17.2 Impacts of Climate Change on Physical Systems

Climate change is messing with our planet big time. It's heating things up, changing rain patterns, and causing more extreme weather. These changes are hitting our oceans, land, and air hard, affecting everything from tiny plankton to entire ecosystems.

The impacts are far-reaching and complex. Rising seas threaten coastal areas, while warmer, more acidic oceans harm marine life. On land, species are shifting habitats and struggling to adapt. It's a wake-up call for how our actions are reshaping Earth's systems.

Climate change effects on temperature and precipitation

Global temperature increase

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• The Earth's average global temperature has increased by approximately 1.1°C since pre-industrial times, primarily due to anthropogenic greenhouse gas emissions
• Climate models project that global average temperatures will continue to rise by 1.5°C to 4°C by the end of the 21st century, depending on future greenhouse gas emission scenarios
  • The Paris Agreement aims to limit global warming to well below 2°C, preferably to 1.5°C, compared to pre-industrial levels
  • Achieving the 1.5°C target would require rapid and far-reaching transitions in energy, land use, transportation, and industrial systems
• Warming is not uniform across the globe, with polar regions experiencing more rapid temperature increases than the global average, a phenomenon known as polar amplification
  • The Arctic is warming at a rate two to three times faster than the global average
  • Polar amplification is caused by positive feedback loops, such as the ice-albedo feedback, where melting ice reveals darker surfaces that absorb more solar radiation

Changes in precipitation patterns

• Climate change is altering global precipitation patterns, leading to increased precipitation in some regions and decreased precipitation in others
  • Warmer temperatures increase evaporation rates, leading to more water vapor in the atmosphere and potentially more intense precipitation events
  • Shifts in atmospheric circulation patterns, such as the expansion of the Hadley cell, can lead to changes in the location and intensity of precipitation
• Changes in temperature and precipitation patterns can lead to more frequent and severe droughts in some regions, while other areas may experience increased flooding risk
  • Regions such as the Mediterranean, southern Africa, and parts of South America are projected to experience increased drought risk
  • Regions such as the mid-latitudes and the tropics are expected to experience increased heavy precipitation events and flooding risk
• Changes in precipitation patterns can have significant impacts on agriculture, water resources, and ecosystem functioning
  • Crop yields may decline in regions experiencing increased drought stress, while excessive rainfall can lead to soil erosion and nutrient leaching
  • Changes in the timing and availability of water resources can affect human settlements, energy production, and biodiversity

Climate change impacts on oceans

Sea level rise

• Global sea levels are rising due to two primary factors related to climate change: thermal expansion of ocean water and the melting of land-based ice sheets and glaciers
  • Thermal expansion occurs as ocean water warms and expands, accounting for approximately one-third of observed sea level rise
  • Melting of land-based ice, particularly from the Greenland and Antarctic ice sheets, contributes significantly to sea level rise
• Sea level rise threatens coastal communities and infrastructure, increases the risk of flooding and erosion, and can lead to the displacement of millions of people
  • Low-lying coastal areas, such as small island states and densely populated river deltas, are particularly vulnerable to sea level rise
  • Coastal flooding and saltwater intrusion can impact freshwater resources, agricultural land, and human settlements
• Projections of future sea level rise vary depending on the rate of greenhouse gas emissions and the response of ice sheets
  • Under a high-emissions scenario, global sea levels could rise by 0.6 to 1.1 meters by 2100
  • Long-term sea level rise over the next several centuries to millennia could be even more substantial, potentially reaching several meters

Ocean acidification

• Ocean acidification is the process by which the ocean's pH decreases as it absorbs excess atmospheric carbon dioxide (CO2)
  • As atmospheric CO2 concentrations increase due to anthropogenic emissions, the ocean absorbs more CO2, leading to the formation of carbonic acid and lowering the ocean's pH
  • The average pH of the ocean surface has decreased by approximately 0.1 units since pre-industrial times, representing a 30% increase in acidity
• Ocean acidification can have detrimental effects on marine organisms, particularly those with calcium carbonate shells or skeletons, such as corals, mollusks, and some plankton species
  • Lower pH can impair the ability of these organisms to build and maintain their shells or skeletons, affecting their growth, reproduction, and survival
  • Changes in the abundance and distribution of these organisms can have cascading effects on marine food webs and ecosystems
• Ocean acidification can also affect the behavior, sensory abilities, and metabolism of marine organisms
  • Some fish species have shown impaired sensory functions and altered behavior in acidified conditions, potentially affecting their survival and ecological interactions
• The impacts of ocean acidification are expected to intensify as atmospheric CO2 concentrations continue to rise
  • Limiting global warming and reducing greenhouse gas emissions is crucial for mitigating the progression of ocean acidification

