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Sea-level rise occurs primarily due to two mechanisms: the thermal expansion of seawater as it warms and the melting of terrestrial ice, which increases the volume of ocean water. The Greenland and Antarctic ice sheets—both situated on land—are experiencing accelerated thinning, compounding the effects of thermal expansion. Although the precise magnitude of future sea-level rise remains uncertain, advances in climate modelling have improved predictive accuracy. According to the Intergovernmental Panel on Climate Change (IPCC), a global temperature increase of 1.5°C to 4.5°C could result in sea-level rises between 15 and 95 cm. These estimates assume a proportional relationship; however, surpassing climatic tipping points could lead to rises of several metres. Approximately 40 nations are expected to be severely affected, with low-lying states such as Bangladesh, the Maldives, and the Netherlands losing substantial land area, and some—like Tuvalu—potentially disappearing entirely.

Oceans act as major carbon sinks, absorbing nearly half of anthropogenic carbon dioxide emissions. Consequently, ocean acidity has increased by approximately 25% since pre-industrial times. This acidification adversely affects marine organisms, particularly corals, and diminishes the ocean’s capacity to absorb further CO₂ as it warms.

Melting land ice in Greenland and Antarctica contributes directly to sea-level rise as meltwater flows into the oceans. In contrast, the melting of floating Arctic sea ice does not increase ocean volume due to water displacement equilibrium. Nevertheless, glacial melt contributes additional volume. The potential complete melting of the Greenland ice sheet could disrupt the North Atlantic Drift (NAC) by diluting ocean salinity. A slowdown or cessation of the NAC and Gulf Stream could result in significantly colder climates in the United Kingdom and Scandinavia. Conversely, Arctic ice melt may open new trade routes, facilitate navigation, and enable resource exploitation of undersea minerals and fossil fuels. However, the destabilization of methane clathrates—ice formations trapping methane beneath the Arctic Ocean floor—poses a severe risk of accelerating global warming through methane release.

Since the end of the Little Ice Age (approximately 1550–1850), most glaciers have retreated, with temporary stabilization between 1950 and 1980 due to global dimming caused by air pollution. Glacial retreat leads to flooding, landslides, and the reduction of freshwater supplies for downstream populations. Major Asian rivers such as the Ganges, Brahmaputra, Indus, Yellow, and Yangtze depend on Himalayan glacial melt. Rapid ice loss has also caused drought conditions, notably in Tanzania, where Mount Kilimanjaro has lost over 80% of its glacier volume.

As atmospheric heat content increases, so does climatic energy, resulting in more extreme and unpredictable weather events. Global precipitation may increase by up to 15%, heightening risks of soil erosion, drought, and salinization from irrigation. Evidence indicates that severe storms, cyclones, and droughts are becoming more frequent and intense. Notable examples include Hurricane Ian in Florida (2022), Storm Filomena in Madrid (2021), and prolonged droughts in the Horn of Africa. ENSO (El Niño–Southern Oscillation) events have also become more extreme and persistent.

Warmer temperatures accelerate biochemical processes such as photosynthesis and respiration. While longer growing seasons in Europe may initially enhance yields, increased respiration and water stress can offset these gains. Biome shifts northward could benefit some regions but harm others, depending on soil fertility. For instance, migration of agriculture from Ukraine’s fertile black soils to Siberia’s less fertile terrain could reduce global productivity. Predictions for changes in net primary productivity (NPP) range from –70% to +11%, reflecting high uncertainty. Warmer conditions also expand the ranges of crop pests.

Desertification, the degradation of land into non-productive desert, now threatens approximately 41% of Earth’s land surface, home to two billion people. Affected regions include the Sahel, the Gobi Desert, Mongolian grasslands, and drylands in East Africa and South America.

Wildfires, intensified by droughts, devastate ecosystems, as seen in Australia’s 2019–2020 bushfires, which affected an estimated 143 million native mammals. In Indonesia, peatland fires have burned for years, releasing vast amounts of carbon. Additionally, insect outbreaks such as pine beetle infestations in British Columbia have worsened under milder winters. Coral reefs are particularly sensitive; a mere 1°C temperature rise can cause bleaching by expelling symbiotic algae, ultimately leading to ecosystem collapse.

Climate change poses serious health challenges. Heatwaves, such as those in Europe (2006), have caused thousands of deaths. Vector-borne diseases like malaria, dengue, and yellow fever are spreading to higher latitudes. Warmer waters promote algal blooms, some of which are toxic, while wetter climates increase fungal infections and drier ones exacerbate respiratory illnesses. Conversely, milder winters could reduce cold-related mortality and heating costs.

Rising evaporation rates may cause rivers and lakes to dry up, forcing populations to migrate. Approximately 2.4 billion people depend on Himalayan-fed river systems, where glacier retreat threatens water security. Similar trends are evident in Europe and North America. Disputes over water—often referred to as “water wars”—are increasingly common.

Declining food and water availability is expected to trigger large-scale human migration. The IPCC estimates that by 2050, climate change could displace up to 150 million people, creating significant geopolitical, economic, and humanitarian challenges.

Indigenous and pastoral communities, such as the Mbororo of the Sahel, possess traditional ecological knowledge that enables adaptive management of fragile ecosystems. However, population pressures and intensifying droughts are undermining traditional practices like transhumance, threatening cultural and economic survival.

Climate change is not solely an environmental crisis but also a profound social one. According to the World Bank, the poorest populations—those least responsible for greenhouse gas emissions—bear the greatest burdens. Addressing climate justice requires tackling inequalities both between and within nations, as well as intergenerational disparities.

National economies will experience divergent impacts. Regions suffering from droughts, floods, or cyclones will incur economic losses, while others may benefit from new resource opportunities in thawing permafrost or navigable Arctic routes, such as the Northwest Passage—first navigable in 2007.