The big idea: A warming climate changes the physical world and natural ecosystems, not just people.
The main physical and environmental impacts are:
- Rising sea levels — coasts flood and erode. - Melting ice and falling albedo — bright ice that reflected sunlight is lost. - Shifting biomes — habitats and species move towards the poles or uphill. - More extreme weather — heatwaves, droughts, storms and floods become more common.
Key terms
- Climate change — a long-term shift in temperature and weather patterns, driven mainly by greenhouse-gas warming.
- Temperature anomaly — how much warmer or cooler a place is than its long-term average (e.g. +12C means 12C above normal).
- Albedo — how much sunlight a surface reflects; bright ice and snow have high albedo, dark ocean and land have low albedo.
- Biome — a large natural region defined by its climate, plants and animals (e.g. tundra, forest, desert).
- Sea-level rise — the rise in average ocean height as the planet warms.
Physical impacts come first: This micro is about impacts on environmental systems (oceans, ice, biomes, weather).
The impacts on people and health are tested in the next micro — keep the two separate in an answer.
A good answer names the impact, then explains the mechanism — the chain of cause and effect that links warming to the result.
| Impact | Mechanism (why it happens) |
|---|---|
| Sea-level rise | Warmer ocean water expands (thermal expansion) AND melting land ice adds water |
| Falling albedo | Bright ice melts and exposes dark ocean/land, which absorbs more heat and warms faster |
| Shifting biomes | As temperature belts move polewards/uphill, the climate a species needs moves too |
| More extreme weather | A warmer atmosphere holds more energy and moisture, fuelling stronger heatwaves and storms |
Albedo is a feedback loop: Melting ice lowers albedo, so the dark surface absorbs more heat, which melts more ice.
This self-reinforcing chain is a positive feedback loop — it speeds warming up.
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Biomes shift polewards and uphill: As a region warms, the biome suited to the old climate moves.
Example: North American forests such as the oak-hickory belt are projected to shift northwards by 2100 as the climate that suits them moves towards the poles — and some southern edges are lost to it becoming too warm and dry.
Animal migration changes: Warming changes when and where animals move.
Example: many birds now migrate earlier in spring because warmer temperatures arrive sooner, and some species shift their whole range polewards to stay in the climate and food supply they need.
Oceans and shipping routes: Melting Arctic sea ice is opening new shipping routes (e.g. the Northern Sea Route) for part of the year, shortening journeys between Europe and Asia.
But warming also brings more storms and unpredictable ice, which can disrupt routes and raise risk.
How to turn a biome/species impact into marks
- Name the impact (the biome shifts north).
- Give the mechanism — the warming moves the climate belt the species needs.
- Add a named example (oak-hickory forest, Arctic shipping) for top marks.
How this is tested: Paper 2 Q2 on global climate usually opens with a map, infographic or graph — a temperature-anomaly map, a biome-projection map, a heatwave map or a flood-events graph.
You Identify a value or region, then Describe the pattern or trend. The unit often finishes with a [10] 'to what extent' essay weighing environmental against human impacts.
| Year | Number of major flood events |
|---|---|
| 1980 | 30 |
| 1990 | 90 |
| 2000 | 150 |
| 2010 | 210 |
| 2019 | 260 |
IB-style question — read the graph
Using the flood-events table above: (a) identify the number of flood events in the year 2000 [1]; (b) describe how the number of flood events changes over the period [2].
How to answer each part
- (a) Identify the value. Read the row for 2000 -> 150 flood events. Quote the figure exactly.
- (b) Describe the trend. State the direction (a steady increase) and support it with figures -- the number rises from 30 in 1980 to 260 in 2019, roughly a nine-fold rise.
Final answer
(a) 150 events; (b) a clear upward trend, rising steadily from 30 (1980) to 260 (2019).
The [10] essay: environment vs human impacts: A common [10] asks: to what extent does climate change affect environmental systems more than human societies?
Use a For / Against / Judgement structure, anchored to named examples — the answer-plan below shows the shape.