Climate change and extreme weather

Heatwaves and droughts

• Climate change is increasing the frequency, intensity, and duration of various extreme weather events, such as heatwaves, droughts, heavy precipitation events, and tropical cyclones
• Heatwaves are becoming more frequent and intense due to rising global temperatures
  • Warmer baseline temperatures increase the likelihood of extreme heat events, as smaller temperature deviations can push conditions into record-breaking territory
  • More frequent and intense heatwaves can lead to increased heat-related illnesses and fatalities, particularly among vulnerable populations (elderly, children, outdoor workers)
• Droughts are expected to become more frequent and severe in many regions as a result of changes in precipitation patterns and increased evaporation due to higher temperatures
  • Regions such as the Mediterranean, southern Africa, and parts of Australia are projected to experience increased drought risk
  • More frequent and severe droughts can lead to water scarcity, reduced agricultural productivity, and increased wildfire risk

Heavy precipitation and tropical cyclones

• Heavy precipitation events are becoming more common and intense in some areas, as warmer air can hold more moisture, leading to increased water vapor in the atmosphere
  • The frequency of heavy precipitation events has increased in many regions, particularly in the mid-latitudes
  • More intense precipitation events can lead to increased flooding risk, soil erosion, and damage to infrastructure
• Tropical cyclones (hurricanes and typhoons) are likely to become more intense, with higher wind speeds and more heavy precipitation, as a result of warmer ocean surface temperatures
  • Warmer ocean surface temperatures provide more energy for tropical cyclone formation and intensification
  • While the overall frequency of tropical cyclones may not increase, the proportion of high-intensity storms (Category 4 and 5) is expected to rise
• The impacts of extreme weather events are not evenly distributed, with developing countries and vulnerable communities often facing disproportionate risks
  • Enhancing resilience and adaptive capacity, particularly in vulnerable regions, is crucial for reducing the impacts of extreme weather events
  • Investing in early warning systems, disaster risk reduction, and climate-resilient infrastructure can help mitigate the consequences of extreme weather events

Climate change consequences for ecosystems

Species range shifts and phenological changes

• Climate change is altering the distribution, composition, and functioning of ecosystems worldwide, leading to significant impacts on biodiversity
• Species are responding to changing climatic conditions by shifting their geographic ranges, often moving towards the poles or to higher elevations in search of suitable habitats
  • Range shifts can lead to the decoupling of species interactions, such as predator-prey relationships or plant-pollinator interactions, affecting ecosystem stability
  • Some species may be unable to keep pace with the rate of climate change or may face barriers to dispersal, increasing their risk of extinction
• Changes in the timing of seasonal events, known as phenological shifts, are occurring in response to climate change
  • Warmer temperatures can lead to earlier spring events, such as leaf emergence, flowering, and animal migration
  • Mismatches in the timing of interrelated species' life cycles can disrupt ecological interactions and food webs

Ecosystem stressors and regime shifts

• Climate change is exacerbating other stressors on ecosystems, such as habitat fragmentation, overexploitation, and invasive species, leading to compound effects on biodiversity
  • The combined impacts of climate change and other anthropogenic pressures can accelerate biodiversity loss and ecosystem degradation
  • Protecting and restoring ecosystems, reducing non-climatic stressors, and promoting ecological connectivity can enhance ecosystem resilience to climate change
• Coral reefs, which are highly sensitive to changes in ocean temperature and acidity, are experiencing widespread bleaching events and mass die-offs due to climate change
  • Coral bleaching occurs when stressed corals expel their symbiotic algae, leading to the loss of their primary food source and often resulting in coral mortality
  • The loss of coral reefs has devastating consequences for the diverse marine species that depend on them for habitat and food, as well as for the human communities that rely on reefs for coastal protection, tourism, and fisheries
• Climate change is increasing the risk of ecosystem regime shifts, where an ecosystem rapidly transitions from one stable state to another, often with significant consequences for biodiversity and ecosystem services
  • Examples of potential regime shifts include the conversion of Amazon rainforest to savanna, the collapse of Arctic sea ice, and the bleaching and mortality of coral reefs
• Mitigating greenhouse gas emissions, protecting biodiversity, and promoting ecosystem-based adaptation strategies are essential for reducing the risks of climate change to ecosystems and the services they provide