The broad impacts of global warming on the environment and society

Global warming, driven by climate change, is expected to bring significant and widespread changes to the natural world, human societies, and economic systems. These impacts vary across regions and are subject to uncertainty, as predictions depend on different temperature rise scenarios.

Environmental and societal effects of global warming

• Rising sea levels - Increased temperatures cause ice to melt, leading to higher sea levels that threaten low-lying areas with flooding.
• Intensified storm activity - Warmer conditions are likely to result in more frequent and severe storms, damaging infrastructure and ecosystems.
• Shifting agricultural patterns - Changes in climate may reduce crop yields in some areas, such as the grain belt in the USA, while extending growing seasons in others, like Canada.
• Reduced rainfall in specific regions - Areas such as the USA, southern Europe, and parts of the Commonwealth of Independent States (CIS) may experience less precipitation, affecting water availability.
• Wildlife extinction risk - Up to 35% of species could face extinction due to habitat loss and changing ecosystems.

Changes to the hydrosphere due to climate change

The hydrosphere, encompassing freshwater, seawater, and ice, faces substantial alterations due to global climate change. These changes threaten millions of people and vast areas of land through rising water levels and disrupted water supplies.

Key impacts on the hydrosphere

• Sea level rise and flooding:
  • Melting ice caps and glaciers, combined with the steric effect (water expansion due to warming), are predicted to raise sea levels by 30 to 70 cm by 2100.
  • This increases the risk of flooding in low-lying regions like Bangladesh, potentially displacing up to 190 million people.
• Increased high tides and storm surges:
  • Higher sea levels amplify the impact of tides and storms.
  • This puts cities such as London and New York at greater risk of coastal flooding, necessitating enhanced protective measures like sea walls.
• Threats from melting glaciers:
  • Flooding from glacial melt could affect up to 3.5 million km² of land.
  • This impacts water supply reliability for millions who depend on these sources.

Predicted trends in temperature and sea level rise

• Temperature increase - Average predictions suggest a rise of approximately 2°C by 2100, while a worst-case scenario could see a rise of up to 4.5°C.
• Sea level projections - Corresponding to temperature rises, sea levels are expected to increase by around 0.3 m in average scenarios and up to 0.7 m in worst-case scenarios by the end of the century.

Decline in Arctic sea ice and its consequences

Arctic sea ice has been shrinking significantly since the mid-1970s due to rising global temperatures, with profound effects on the environment and wildlife. This decline is altering weather patterns and ecosystems in the region and beyond.

Patterns of Arctic sea ice decline

• Historical reduction - The extent, volume, and thickness of Arctic sea ice have decreased over decades, with the lowest recorded volume noted in February 2016.
• Extended melting season - The melting period has lengthened by nearly two weeks since 1979, with the annual minimum typically in September and maximum in March.
• Age of ice - Older, thicker ice (over 4 years old) has diminished from over 30% of total ice in 1988 to less than 5% by 2015, indicating a loss of resilient ice cover.
• Future predictions - Scientists forecast that the Arctic could be ice-free during summer months by 2045.

Consequences of shrinking sea ice

• Wave formation feedback loop:
  • Reduced ice cover allows for larger waves, such as 4-metre waves recorded in the Beaufort Sea in 2012.
  • These waves further break up ice, accelerating the decline.
• Weather pattern changes:
  • Loss of sea ice is linked to wetter summers in northern Europe.
  • It also causes extreme weather events in mid-latitude regions of the northern hemisphere.
• Methane emissions:
  • Melting ice may release methane from tundra.
  • This is exacerbated by chlorine atoms from the sea, contributing to further warming.
• Ecosystem impacts:
  • Increased primary productivity leads to plankton blooms.
  • However, reduced ice cover limits polar bear hunting time for seal pups, forcing them onto land with less nutritious diets.
  • This results in smaller body sizes and lower reproductive success.

Retreat of glaciers and ice caps and their impact on water supply

Glaciers and ice caps worldwide are receding due to global warming, with significant implications for water resources, particularly in regions dependent on glacial melt for their supply.

Evidence of glacial retreat

• Himalayan glaciers - Many glaciers in the Himalayas are shrinking, with the Gangotri Glacier retreating over 700 m since 1990.
• European glaciers - The Gorner Glacier in Europe has receded by approximately 2.3 km over the past 120 years, reflecting a long-term trend of ice loss.
• Historical trends - Retreat in some areas, like the Himalayas, has been ongoing since the late 18th century, accelerating in recent decades.

Impacts on water supply and regional stability

• Dependence on glacial water - Over 1.3 billion people rely on rivers originating in the Himalayas for drinking, irrigation, and industrial needs.
• Lowland areas - At lower elevations, glacial retreat may not immediately cause shortages due to monsoon rains, but factors like population growth and groundwater depletion pose future risks.
• Highland concerns - At higher elevations, retreating glaciers could alter stream-flow patterns, affecting water availability and reliability for communities.
• Broader implications - Changes in water supply could lead to regional tensions, as communities and nations compete for diminishing resources in the face of climate-driven scarcity.