2.4 Climate and Biomes

Guiding questions

How does climate determine the distribution of natural systems?
How are changes in Earth systems affecting the distribution of biomes?

SL and HL knowledge statements

2.4.1 Climate describes atmospheric conditions over relatively long periods of time, whereas weather describes the conditions in the atmosphere over a short period of time.

2.4.2 A biome is a group of comparable ecosystems that have developed in similar climatic conditions, wherever they occur.

I recommend you watch this informative video at 1.25x or 1.5x speed. It’s clear and easy to understand, but the narration is slow.

2.4.3 Abiotic factors are the determinants of terrestrial biome distribution.

2.4.4 Biomes can be categorized into groups that include freshwater, marine, forest, grassland, desert and tundra. Each of these groups has characteristic abiotic limiting factors, productivity and diversity. They may be further classed into many subcategories (for example, temperate forests, tropical rainforests and boreal forests).

2.4.5 The tricellular model of atmospheric circulation explains the behaviour of atmospheric systems and the distribution of precipitation and temperature at different latitudes. It also explains how these factors influence the structure and relative productivity of different terrestrial biomes.

2.4.6 The oceans absorb solar radiation and ocean currents distribute the resulting heat around the world.

This video spells out exactly how warm and cold ocean currents influence regional climate patterns. It’s simple, yet effective.

2.4.7 Global warming is leading to changing climates and shifts in biomes.

Climate change impacts our oceans, which in turn influence regional and global climate patterns – another example of feedback mechanisms in ecosystems.

Knowledge statements for HL only

2.4.8 There are three general patterns of climate types that are connected to biome types.

2.4.9 The biome predicted by any given temperature and rainfall pattern may not develop in an area because of secondary influences or human interventions.

2.4.10 The El Niño Southern Oscillation (ENSO) cycle is the fluctuation in wind and sea surface temperatures that characterizes conditions in the tropical Pacific Ocean. The two opposite and extreme states are El Niño and La Niña, with transitional and neutral states between the extremes.

I like this explanation of El Niño and ENSO because the host, Amit Sengupta, breaks it down into simple, distinct steps and then connects them.

2.4.11 El Niño is due to a weakening or reversal of the normal east–west (Walker) circulation, which increases surface stratification and decreases upwelling of cold, nutrient-rich water near the coast of north-western South America. La Niña is due to a strengthening of the Walker circulation and reversal of other effects of El Niño.

Here’s another clear explanation of El Niño, connecting events in the atmosphere with oceanic phenomena that, in turn, influence atmospheric systems.

2.4.12 Tropical cyclones are rapidly circulating storm systems with a low-pressure centre that originate in the tropics and are characterized by strong winds.

2.4.13 Rises in ocean temperatures resulting from global warming are increasing the intensity and frequency of hurricanes and typhoons because warmer water and air have more energy.

According to the NOAA, “New research indicates that the number of tropical cyclones has been rising since 1980 in the North Atlantic and Central Pacific.”

Image: NASA/NOAA

Practical activities

2.4.3 Application of skills: Create climate graphs showing annual precipitation/average temperature for different biomes.
2.4.5 Application of skills: Link the tricellular model of atmospheric circulation to the planetary distribution of heat and biomes.
Add from existing PSOW booklet.

Possible engagement opportunities

from official syllabus. Turn into CAS suggestions connected to UN SDGs.

Happy learning!