Climate Change

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The Greenhouse Effect and Anthropogenic Climate Change

Radiation from the sun hits the Earth and is re-radiated back from the surface.
A greenhouse gas absorbs this re-radiated radiation, trapping it in the atmosphere so it is not lost to space.
Greenhouse gases act like the glass of a greenhouse, hence the term greenhouse effect.
The greenhouse effect is natural and keeps Earth warm enough for life; without it, Earth would have dramatic temperature fluctuations like Mars (20°C to −153°C).
Key greenhouse gases include carbon dioxide and methane.
Increasing levels of these gases from human activities lead to anthropogenic climate change.
Global warming refers to the rise in global temperatures mainly due to increasing greenhouse gas concentrations.
Climate change refers to long-term changes in climate measures such as precipitation, temperature, and wind patterns, often a consequence of global warming.

The greenhouse effect

Human Activities and Carbon Dioxide

Atmospheric carbon dioxide has fluctuated naturally due to volcanic eruptions and weathering of limestone.
Since the industrial revolution (late 1700s), atmospheric carbon dioxide has risen to its highest levels in Earth's history.
Fossil fuel combustion for factories, transport, and homes releases carbon dioxide.
A clear correlation exists between increasing carbon dioxide since the industrial revolution and increasing global temperatures.
Correlation alone does not prove causation, but combined with knowledge of greenhouse gases it provides strong evidence.
Carbon dioxide is also released when natural carbon stores (carbon sinks) are damaged; sinks include trees, soils, peat bogs, and oceans.
Deforestation, soil degradation, peat harvesting, and ocean warming all add carbon dioxide to the atmosphere.

Human Activities and Methane

Methane (CH₄) is a simple hydrocarbon and the main component of natural gas.
Methane is produced by some bacteria naturally, but levels have risen significantly in the last 150 years due to human activities.
Methane is released from the guts of ruminant mammals such as cattle; intensive farming has greatly increased this contribution.
Landfill sites release methane when organic matter decomposes.
Extraction of fossil fuels from underground releases methane.
Anaerobic bacteria in waterlogged rice paddy fields release methane.
Warming of the poles releases methane from natural stores such as permafrost (ground frozen all year round).

Correlation, Causation, and Positive Feedback

Positive correlation: as one variable increases, the other also increases; negative correlation: as one increases, the other decreases.
Antarctic ice cores show a positive correlation between global temperatures and atmospheric carbon dioxide over hundreds of thousands of years.
Correlation does not prove causation; it is not possible to say which variable influenced the other, and an unknown third variable might be involved.
Positive feedback is a mechanism that leads to additional change away from equilibrium, amplifying deviation and driving systems towards a tipping point.
Global warming has a positive feedback effect: warming leads to more warming.

Positive Feedback Mechanisms

Albedo is the extent to which a surface reflects light; snow and ice have high albedo, while rock and soil have low albedo.
As polar ice melts, Earth's overall albedo decreases, so more solar energy is absorbed by exposed rock, soil, and dark ocean, increasing global warming.
Decomposition by bacteria and fungi occurs faster at higher temperatures, releasing more carbon dioxide.
Increased decomposition in peat bogs and permafrost releases huge volumes of carbon dioxide.
Permafrost is a huge carbon sink because organic material cannot decompose at low temperatures; decay organisms are inactive when frozen.
Melting permafrost leads to release of methane due to methanogenic microorganisms (archaea) in the soil.
Global warming increases droughts, making wildfires more likely; combustion of plants releases carbon dioxide and reduces photosynthesis, so less carbon dioxide is removed.

Impact of Climate Change: Boreal Forests

Boreal forests (taiga) cover much of North America, Europe, and Russia and are an important carbon sink due to their size.
Global warming can cause boreal forests to switch from a carbon sink to a carbon source, known as a tipping point.
Reduced snow leads to less snowmelt water, causing drought and reducing photosynthesis in coniferous trees.
Lack of water causes loss of green pigment (forest browning), and eventually trees die.
Dead trees dry out and the risk of forest fires increases.
Legacy carbon combustion releases carbon locked up for many years in living trees, dead needles, and soil.
This can tip forests from carbon sink to source, and the change can be irreversible.

