Impacts: Extreme Weather

1. Impacts: Extreme Weather 69EG3137 – Impacts & Models of Climate Change Details for Today: DATE: 14th April 2005 BY: Mark Cresswell FOLLOWED BY: NOTHING

2. Topics • A Definition of Extreme Weather • Storm events • Fires • Floods and Drought • Oceans • Effects on ENSO • Societal Impacts • Summary

3. A Definition • Extreme weather may be regarded as an anomalously high magnitude weather event leading to deleterious effects upon natural or human systems • Extreme weather events are a potential response to climate change • These events, when they occur over land, will often lead to damage to crops and buildings or loss of life and economic hardship

4. Storm Events • Of all the extreme weather events – storm events cause greatest loss of life and damage to property • Hurricanes – centres of intense low pressure that feed of heat and moisture over warm seas and land • Tropical cyclones – primarily the result of above normal SSTs • Intense hailstorms and associated high winds and rainfall

5. Storm Events

6. Storm Events

7. Storm Events • Magnitude and frequency of large-scale storms largely depends on SST anomalies • Purely continental storm systems rely upon intense surface heating from solar energy – a process enhanced by deforestation and subsequent changes to surface albedo

8. Fires • During periods of prolonged drought natural vegetation will begin to die back and dry • Environments of this type will be highly susceptible to either accidental or naturally occurring fire events • Some ecosystems rely upon fire events to allow seeds to germinate and release nutrients into the soil • Climate change may enhance both the magnitude and frequency of fire events

9. Fires

10. Floods and Drought • Floods may be caused by excessive rainfall or changes to the natural hydrology leading to saturation of soils • Apart from damage to property, crops and loss of life, flood events may damage the landscape – making it more vulnerable to wind erosion • Floods will become more common in areas where climate change generates enhanced precipitation

11. Floods and Drought • Drought is caused both by diminished precipitation due to climate change or human activities • Droughts can make environments more vulnerable – affecting wind erosion, soil moisture, crop/food security and human health • Prolonged droughts may lead to a higher incidence of fires

12. Floods and Drought

13. Floods and Drought

14. Floods and Drought

15. Oceans • One particular concern with climate change is the effects on ocean surface water temperatures • Apart from the boundary forcing an SST has on atmospheric characteristics, the biological effects can be significant • Algal blooms can form off warm water coasts – depleting the waters of oxygen • Changes to nutrient supply can affect fish stocks (esp. in El Niño years)

16. Oceans

17. Effects on ENSO • Climate simulations performed with AGCMs using prescribed background SSTs and ENSO-like SST anomalies indicate: • No change in the frequency of El Niños • Greater differences in precipitation and soil moisture between El Niño and La Niña years • Very different patterns of change in sea-level and upper tropospheric pressure outside the tropics in response to El Niños – compared to the changes that occur under present conditions Harvey, 2000

18. Effects on ENSO • Wet and dry extremes will tend to be intensified as climate warms because: • Non-linearity of the Clausius-Clapeyron equation which governs the relationship between the temperature of a liquid and its vapor pressure

19. Effects on ENSO • Wet and dry extremes will tend to be intensified as climate warms because: 2) A given change in SST will have a larger effect on evaporation the warmer the base climate 3) Enhanced evaporation over the eastern Pacific when an El Niño occurs in a warmer climate will lead to a greater increase in precipitation in this region, greater rising motion and greater compensating subsidence in the western Pacific 4) Similar changes, but with the opposite geographical pattern shown in (3) will occur in La Niña events

20. Societal Impacts From: IPCC 2001 – Impacts, adaptation and vulnerability HIGH • Established but incomplete • Increased vulnerability of infrastructure to urban flooding and landslides • Tropical cyclones more destructive • Fire danger to urban/rural fringe increased • Sea-level rise increases cost/vulnerability • Water supplies more vulnerable • Well-Established • Sea-level rise increases cost/vulnerability of coastal infrastructure • Energy demand sensitive; parts of energy supply vulnerable • Local capacity critical to successful adaptation • Infrastructure in permafrost regions vulnerable Level of agreement/consensus • Competing Explanations • Agroindustry and fisheries vulnerable • Heat-waves more serious for human health • Heat island effects increase summer energy demand and reduce winter energy demand • Increased air and water quality problems • Speculative • Fire damage to key resources increased • More hail and windstorm damage HIGH LOW Amount of evidence (observations, model output and theory)

21. Summary • Extreme weather events are likely to become more serious under a warmer climate • Impacts on natural ecosystems with be great – with events such as fires, floods, drought and algal blooms • Impacts on human society will induce greater hardship, loss of life and economic losses • READ THE IPCC REPORTS!!