Chapter 13 examines climate change in depth. This first lesson establishes what the data shows — where (spatial) and when (temporal) the warming appears. Green boxes are case/place studies; blue are definitions; orange are exam tips. This is a data-reading lesson, so practise interpreting the graphs.
Before the data: where does the science actually stand?
Weather is the day-to-day state of the atmosphere; climate is the long-term average pattern (typically 30+ years). Climate change is a shift in those long-term patterns.
Among climate scientists there is overwhelming agreement that Earth is warming and that human activity is the main cause. The scientific debate about whether and why is effectively settled — the remaining questions are about pace, impacts and responses. (Public and political debate is a separate thing from the scientific consensus.)
Natural variation is expected, but the current changes are inconsistent with natural cycles and coincide precisely with industrialisation and fossil-fuel use — the human fingerprint established in 12.1.
Don't confuse the (settled) scientific consensus with (ongoing) political debate. Examiners value a student who distinguishes evidence from opinion.
How the warming has unfolded over time — the “temporal” characteristic.
NASA and other agencies show Earth's global average temperature has risen by roughly 1.1–1.2 °C since the late nineteenth century, with the fastest warming in the last three to four decades. Almost all of the warmest years on record have occurred this century.
The fact that multiple independent datasets agree (NASA GISTEMP, NOAA, the UK's HadCRUT, Berkeley Earth, Europe's ECMWF) is itself strong evidence — the trend is not an artefact of one method.
The oceans absorb most of the extra heat — with consequences for storms.
The temperature of the very top layer (about the top millimetre) of the ocean — a key climate indicator tracked back to the 1880s.
The ocean has absorbed the great majority of the extra heat trapped by greenhouse gases, so SSTs have risen steadily since the late 1800s. Because warm water is the fuel for tropical storms, warmer oceans mean more energy for hurricanes, cyclones and typhoons — a driver of more intense storms.
Warming is global but uneven — the “spatial” characteristic.
Temperature-anomaly maps show that nearly every region has warmed — very few areas are cooler than their historical average. But the warming is uneven: the Arctic has warmed fastest (Arctic amplification, from 12.1), while some ocean regions lag.
The local, verifiable evidence — the examiner's favourite.
The Bureau of Meteorology has kept reliable records since 1910. The data show:
Extreme heat events and dangerous fire-weather days have increased across much of Australia — a direct human-system consequence that connects to Chapter 14 (Bushfires).
Verified Australian evidence of both temporal (warming trend) and spatial (whole-continent) characteristics. Concepts: environment, change, place, scale.
PlaceChangeScale“2019 the warmest year” was correct when the source was written; newer years may have equalled or exceeded it. Always quote the BoM/CSIRO report and year, and check for the latest data before an exam.
Check you can do these before moving to 13.2 (Causes).
13.1 established what the data shows. Next, 13.2 Causes separates the natural from the human causes of that change; then 13.3 Impacts and 13.4 Responses (with Costa Rica).
Everything in this chapter traces to a source you can check. Watch the explainer, read the primary sources, follow the news, and practise the geographical skills this chapter uses.