Impact of Climate Change: Polar Habitats and Ocean Currents

Many species rely on polar ice; sea ice forms when the ocean freezes, and landfast ice is attached to land.
Global warming means less sea ice and earlier break-up, causing problems for breeding animals.
Emperor penguins breed on Antarctic sea ice; early melting does not give them enough time to raise young.
Walruses rely on Arctic sea ice; early loss means nursing mothers must care for young further from the water's edge.
Ocean currents redistribute heat; warm currents like the Gulf Stream moderate coastal temperatures (e.g. Europe warmer than Canada at similar latitude).
Upwelling brings cold, nutrient-rich water to the surface, supporting marine life and fisheries.
El Niño events involve warming of the central Pacific, preventing nutrient upwelling off Central and South America, reducing primary production and causing extreme weather.

Impact of Climate Change: Range Shifts and Coral Reefs

Species have tolerance limits; if conditions change beyond these, they must migrate or face extinction.
Migration may be a poleward shift (towards poles) or an upslope shift (to higher altitude).
Montane bird species in Papua New Guinea have moved upslope by an average of more than 100 m over 50 years.
North American tree species show range contraction and northward spread.
Coral reefs are built by reef-building corals (polyps) that live symbiotically with algae; algae provide carbon compounds and coral provides shelter.
Around 25% of ocean fish species depend on coral reefs.
Corals are sensitive to temperature and pH; warming causes polyps to expel algae, leading to coral bleaching and death.
Ocean acidification weakens calcium carbonate exoskeletons and reduces carbonate ion availability for building hard parts.

Ocean Acidification

The oceans dissolve huge amounts of carbon dioxide, forming carbonic acid (H₂CO₃): CO₂ + H₂O → H₂CO₃.
Carbonic acid dissociates to hydrogen ions (H⁺) and hydrogen carbonate ions (HCO₃⁻): H₂CO₃ → H⁺ + HCO₃⁻.
Hydrogen carbonate ions can dissociate further to more H⁺ and carbonate ions (CO₃²⁻): HCO₃⁻ → H⁺ + CO₃²⁻.
Normally this keeps oceans slightly alkaline and supplies carbonate ions for organisms.
As atmospheric carbon dioxide increases, more dissolves, more H⁺ is produced, and the ocean becomes more acidic (ocean acidification).
Oceans remain alkaline but pH has decreased, moving closer to neutral.
The reaction H⁺ + CO₃²⁻ → HCO₃⁻ reverses to buffer H⁺, reducing carbonate ions available for calcium carbonate exoskeletons.
Note: ocean acidification shares the same cause as global warming (increased atmospheric carbon dioxide) but is not a direct result of global warming.

Carbon Sequestration

Carbon sequestration is the process of capturing and storing carbon dioxide from the atmosphere.
It can be increased by removing carbon into natural carbon sinks; artificial storage is still at the research stage.
Forest regeneration (reforestation) involves planting new trees in deforested areas; afforestation is creating new forests.
Mature trees store huge amounts of carbon in their biomass; e.g. Costa Rica plants seven times more trees than it cuts down.
Peat bog restoration: peat bogs form when plant matter cannot fully decompose due to waterlogged, acidic conditions, storing carbon.
Draining peat bogs for fuel, development, or agriculture increases decay organism activity and releases carbon dioxide.
Filling in drainage ditches and regulating peat harvesting allows peat bogs to recover and sequester carbon.
Scientists debate whether planting fast-growing non-native trees or rewilding with native species is best; non-native trees sequester carbon faster, but rewilding may benefit biodiversity more.

