in the water bath.
1Result
- Result growth and hatching rates increase up to about 25 °C and then fall, probably as enzymes denature.
2Welfare
- Welfare handle shrimps gently, avoid dangerous temperatures, return hatchlings to a suitable environment and switch lamps off when not in use.
Part 7 of 9Evaluating claims and sustainable conservation
Consensus
- Consensus scientists agree that rising greenhouse gases cause global warming and that human activities cause the rise.
Evaluating claims
- Evaluating claims check whether a statement addresses all the evidence and whether data come from several independent studies with significant results.
- Check for bias from financial, political or emotional interest,
- such as oil companies, fossil-fuel economies, campaigners or renewable energy companies.
- Climate is complex, one weather event cannot be attributed to climate change, and a tipping point makes exact predictions difficult.
Biofuels
- Biofuels made from recently grown plants such as sugar cane and burned like fossil fuels.
- Foroften cheaper than oil, renewable and carbon neutral because the carbon was recently removed from the air.
- Againstthey still release CO2, need land that could grow food, can cause loss of habitats such as rainforest,
- and removing mature trees reduces photosynthesis.
Other renewables
- Other renewables wind, solar, geothermal and tidal energy release no CO2 in use and are becoming cheaper and more efficient.
- Each has limits: geothermal needs volcanic activity, solar needs sunshine, wind turbines affect birds, bats and landscape,
- and tidal energy is coastal only.
Carbon removal
- Carbon removal large-scale carbon capture technology does not yet exist, so photosynthesis is the main method.
- Stop deforestation and plant trees, since mature trees store carbon in their biomass and mature forests are close to carbon neutral.
- Costa Rica now plants seven times more trees than it cuts, helped by government payments to landowners.
Part 8 of 9More from the specification
1Mechanism of Natural Selection
- Within any biological population, random mutations generate phenotypic variation among individuals;
- environmental selection pressures favour those with advantageous characteristics, granting them higher reproductive fitness to pass advantageous alleles to subsequent generations.
2Changes in Allele Frequencies
- Over successive generations, natural selection causes the frequency of advantageous alleles to increase within the gene pool of populations,
- while non-adaptive traits decrease in frequency.
3Allopatric and Sympatric Speciation
- Speciation occurs when reproductive isolation prevents gene flow between divergent populations;
- geographic barriers (allopatric) or behavioural/temporal isolation (sympatric) allow distinct selection pressures and genetic drift to accumulate until interbreeding is impossible.
4Evolutionary Adaptation to Rapid Climate Shifts
- Changing climatic conditions exert strong directional selection pressures on animal and plant populations, threatening species that lack sufficient genetic diversity with population decline or extinction.
5Population
- All organisms of one species in an area.
6Allele
- An alternative form of a gene.
7Speciation
- Formation of new species from isolated populations.
8Natural selection
- Process in which better adapted organisms survive and reproduce more.
9Selection pressure
- An environmental factor that affects survival.
10Allele frequency
- How common an allele is in a population.
Part 9 of 9More on this topic
Evidence
- Evidence carbon-cycle measurements and long-term temperature records are separate lines of evidence interpreted together.
Climate models
- Climate models they test possible futures under stated scenarios, with uncertainty in the predictions.
Key terms
| Term | Meaning |
|---|---|
| Greenhouse gas | A gas that absorbs infrared radiation re-emitted from the Earth and traps it in the atmosphere. |
| Carbon sink | A store of carbon such as trees, soils, peat bogs and oceans. |
| Dendrochronology | Using tree ring widths to measure past climate. |
| Permafrost | Ground that stays frozen all year round. |
| Q10 | Temperature coefficient, the rate at a temperature divided by the rate 10 °C lower. |
| Biofuel | A fuel made from recently grown plant biomass. |
| Extrapolation | Extending existing data to predict future values. |
Avoid these mistakes
1
Using greenhouse effect, global warming and climate change interchangeably — they have different meanings.
2
Concluding that CO2 causes warming from correlation alone — the conclusion also rests on the known action of greenhouse gases.
3
Saying biofuels release no carbon dioxide — they release it, but it was recently removed from the atmosphere.
4
Forgetting to subtract the original value in a percentage change calculation.
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