Extreme Events Flashcards
What is an Extreme Event
When the environmental conditions of an area rank above or below a threshold value, based on historical measurments
(Temperatures, Precipitation, Drought, Ice Storms, Wind Storms)
How do Extreme events link to anthropogenic climate change
Increased extreme event occurrence and severity can be linked to anthropogenic climate change
Over the last 5 decades, average global temperatures have risen sharply to be approximately 0.7 degrees higher than 1961-1990 baseline average
This is down to the greenhouse effect, which has been amplified due to
Mass production and Consumption
Population expansion
What oceanic process can rising temperatures effect
Altantic Meridonial Oceanic Circulation (AMOC)
Rising temperatures are also causing ice sheet to shrink
What secondary impacts does this have
Positive feedback effect due to reduced albedo of the earth
Meaning less heat is being reflected from the earths surface
Sea level rise is caused primarily by two factors related to global warming
Name them
1) Added water from melting ice sheets and glaciers
2) Expansion of seawaer as it warms
What % of extreme weather events studied are more likely or more severe because of anthropogenic climate change
> 70%
(rainfall flooding and drought being most effected)
In what ways are urban populations effected by heatwaves
- Health - heat stress particularly for elderly and young
- Infrastructure pressure - melting/buckling of engineering works, overheating of components
- Energy demand - increased demand for AC and refrigeration
Overall impact the running of the city
In 2022 in the UK 40 degrees was recorded for the first time in the UK and in 2023 a record high of 52.2 degrees was recorded in China
What is the significance of these events
These extreme events are occuring sooner than what was predicted by scientists
What is a heat dome
- the result of a strong change in ocean temperature
- Creates low pressure area with rising warm air moving into and above the land
- As it move it get trapped by the jet stream that is approaching the land
- The hot air is pushed down towards the land and cannot rise to escape
Why is the heat dome a positive feedback system
When the hot air gets trapped by the jet stream, it causes pressure increases
This results in more heat being released
Until the jet stream movs the heat remains
Name a secondary impact of Heatwaves
Wildfires
Wildfire intensity and severity is increasing as a result of dryer conditions and higher winds
Drought (prolongd dry periods in a natural climate cycle)
Rising temperatures caused by climate change means water evaporates even more quickly and enhances the effect of drought
How can flooding be effected by heatwaves
Flooding often occurs after periods of dry weather due to compacted land, which causes more water runoff
There are 4 types of flooding
Describe Costal flooding
- Costal flooding occurs during and after storm events and is exacerbated by rising sea levels and costal erosion
- Water will overwhelm coastal defenese
Describe River Flooding (Fluvial)
- Occurs most frequently as a result of extreme precipitation that overwhelms river channels and flood defences
- Water moves into the natural flood plain when overwhelmed
Describe Groundwater Flooding
results from the water table rising above the surface usually because of a prolonged wet period
(low lying areas are particularly vulnerable)
What is surface water (pluvial) flooding
- occurs when the volume of rainfall exceeds drains and surface water sewers and cannot drain away through drainage systems or soak away
- Urban areas are particularly prone due to lacking porous land to assist with drainage
The UK State of Climate Report has shown that the UK is becoming…
…Wetter
(UK is predicted to become wetter in the winter but hotter and drier in the summer - more extreme)
Which type of flooding is the largest cause of property damage in the UK
(3.8 million properties are at risk)
Pluvial
(suggests current flood defences are probably not sufficient)
Why is Urban Pluvial Flooding so bad?
- Historically, humans built settlements by rivers for freshwater supply and coastal areas to facilitate trade links
Results in us living in a pathway for flooding - Lack of permeable surfaces leads to run-off
- Old and insufficient infrastructure
What are Sustainable Urban Drainage (SuDs)
- SuDs are drainage solutions that provide an alternative water pathway to direct channelling of surface water through networks of pipes and sewers into nearby aquatic environments (minimics natural drainage regimes)
- Essentially making urban environments more permebable
In what two ways can SuDs help?
- Lowering flow rates to watercourses
- Increasing water storage capacity (storing or re-using surface water at source)
This can also improve water quality and biodiversity
Name some types of SuDs
- Inflitration Basins
- Swales
- Filter strips
- Detention ponds
- Soakaways
- Green roofs
- Infiltration trenches
- Biorretention areas
- Wetlands
- Pervious pavements
What is a Combined Sewer Overflow (CSOs)
In the UK we have a combined sewage system which put rainwater and waste water (i.e. toilet waste) into the same pipe
What are Combined Storm Overflows (CSO)
Storm overflows act as relief valves to stop these systmes becoming overwhelmed allowing water companies to discharge dilute raw sewage into England’s river and coastal water
However should only be used in ‘exceptional circumstances
What is the Issue with Combined Sewer Overflow how?
Legally allowed to discharge sewage into rivers ‘under extreme circumstances’ - only no one ever properly defined what these extreme circumstances were
2022- raw sewage was pumped into rivers 824 times per day and extreme precipitation events resulting from climat change will exacerbate this problem
Define a Monsoon
A seasonal change in the direction of the prevailing or strongest, wind or a region, accompanied by changes in precipitation patterns
(essentially it’s a wet season)
State 4 key features of a Monsoon
- Prevailing wind shifts 120 degrees between January and July
- Average frequency of prevailing winds >40%
- Speed of mean wind exceeds 3 m s -1 (10.8 km hr-1)
- Pressure patterns satisfy a steadiness criterion
Which are the main places which Monsoons will effect
Impacts India and Southeast Asia; intensities varies at different localities
Why do Monsoons occur?
The land is warmer during the summer, so evaporated water is pushed across the land
By 2050 UNESCO predicts that, x-y people living in urban environment will face water scarcity
What is x and y
1.7-2.4 billion
The UN estimates that demand for freshwater for human use will outstrip the supply by x% by 2030
x=40%
What are the potential consequences of demand for water outstripping supply
Crop failure = food insecurity
Mass migration = societal pressure
War = death and destuction
Health = dehydration and malnutrition
Is there more water use for domestic, or agriculture and industry use in the UK
Agriculutre and Industry
By 2050, available water could reduce by 10-15%
To make up for this deficit the UK government rely on
Extraction of ground water (abstraction)
However Government’s water abstraction plan shows 28% of ground water aquifers in England are being unsustainably abstracted
What is the UK water paradox
70% of the public believe the UK is a wet country with plenty of water
This belief can lead to wasteful habits which compound the issue
List some of the main impact of extreme events
- Loss of human/animal life
- Displaced people/migration pressures
- Health effects due to infrastructure failing or fires
- Disruption to ecosystem services
Why are cities more vulnerable to the urban heat island effect
As heat is absorbed more by buildings etc
What is the main trend in extreme events in the millennia
Increasing in frequency and intensity too
