Assessing the rate and extent of climate change requires diverse data sources — both direct measurements and model outputs — across local, regional and global scales. VCE Environmental Science focuses on four key indicators: global average temperatures, local climate extremes, sea level rise and snow and ice coverage.
| Type | Description | Strengths | Limitations |
|---|---|---|---|
| Direct measurements | Instrumental records from weather stations, ships, buoys, satellites | High precision and accuracy | Limited spatial and temporal coverage in historical period |
| Climate modelling | Computer simulations (General Circulation Models) that reproduce past climate and project future scenarios | Global coverage; can test ‘what if’ scenarios | Model uncertainty; rely on assumptions |
| Proxy records | Indirect biological/geological indicators (ice cores, tree rings, corals) | Extend record back thousands of years | Lower precision; calibration required |
Source: Combined land surface and sea surface temperature (SST) datasets maintained by CSIRO/BoM (Australia), NOAA, NASA, UK Met Office Hadley Centre.
Key findings:
- Global average surface temperature increased ~1.1°C above pre-industrial (1850–1900) levels by 2024
- Warming has accelerated — the past decade (2014–2023) is the warmest on record
- Land areas have warmed faster than oceans; Arctic regions ~4× the global average rate
Model projections (IPCC AR6, 2021):
- If global emissions reach net zero by ~2050 (low emissions scenario, SSP1-1.9): limit warming to ~1.5°C
- Business-as-usual (high emissions scenario, SSP5-8.5): 3.3–5.7°C warming by 2100
What is measured:
- Frequency and intensity of heatwaves (days above extreme heat threshold)
- Duration and severity of droughts
- Intensity of extreme rainfall events
- Number of days of very high fire danger
Australian context:
- Australia has warmed by ~1.47°C since 1910
- Extreme heat events have become more frequent and severe
- Southern Australia experiencing long-term drying trend (reduced autumn-winter rainfall)
- Tropical north experiencing intensification of extreme rainfall events
- Black Summer (2019–20): Record fire weather conditions — ~18.6 million hectares burned
Local climate extremes data sources:
- BoM (Bureau of Meteorology): Weather station records dating back to ~1900 in many locations
- Long-term rainfall and temperature trends for every Australian location available at climate.bom.gov.au
Sources:
- Tide gauges: Continuous records at coastal locations; some extend back to early 19th century
- Satellite altimetry (TOPEX/Poseidon, Jason series, Sentinel-6): Near-global sea level since 1992; precision of ~1–2 cm
Key findings:
- Global mean sea level (GMSL) rose ~20 cm between 1900 and 2018
- Rate of rise has accelerated: currently ~3.6 mm/year
- Main contributors: thermal expansion of warming ocean (~50%) and melting land ice (glaciers and ice sheets, ~50%)
Projections:
- Low emissions: 0.28–0.55 m by 2100
- High emissions: 0.63–1.01 m by 2100 (with higher possibilities if West Antarctic Ice Sheet destabilises)
Impacts:
- Coastal flooding and erosion
- Saltwater intrusion into groundwater and estuaries
- Displacement of coastal communities
- Threat to low-lying nations (e.g. Kiribati, Maldives, Tuvalu)
Measurements:
- Arctic sea ice extent: Satellite passive microwave sensors since 1979
- Antarctic sea ice: Similarly monitored by satellite; different trends from Arctic
- Glacier mass balance: Field measurements + satellite gravimetry (GRACE)
- Snow cover: Satellite remote sensing (MODIS); weather station records
Key findings:
| Indicator | Trend |
|---|---|
| Arctic sea ice extent | Declining ~13% per decade since 1979; summer 2023 all-time record low |
| Antarctic sea ice | More variable; 2023 saw record low winter extent |
| Mountain glacier mass | Losing mass globally; rate accelerating since ~1990 |
| Northern Hemisphere spring snow cover | Declining since the 1970s |
| Permafrost temperature | Increasing across Arctic regions |
Climate system feedbacks:
- Sea ice loss → albedo feedback (more ocean absorbs heat)
- Glacier retreat → affects freshwater supply for billions of people
- Permafrost thaw → releases stored methane and CO$_2$ (positive feedback)
VCAA commonly provides graphs of climate data and asks students to:
1. Describe the trend (direction, rate)
2. Identify periods of unusually rapid change
3. Distinguish between natural variability and long-term trend
4. Evaluate confidence in projections
STUDY HINT: Practise describing trends from graphs precisely. State the direction (increasing/decreasing), the approximate rate (e.g. “~0.2°C per decade”), and note any recent acceleration. Avoid vague statements like “it went up”.
