SL Content Statements

• D4.3.1

  Anthropogenic causes of climate change
  

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  Limit to anthropogenic increases in atmospheric concentrations of carbon dioxide and methane.
  NOS: Students should be able to distinguish between positive and negative correlation and should also distinguish between correlation and causation. For example, data from Antarctic ice cores shows a positive correlation between global temperatures and atmospheric carbon dioxide concentrations over hundreds of thousands of years. This correlation does not prove that carbon dioxide in the atmosphere increases global temperatures, although other evidence confirms the causal link.
  

• D4.3.2

  Positive feedback cycles in global warming

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  Include release of carbon dioxide from deep ocean, increases in absorption of solar radiation due to loss of reflective snow and ice, accelerating rates of decomposition of peat and previously undecomposed organic matter in permafrost, release of methane from melting permafrost and increases in droughts and forest fires.
  

• D4.3.3

  Change from net carbon accumulation to net loss in boreal forests as an example of a tipping point

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  Include warmer temperatures and decreased winter snowfall leading to increased incidence of drought and reductions in primary production in taiga, with forest browning and increases in the frequency and intensity of forest fires, which result in legacy carbon combustion.
  

• D4.3.4

  Melting of landfast ice and sea ice as examples of polar habitat change

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  Include potential loss of breeding grounds of the emperor penguin (Aptenodytes forsteri) due to early breakout of landfast ice in the Antarctic and loss of sea ice habitat for walruses in the Arctic.
  

• D4.3.5

  Changes in ocean currents altering the timing and extent of nutrient upwelling
  

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  Warmer surface water can prevent nutrient upwelling to the surface, decreasing ocean primary production and energy flow through marine food chains.
  

• D4.3.6

  Poleward and upslope range shifts of temperate species
  

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  As evidence-based examples, include upslope range shifts for tropical-zone montane bird species in New Guinea and range contraction and northward spread in North American tree species.
  

• D4.3.7

  Threats to coral reefs as an example of potential ecosystem collapse
  

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  Increased carbon dioxide concentrations are the cause of ocean acidification and suppression of calcification in corals. Increases in water temperature are a cause of coral bleaching. Loss of corals causes the collapse of reef ecosystems.
  

• D4.3.8

  Afforestation, forest regeneration and restoration of peat-forming wetlands as approaches to carbon sequestration
  

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  NOS: There is active scientific debate over whether plantations of non-native tree species or rewilding with native species offer the best approach to carbon sequestration. Peat formation naturally occurs in waterlogged soils in temperate and boreal zones and also very rapidly in some tropical ecosystems.
  

AHL Content Statements

• D4.3.9

  Phenology as research into the timing of biological events
  

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  Students should be aware that photoperiod and temperature patterns are examples of variables that influence the timing of biological events such as flowering, budburst and bud set in deciduous trees, bird migration and nesting.
  

• D4.3.10

  Disruption to the synchrony of phenological events by climate change

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  Students should recognize that within an ecosystem temperature may act as the cue in one population and photoperiod may be the cue in another. Include spring growth of the Arctic mouse-ear chickweed (Cerastium arcticum) and arrival of migrating reindeer (Rangifer tarandus) as one example. Also include a suitable local example or use the breeding of the great tit (Parus major) and peak biomass of caterpillars in north European forests as another.
  

• D4.3.11

  Increases to the number of insect life cycles within a year due to climate change

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  Use the spruce bark beetle (Ips typographus or Dendroctonus micans) as an example.
  

• D4.3.12

  Evolution as a consequence of climate change

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  Include changes in the fitness of colour variants of the tawny owl (Strix aluco) as a consequence of changes in snow cover.