The impacts of climate change
AdvancedAbout 1.2 degrees of warming has already shrunk glaciers, lifted seas about 20 cm over a century, supercharged heatwaves, downpours and typhoons, bleached corals and shifted species. Hong Kong faces more hot nights, fiercer rainstorms, flooding in low areas such as Tai O, and warming seas.
- About 1.2 degrees of average warming multiplies extremes: heatwaves, downpours, fierce typhoons
- Ice: Greenland and Antarctica shedding fast; the Asian water tower shrinking
- Sea: about 20 cm in a century, 3.7 mm a year now; acidification rising
文體小知識：影響評估課：把影響分「全球與香港」兩層、「環境與社會經濟」兩類，用升溫約1.2攝氏度換來的具體變化作證據。
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1A rise of about 1.2 degrees sounds small, but small shifts in the average become extremes in reality. First, the cryosphere: the Greenland and Antarctic ice sheets are losing mass faster and mountain glaciers retreat worldwide; the Himalayan glaciers — the 'water tower of Asia' feeding great rivers — may lose most of their volume by 2100, threatening water for hundreds of millions downstream.
2Second, the oceans: warming water expands, and meltwater adds more, raising global sea level about 20 cm in the twentieth century and now about 3.7 mm a year and accelerating; the sea also acidifies as it absorbs CO2. Third, extreme weather: heatwaves come hotter and longer — 2023 was the hottest year on record; warmer air holds more moisture, so downpours hit harder; warmer oceans feed typhoons more energy, strengthening both wind and rain.
3Ecosystems strain on all fronts: warmer, more acidic seas bleach corals — Australia's Great Barrier Reef has suffered repeated mass bleaching; species march poleward and uphill, and those that cannot keep pace face extinction; shrinking Arctic sea ice starves polar bears of hunting grounds. Harvests swing, and the ranges of dengue and malaria mosquitoes widen — society suffers too.
4Hong Kong feels it directly: very hot nights keep climbing, denying sleep and raising heat-stroke risk for the elderly; the Observatory has measured a long-term rise in Victoria Harbour sea level; the September 2023 rainstorm set an hourly rainfall record and flooded low-lying Tai O; and super typhoon Mangkhut in 2018 felled countless trees and broke records. Climate change is not a faraway polar-bear story — it is already written into Hong Kong's daily weather report.
1Summary 重點摘要
About 1.2 degrees of warming has already shrunk glaciers, lifted seas about 20 cm over a century, supercharged heatwaves, downpours and typhoons, bleached corals and shifted species. Hong Kong faces more hot nights, fiercer rainstorms, flooding in low areas such as Tai O, and warming seas.
2Vocabulary cards Vocabulary
The vast ice of Greenland and Antarctica; its loss is a main driver of sea-level rise.
The steady shrinkage of glaciers, seen worldwide in mountain ranges.
Rising seas from thermal expansion and meltwater — about 20 cm globally in the twentieth century.
The sea turning acidic as it absorbs CO2, hindering shells and corals.
Overheated seas make corals expel their algae and turn white; prolonged heat kills — as on the Great Barrier Reef.
Heatwaves, downpours and fierce typhoons growing more frequent and intense as the world warms.
A night staying at 28 degrees Celsius or above; Hong Kong's hot nights keep rising, endangering the elderly.
Warmer air holds more moisture, so downpours intensify — Hong Kong's September 2023 black rainstorm broke hourly records.
The Himalayan glaciers feeding Asia's great rivers; warming melts the store away.
The 2018 super typhoon that set wind records in Hong Kong, felling tens of thousands of trees and flooding low areas.
3Step by step Steps
- Para 1: the cryosphere melts fasterThe cryosphere is where climate change shows first. The Greenland and Antarctic ice sheets shed ice in the hundreds of billions of tonnes each year, and mountain glaciers retreat worldwide, sending meltwater into the sea. The Himalayas, the 'water tower of Asia', feed over a billion people across the Yangtze, Ganges and Indus basins; studies suggest the region could lose most of its ice by 2100, putting huge strain on downstream farms and cities.
