11.3 Changes in extreme weather events

Climate change is intensifying extreme weather events worldwide. From scorching heat waves to devastating floods, these phenomena are becoming more frequent and severe, posing significant challenges to communities and ecosystems.

Understanding the link between climate change and extreme weather is crucial. While natural variability complicates attribution, observed trends show clear shifts in patterns of heat waves, heavy precipitation, droughts, and other extreme events, with far-reaching impacts on human health, agriculture, and infrastructure.

Extreme Weather Events and Climate Change

Types of climate-influenced extreme weather

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• Heat waves involve prolonged periods of abnormally high temperatures that can lead to heat-related illnesses and deaths (European heat wave in 2003, Russian heat wave in 2010)
• Heavy precipitation events bring intense rainfall or snowfall over a short period causing flooding and damage to infrastructure (Hurricane Harvey in 2017, Kerala floods in India in 2018)
• Droughts are extended periods of below-average precipitation leading to water shortages, crop failures, and increased wildfire risk (California drought from 2011-2017, Cape Town water crisis from 2017-2018)
• Tropical cyclones (hurricanes and typhoons) are intense low-pressure systems with strong winds and heavy rainfall that can cause widespread damage and loss of life
• Wildfires are large, uncontrolled fires in natural areas that can be exacerbated by hot, dry conditions and spread rapidly
• Floods occur when water overflows onto normally dry land, often as a result of heavy precipitation, storm surge, or snowmelt

Challenges in extreme event attribution

• Natural variability in weather and climate patterns fluctuates naturally, making it difficult to distinguish the specific impacts of climate change on individual extreme events
• Limited historical records with short observational data make it challenging to determine long-term trends and separate them from natural variability
• Complex interactions between multiple factors, such as land use changes and natural climate oscillations (El Niño-Southern Oscillation), can influence the occurrence and severity of extreme events
• Modeling limitations exist as climate models have uncertainties in simulating specific extreme events and their regional impacts due to the complex nature of these phenomena

Observed changes in weather extremes

• Heat waves have increased in frequency, intensity, and duration in many regions worldwide, with notable examples like the European heat wave in 2003 and the Russian heat wave in 2010
• Heavy precipitation events have increased in frequency and intensity in some regions, with a shift towards more intense individual storms (Hurricane Harvey in 2017, Kerala floods in India in 2018)
• Droughts have shown varying changes by region, with some areas experiencing more frequent or severe droughts
  • Increased drought risk observed in the Mediterranean region, parts of Africa, and Australia
  • Examples include the California drought from 2011-2017 and the Cape Town water crisis from 2017-2018

Impacts of extreme weather shifts

• Human health impacts include heat-related illnesses and deaths during heat waves, as well as the potential spread of vector-borne diseases (malaria, dengue) due to changing weather patterns
• Agriculture and food security are affected by crop failures and reduced yields due to droughts, floods, or extreme temperatures, leading to increased food prices and potential food shortages
• Infrastructure and property damage occurs during extreme events, with the destruction of buildings, roads, and other critical infrastructure, resulting in increased costs for repair and rebuilding
• Water resources are strained during droughts, while heavy precipitation events and flooding can reduce water quality and damage water infrastructure
• Economic losses result from the disruption of business operations and supply chains, as well as increased insurance costs and potential uninsurability in high-risk areas
• Displacement and migration of communities may be forced due to sea-level rise, coastal flooding, or chronic drought, leading to increased environmental refugees and associated social and political challenges
• Adaptation measures are needed to cope with changing extreme weather patterns, including:
  1. Improved early warning systems and emergency preparedness
  2. Infrastructure upgrades (flood defenses, heat-resistant buildings)
  3. Changes in agricultural practices and water management
  4. Increased public awareness and education on climate change impacts