3 Negative effects of global warming

• 1.
• Melting of ice. A large amount of fresh water is frozen in glaciers and the polar ice masses.
• As the Earth's temperature rises, ice blocks break off and melt.
• Together with the thermal expansion of the warming oceans, this causes sea-level rise and the threat of coastal flooding (a serious danger for low-lying areas such as the Nile Delta, where salt-water intrusion also damages farmland and groundwater), and creates an environmental disaster, including:

• A. Extinction of polar species because of the destruction of their natural habitat (polar bears lose sea ice for hunting; penguins and seals lose breeding grounds), which reduces biodiversity and disturbs the ecological balance.
• B. Severe climate changes: hurricanes, floods, droughts and others. A warmer atmosphere holds more water vapour and has more energy, so extreme weather events become stronger and more frequent; heat waves, wildfires and desertification increase.

Other effects (consistent with the book and your earlier lessons): coral bleaching and loss of reefs (warmer sea water — Module 3 — and acidification — Module 7); changes in rainfall that affect agriculture and water supply (Module 1); shifts in the ranges of animals and plants; spread of diseases; lower dissolved oxygen in warmer water (Module 7); and risks to human health from heat.

• Problem. If 1000 km³ of land ice melts and flows into the oceans (ocean area 3.6 × 10⁸ km²), what is the rise in sea level?
• (Ice density 917 kg/m³, water density 1000 kg/m³.)

Solution. Volume of water = 1000 km³ × 0.917 = 917 km³. Rise = volume/area = 917/3.6 × 10⁸ = 2.55 × 10⁻⁶ km = 2.5 mm. The melting of the whole Greenland ice sheet (about 2.9 million km³ of ice) would raise the sea level by roughly 7 m. (Floating sea ice, such as in the Arctic Ocean, does not raise sea level when it melts, since it already displaces its weight of water, but it reduces the reflectivity of the Arctic and so accelerates warming.)