- Para 2: rising seasWarmer water expands, and meltwater keeps pouring in, so seas rose about 20 cm over the twentieth century and are now climbing about 3.7 mm a year and accelerating. Another metre would threaten hundreds of millions of coastal residents; low-lying island nations such as Tuvalu risk being swallowed altogether, while delta cities pay enormous sums for flood defence.
- Para 2: extreme weather multipliesA warmer average makes extremes more frequent and fiercer. 2023 was the hottest year on record; Europe's 2022 heatwave killed more than 60,000 people; in September 2023 Hong Kong recorded 158.1 mm of rain in a single hour, breaking the record and flooding wide areas; and Mangkhut broke wind records over Hong Kong in 2018. A small shift in the mean, a multiplication of extremes — that is climate change in one line.
- Para 3: ecosystems under strainEcosystems are finely tuned to temperature. Warmer seas have bleached the Great Barrier Reef again and again, and when corals die in great patches the whole food web that depends on them suffers; mountain species climb about 10 metres a decade in search of cooler air; shrinking Arctic sea ice strips polar bears of hunting grounds and breeding platforms. Species that cannot keep pace with the changing climate face endangerment or extinction.
- Para 4: Hong Kong's impactsFor Hong Kong, climate change is not a distant issue but a reality already here. Observatory records show ever more very hot nights, long-term sea-level rise in Victoria Harbour, and repeated flooding in low-lying Tai O during storms; when Mangkhut struck in 2018, tens of thousands of trees fell and some districts took more than a week to restore transport and power. Flood defences, urban planning and the resilience of vulnerable groups all need reviewing for the new normal.
- Answer framework: from global to Hong KongStructure impact answers in layers: first the global picture — melting ice, rising seas, extreme weather and ecosystem strain; then Hong Kong's hot nights, rainstorms, flooding and typhoon damage; finally the knock-on effects on food, health and the economy. Support every point with a year or figure, and open with a line such as 'small average shifts, huge extremes' to show you grasp the whole pattern.
4Diagrams Diagrams
5Worked example Example
Example: the global average has risen only about 1.2 degrees — why are the impacts so huge? Explain through glaciers, sea level and extreme weather.
- Small average shifts mean big extremes: one degree of average warming multiplies heatwave and hot-night days — Hong Kong's hot nights have climbed from single digits to dozens a year
- Glaciers: warming melts ice sheets and glaciers fast — Greenland sheds hundreds of billions of tonnes a year, and the Asian water tower shrinks, threatening great rivers
- Sea level: expansion plus meltwater lifted seas about 20 cm in a century and still accelerating; low islands and delta cities are hit first
- Extremes: warmer air carries more moisture for fiercer rain (158.1 mm in an hour, September 2023), and warmer oceans feed stronger typhoons (Mangkhut)
- Answer: Because 1.2 degrees is a global average: applied to real systems it magnifies into collapsing glaciers, accelerating seas and frequent extremes — a small rise in the mean, a multiplication of extremes. Tip: open impact answers with 'average to extreme' and support each item with dated figures.
6Common mistakes Mistakes
7Quick check Quick check
Q1What are the two main causes of sea-level rise?
Q2How much did global sea level rise in the twentieth century?
Q3What is the 'water tower of Asia', and how does warming threaten it?
Q4What causes coral bleaching?
Q5Give two examples of Hong Kong feeling climate change.
8Recap Recap
- About 1.2 degrees of average warming multiplies extremes: heatwaves, downpours, fierce typhoons
- Ice: Greenland and Antarctica shedding fast; the Asian water tower shrinking
- Sea: about 20 cm in a century, 3.7 mm a year now; acidification rising
- Ecology: coral bleaching, species on the move, polar bears losing hunting grounds
- Hong Kong: more hot nights, record rainstorms, Tai O floods, Mangkhut-style typhoons