The carbon cycle

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1.Which process results in the production of methane gas?
Easy
- ACombustion of fossil fuels
- BLivestock farming
- CDeforestation
- DOcean acidification
2.How does climate change affect boreal forests? I. A change from net carbon loss to net carbon accumulation. II. An increase in drought. III. A decrease in legacy carbon combustion.
Easy
- AI and II only
- BII only
- CI, II and III
- DII and III only
3.A climate change sceptic made the following statement: 'There is no consensus amongst scientists that climate change is real, global warming is a natural and normal phenomenon which has occurred at other points in history'. Which of the following opposes the idea that global warming is a natural phenomenon?
Medium
- AThe idea that many factors contribute towards global climate
- BData produced by companies involved in global fossil fuel supply shows decreasing greenhouse gas production
- CScientific research which links the combustion of fossil fuels with global warming
- DPublished data which shows that rates of global warming have not been consistent over the last 50 years
4.How does peat drainage lead to an increased warming effect?
Medium
- ADrainage allows saprotroph activity to increase, releasing carbon dioxide when the organic matter stored in the peat is broken down.
- BWater seals the stored carbon dioxide underground, so the loss of water allows the gas to escape.
- CThe removal of water from the peatland allows herbivores to move in and consume the vegetation growing on the peat bog, eventually leading to the release of carbon stored in the vegetation into the atmosphere.
- DDrained land can be used for crop growth, removing carbon from the soil.
5.Different greenhouse gases have different global warming potential, or GWP. Gas | GWP over 100 years Carbon dioxide | 1 Methane | 21 Nitrous oxide | 310 Sulfur hexafluoride | 23,900 Which factors contribute to the global warming potential of greenhouse gases?
Medium
- AAtmospheric concentration only.
- BAtmospheric concentration and ability to absorb radiation.
- CAtmospheric concentration, ability to absorb radiation, and atmospheric lifetime.
- DAbility to absorb radiation only.
6.Which of the following are impacts of global warming? I. Increased UV radiation reaching earth due to depletion of ozone gas in the atmosphere II. Ocean acidification III. An increase in the number of extreme weather events
Medium
- AI and II only
- BII and III only
- CIII only
- DI, II, and III
7.The pH content of a water body in Australia was measured over a 10 year period. Scientists are concerned about the general downward trend of the data, which shows less alkali conditions than is characteristic. Which of the statements suggests why the scientists may have cause for concern? I. Decreased rates of photosynthesis may occur at low pH II. Decreasing pH increases calcium carbonate solubility III. Some species of algae thrive in extreme pH levels
Hard
- AI and II only
- BII and III only
- CNone of the above
- DII only
8.The greenhouse effect is a naturally occurring process that is essential for keeping Earth warm enough for life.
Easy
True or false?

