What Is Global Warming?
Global warming refers to the observed increase in Earth's average surface temperature over the last 150 years, primarily due to human activities that release greenhouse gases into the atmosphere.
Since the pre-industrial period (~1850), the global average temperature has risen by approximately 1.2°C. This may sound small, but even this change is causing significant effects worldwide.
Evidence for Global Warming
- Temperature records: data from thousands of weather stations and ocean buoys show a steady warming trend
- Shrinking glaciers: glaciers on every continent are retreating (some have completely disappeared)
- Melting Arctic sea ice: summer Arctic ice extent has fallen by ~40% since the late 1970s
- Rising sea levels: seas have risen ~20 cm since 1900 (thermal expansion of water + melting ice)
- Changes in plant and animal behaviour: earlier flowering dates, species shifting their ranges poleward or to higher altitudes
The Intergovernmental Panel on Climate Change (IPCC) is a scientific body that reviews thousands of peer-reviewed studies. Its reports state that it is "unequivocal" that human influence has warmed the climate since the pre-industrial period.
Consequences of Global Warming
Physical impacts:
- More frequent and intense heatwaves
- Melting ice sheets (Greenland, Antarctica) contributing to sea-level rise
- Ocean warming and acidification — damaging coral reefs
- Disruption of rainfall patterns — some areas get wetter, others drier
Human impacts:
- Flooding of low-lying coasts and islands (Pacific island nations are at severe risk)
- Reduced agricultural yields in tropical regions
- Increased risk of wildfires (e.g. Australia 2019-20, California annually)
- Displacement of populations and increased conflict over water resources
What We Can Do
Slowing global warming requires reducing greenhouse gas emissions:
- Switching from fossil fuels to renewable energy (wind, solar, hydroelectric)
- Improving energy efficiency in buildings, transport, and industry
- Protecting forests — they absorb CO₂
- Carbon capture and storage technologies
Under the 2015 Paris Agreement, nearly 200 countries agreed to limit global warming to well below 2°C (ideally 1.5°C) above pre-industrial levels. Meeting this target requires achieving net-zero carbon emissions by around 2050.
Real world: Australian bushfires 2019–20 and climate change
The 2019–20 Australian Black Summer bushfires burned over 18.6 million hectares — an area larger than the UK. The fires killed or displaced nearly 3 billion animals and destroyed over 3,000 homes. Climate scientists linked the fires directly to global warming: Australia experienced its hottest and driest year on record in 2019, creating tinder-dry conditions. Smoke clouds circled the globe, and air quality in Sydney reached 11 times the hazardous level. Insurance losses exceeded AUD 2.3 billion.
Real world: Coral bleaching on the Great Barrier Reef
The Great Barrier Reef — the world's largest coral reef system, stretching 2,300 km along Australia's northeast coast — has experienced five mass bleaching events since 1998, with the worst in 2022 affecting 91% of surveyed reefs. Bleaching occurs when ocean temperatures rise just 1–2°C above average, causing corals to expel their symbiotic algae and turn white. Without the algae, corals starve and die. The reef generates AUD 6.4 billion annually in tourism and supports over 64,000 jobs — all threatened by continued warming.
Real world: Tuvalu — a nation threatened by sea-level rise
Tuvalu, a Pacific island nation of 11,000 people, has an average elevation of just 2 metres above sea level. Rising seas — driven by global warming — are already flooding low-lying areas during high tides. Salt water is contaminating freshwater supplies and killing crops. In 2022, Tuvalu signed a deal with Australia to allow all its citizens to migrate there as climate refugees — the first agreement of its kind, acknowledging that an entire nation may become uninhabitable due to climate change.
Where do you see this in real life? Track the record-breaking temperature years in the news — the hottest year on record has been broken repeatedly in recent decades. Global average temperature data (NASA, NOAA) are publicly available, showing the warming trend clearly. The 20 hottest years on record have all occurred since 1995.