Soal lainnya

9.Ocean acidification is a direct result of global warming.
Easy
True or false?
10.Which of the following is the best definition of carbon sequestration?
Easy
- AThe release of carbon dioxide from fossil fuels
- BThe process of capturing and storing carbon dioxide from the atmosphere
- CThe breakdown of organic matter by decomposers
- DThe movement of carbon dioxide from the atmosphere into the ocean
11.Which of the following is a carbon sink?
Easy
- APeat bogs
- BFactories
- CVolcanoes
- DCattle
12.Which human activity directly releases methane into the atmosphere?
Medium
- ABurning coal in power stations
- BDraining peat bogs for agriculture
- CKeeping ruminant livestock such as cattle
- DCutting down tropical rainforest
13.What is the name of the process by which increased global temperatures cause more global warming, which in turn causes further warming?
Medium
- ANegative feedback
- BPositive feedback
- CCarbon sequestration
- DOcean acidification
14.Which of the following best explains why melting polar ice increases global warming?
Medium
- AIce has a low albedo, so melting it increases reflection of sunlight.
- BIce has a high albedo, so melting it decreases reflection and more energy is absorbed.
- CMelting ice releases carbon dioxide directly into the atmosphere.
- DMelting ice increases the salinity of the ocean, which traps heat.
15.Which of the following are greenhouse gases? (select all that apply)
Medium
- ACarbon dioxide
- BMethane
- COxygen
- DNitrogen
- EWater vapour
16.Which of the following are impacts of increasing average global temperatures? (select all that apply)
Medium
- ARising sea levels due to melting ice
- BMore frequent extreme weather events
- CIncreased ocean acidity
- DCoral bleaching
- EIncreased ozone depletion
17.Methane is a more potent greenhouse gas than carbon dioxide over a 100-year period.
Easy
True or false?
18.A correlation between two variables proves that one variable causes the other.
Easy
True or false?
19.Match each greenhouse gas with its global warming potential (GWP) over 100 years.
Medium
- Carbon dioxide
- Methane
- Nitrous oxide
- Sulfur hexafluoride
- 1
- 21
- 310
- 23,900
20.Place the following steps of ocean acidification in the correct order.
Medium
- Carbon dioxide dissolves in seawater
- Carbonic acid forms
- Carbonic acid dissociates to release hydrogen ions
- Hydrogen ions increase, lowering pH
21.Which type of radiation is mainly absorbed by greenhouse gases to produce the greenhouse effect?
Medium
- AShortwave radiation coming from the Sun
- BLongwave radiation re-emitted by the Earth's surface
- CUltraviolet radiation from the Sun
- DVisible light reflected by clouds
22.Which of the following are carbon sinks? (select all that apply)
Medium
- APeat bogs
- BThe oceans
- CVolcanic eruptions
- DForests
- EFossil fuel combustion
23.Match each term with its correct definition.
Medium
- Albedo
- Permafrost
- Carbon sink
- Positive feedback
- Ground that remains frozen all year round
- A store that removes carbon dioxide from the atmosphere
- A mechanism that amplifies change away from equilibrium
- The extent to which a surface reflects light
24.Place the following stages of the positive feedback cycle caused by melting polar ice in the correct order.
Medium
- Global temperatures increase
- Polar ice melts, reducing the Earth's albedo
- More solar energy is absorbed by exposed rock, soil and ocean
- Global warming is further increased
25.Which human activities contribute to increased atmospheric methane? (select all that apply)
Medium
- AIntensive farming of ruminant mammals
- BDecomposition of organic matter in landfill sites
- CExtraction of fossil fuels from underground
- DAnaerobic bacteria in waterlogged rice paddy fields
- EWeathering of limestone rocks
26.What is the correct definition of carbon sequestration?
Medium
- AThe release of carbon dioxide from fossil fuel combustion
- BThe process of capturing and storing carbon dioxide from the atmosphere
- CThe breakdown of organic matter by decomposers
- DThe movement of carbon dioxide from the atmosphere into the oceans
27.Which of the following is an example of a carbon sink?
Medium
- AA factory burning coal
- BA peat bog
- CA volcanic eruption
- DA car exhaust
28.Which of the following statements about correlation and causation in climate science are correct? (select all that apply)
Hard
- AA positive correlation means that as one variable increases, the other also increases.
- BA correlation alone proves that one variable causes the other.
- CEvidence from Antarctic ice cores shows a positive correlation between global temperatures and atmospheric carbon dioxide.
- DAn unknown third variable might be involved in a correlation.
- EA negative correlation means that as one variable increases, the other also increases.
29.Which of the following are consequences of ocean acidification? (select all that apply)
Hard
- ACalcium carbonate exoskeletons of corals can weaken or dissolve.
- BThe availability of carbonate ions for building hard exoskeletons is reduced.
- CThe oceans become more alkaline.
- DThe pH of seawater decreases, moving it closer to neutral.
- EThe oceans become more acidic than neutral.
30.Which statements describe likely consequences of the pH change? I. Decreased rates of photosynthesis in some aquatic producers. II. Increased solubility of calcium carbonate. III. Increased growth of algae that require alkaline conditions.
Hard
- AI and II only
- BII and III only
- CI and III only
- DI, II and III
31.Two identical seashells were placed in saltwater for 45 days. Shell A was kept at pH 8.5 and shell B at pH 7.0. After 45 days, shell B had lost noticeably more mass and its surface was pitted. Which conclusion is best supported?
Hard
- AShell B dissolved faster because lower pH increases the solubility of calcium carbonate.
- BShell B dissolved faster because lower pH increases the availability of carbonate ions.
- CShell A dissolved faster because higher pH increases the solubility of calcium carbonate.
- DThe difference is due to temperature, not pH.
32.A student investigates the effect of temperature on decomposition in a peat bog. Four sealed samples of peat are kept at 5°C, 15°C, 25°C and 35°C for 30 days. The carbon dioxide concentration in each container is measured at the end. Which result would best support the idea that decomposition accelerates global warming?
Medium
- ACarbon dioxide concentration decreases as temperature increases.
- BCarbon dioxide concentration increases as temperature increases.
- CCarbon dioxide concentration is the same at all temperatures.
- DCarbon dioxide concentration is highest at 5°C.
33.A satellite measures the albedo of a polar region over 20 years. The albedo falls from 0.80 to 0.55 as ice melts and exposes dark ocean and rock. Which sequence best explains the effect of this change?
Hard
- ALess solar energy is absorbed, so global warming slows.
- BMore solar energy is absorbed, so global warming increases.
- CMore solar energy is reflected, so global warming increases.
- DAlbedo has no effect on global temperature.
34.A marine food web depends on upwelling of nutrient-rich water off the coast of South America. During an El Niño event, warm surface water prevents upwelling. Which outcome is most likely?
Hard
- APrimary production increases, supporting more fish.
- BPrimary production decreases, reducing energy flow through the food web.
- CUpwelling increases, bringing more nutrients to the surface.
- DOcean pH rises, benefiting reef-building corals.
35.A population of montane birds has been monitored on a tropical mountain for 50 years. The upper elevation limit of most species has risen by an average of more than 100 m, while a few species have moved downslope. Which explanation best fits these data?
Challenge
- AMost species are tracking cooler temperatures upslope; a few are limited by other factors.
- BMost species are moving towards the poles; a few are moving to higher altitude.
- CAll species are moving upslope because oxygen availability increases with altitude.
- DThe birds are moving downslope because temperatures are falling.
36.A student reads that a correlation between two variables does not prove causation. Which statements about correlation and causation in climate science are correct? (select all that apply)
Hard
- AA positive correlation means that as one variable increases, the other also increases.
- BA negative correlation means that as one variable increases, the other decreases.
- CA correlation alone proves that one variable causes the other.
- DIt is possible that an unknown third variable is involved in a correlation.
- ECorrelation analysis involves measuring two variables and assessing their relationship.
37.A negative correlation means that as one variable increases, the other variable also increases.
Easy
True or false?
38.Upwelling brings cold, nutrient-rich water to the surface, supporting marine life.
Easy
True or false?
39.Match each term with its correct description.
Medium
- Albedo
- Upwelling
- Permafrost
- Carbon sink
- The proportion of light reflected by a surface
- The rise of cold, nutrient-rich water to the ocean surface
- Ground that remains frozen all year round
- A store that removes carbon dioxide from the atmosphere
40.A study compares two lakes. Lake X has a pH of 8.1 and Lake Y has a pH of 7.6. Both contain the same species of shelled invertebrate. After 60 days, the shells in Lake Y are thinner and more porous. Which explanation is most consistent with the data?
Challenge
- ALake Y has more carbonate ions available for shell building.
- BLake Y has more hydrogen ions, increasing calcium carbonate solubility.
- CLake X has more hydrogen ions, increasing calcium carbonate solubility.
- DThe difference is due to temperature, not pH.
41.Complete the sentence about the greenhouse effect.
Easy
Greenhouse gases absorb radiation that is re-emitted from the Earth's ____.
42.Complete the sentence about methane sources.
Medium
Methane is released from the guts of ____ mammals, such as cattle, that are farmed by humans.
43.Complete the sentence about carbon sequestration.
Medium
Carbon sequestration can be defined as the process of capturing and storing ____ from the atmosphere.
44.Methane is released from wetlands at a rate of 150 Tg year⁻¹ and from other sources at 250 Tg year⁻¹. Calculate the total amount of methane released per year, in Tg year⁻¹.
Hard
45.What is the term for the process by which increased atmospheric carbon dioxide causes the pH of seawater to decrease?
Medium
46.What is the name of the ground that remains frozen all year round and acts as a large carbon sink?
Easy
47.What is the term for the measure of how much light a surface reflects?
Medium
48.Complete the sentence about ocean acidification using the correct chemical species.
Medium
Carbon dioxide reacts with water to form carbonic acid, which dissociates to release hydrogen ions and ____ ions.
49.Complete the sentence about the effect of ocean acidification on marine organisms.
Medium
Increasing hydrogen ion concentration in seawater reduces the availability of ____ ions needed by corals to build calcium carbonate exoskeletons.
50.A study estimates that wetlands release 150 Tg of methane per year and other sources release 250 Tg per year. Calculate the total methane released per year, in Tg year⁻¹.
Hard
51.A peat bog stores 800 tonnes of carbon per hectare. Draining it causes 12% of this stored carbon to be released as carbon dioxide over 10 years. Calculate the mass of carbon released per hectare over this period, in tonnes.
Hard
52.Name the process by which cold, nutrient-rich water rises to the surface of the ocean, supporting marine life.
Medium
53.Outline the way in which atmospheric carbon dioxide affects the pH of oceans and how this change may impact marine organisms.
Hard
54.Outline the impacts of increasing average global temperatures.
Hard
55.Describe conservation approaches that aid carbon sequestration.
Hard
56.Suggest the possible impact that an increase in global temperatures would have on the polar regions, as well as the global consequences of this impact.
Hard
57.Methane is released from wetlands at a rate of 150 Tg year⁻¹ and from other sources at 250 Tg year⁻¹. Calculate the total amount of methane released per year, in Tg year⁻¹.
Hard
- A360 Tg year⁻¹
- B440 Tg year⁻¹
- C480 Tg year⁻¹
- D400 Tg year⁻¹
58.A study estimates that wetlands release 150 Tg of methane per year and other sources release 250 Tg per year. Calculate the total methane released per year, in Tg year⁻¹.
Hard
- A440 Tg year⁻¹
- B400 Tg year⁻¹
- C480 Tg year⁻¹
- D360 Tg year⁻¹
59.A peat bog stores 800 tonnes of carbon per hectare. Draining it causes 12% of this stored carbon to be released as carbon dioxide over 10 years. Calculate the mass of carbon released per hectare over this period, in tonnes.
Hard
- A86 tonnes
- B106 tonnes
- C116 tonnes
- D96 tonnes

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