Unit 5 Weather and Climate

extreme weather events

what is extreme weather?

when a weather event is significantly different from the average ususal weather pattern for a partciular location

what are examples of extreme weather events?

• drought (california central velley, Ethiopia)

• flash floods (Bostcastle)

• strong winds and tropical cyclones (Bangladesh Cyclone Ampham)

• extreme heat wave (1976 UK drought)

• extreme cold spell (2010 Beast from the East)

what is believed to be the driving force behind much of the increased extreme weather events?

anthropogenic climate change

however, what is another reason for extreme weather?

due to natural cyclical variations in our climate

NATURAL VARIATIONS IN CLIMATE:

What are El Nino and La Nina events

• natural changes to the normal ocean currents and atmospheric circulation in the Pacific Ocean.

• occur ever 3-8 years and can affect weather on a global scale

What is the La Nina event?

this is a more extreme version of the normal conditions above. the low pressure is lower and the high pressure is higher

what is the global impact of El Nino?

• In the pacific ocean, stronger hurricanes occur

• northern states and the pacific northwest become warmer and drier than usual

• areas of south america experience heavy rains

The 2015/16 El Nino related extreme weather events:

are countries affected by El Nino equally vulnerable and resillient to the effects of these events?

While many countries are impacted by El Nino, their vulnerability and resilience vary based on factors like infrastructure, preparedness, and economic stability.

e.g. Ethiopia v California

• are El Nino events becoming more common/severe?

• becoming more severe

• the severity of the events are on an upward trend

• intensity seems to be greater especially in eastern El Nino events

• rise in central pacific el nino events

Latest El Nino event: 2024 El Nino: Extreme rainfall in Suth America

• between 24 April and 4 may 2024, over 420mm of rain fell in Brazil’s southermost state RIo grande do Sul

• this led to 90% of the state being affected by flooding

ANTHROPOGENIC CLIMATE CHANGE AND EXTREME WEATHER:

what are the predictions of extreme weather that are linked to climate change?

• more extreme rainfall e.g. VALENCIA, SPAIN 2024

• extreme heat and record droughts

• more cyclones and tropical storms as sea surface temps are increasing

The evidence for Extreme Weather Events?

(rise in temoperatures)

• since 1900 the average temperature has risen by 1.2 degrees

• 19 of the hottest years have occured between 2000-2024

• 2024 was the hottest year on record since 188- with avg temp 1.5 degrees above long term average

as the world’s climate warms what will happen to the probability of heat extreme weather related events occuring?

the probability will increase

some areeas will experience wetter conditions and some will experience drier conditions

change in extreme natural events:

what is the change for geophysical events?

quite stable and arent on an upward trajectory

what is the change for meteorological/hydrological/climatological?

fluctuating yet there is an upward trend

• 1980-200

• 2019-800

REGIONAL EXAMPLES OF EXTREME WEATHER:

1. EUROPE-flooding,storms and heatwaves

what is the pattern of extreme weather within different regions within Europe?

• North-western Europe will experience increased winter storms, precipitation and increased risk of flooding

• The Mediterranean region will experience drier conditions, more heatwaves and forest fires (e.g. Greece) - decrease in annual precip, increasing risk of desertification

UK EXTREME WEATHER EVENTS (causes and impacts)

1. cause of extreme weather: cyclonic storm

IMPACTS:

• cause major damage to the south of the UK

• low pressure storm

• high wind speeds of >120mph

• roofs torn off

• damage to property and infrastructure

• leads to fromation of waves >11m high

EXAMPLES:

Storm Eunice

Storm Dudely

Storm Franklin in Feb 2022

2. cause of extreme weather: convective storms

hazards:

• intense rainfall (convectional rainfall)

• hailstorms can occur

• thunderstorms

IMPACTS:

• damage to homes

• death

• impacts on agriculutre

EXAMPLES:

June 2016 Southern Netherlands hailstorms (up to 5cm hail stones which cost insurers up to $1 billion)

3. causes of extreme weather: winter anticyclones?

high pressure systems which can lead to frost and snow in the winter

EXAMPLES:

Beast from the East 2018- temps dropped as low as -14 degrees

4. causes of extreme weather: summer anticyclones

IMPACTS:

• low river levels

• can push other weather systems from the UK

• heat stroke

• infrastructure affected (heating of railway lines causing them to change shape)

• tarmac melting which has to be repaired.

EXAMPLES:

summer 2022 heatwave in the UK temps reached 40.3 degrees

1976 drought- extended period of high temps

REGIONAL EXAMPLES OF EXTREME WEATHER:

2. European heatwaves, droughts, forest fires, and floods

what were the physical impacts of the 2023 heatwave?

low river flows and lake levels:

• the River Danube fell to its lowest level in 100 years. Reservoirs and rivers used for public public water supply and hydro-electric schemes either dried up or ran extremely low

FOREST FIRES:

• The lack of raindall meant very dry conditions leading to forest fires e.g. In Portugal 215,000 hectares of forest were destoryed

MELTING GLACIERS:

• extreme snow and glacier melt in the European Alps led to increased rock and ice falls in the moutains

what were the human impacts of the 2024 heatwaves?

• 47,000 people died due to the heat in Europe (mainly Greece, Bulgaria and Spain)

to what extent are these heatwaves a result of climate change? 1976 v 2022

• 35.9 degrees in 1976 (max temp)

• 38.1 degrees in 2022

• Higher temps are much more widespread across the world in comparison to 1976

CASE STUDY: NOV 2024 FLOODS, VALENCIA SPAIN

what were the impacts?

more than 200 dead

billions of euros of economic damage

what caused the flood and how is it linked to climate change?

• caused by a destructive wind system called DANA

• rise in Mediterranean and global air temps may lead to a rise in the frequency of floods like this. (warmer air can hold more water vapour)

• lots of moutainous regions in spain leading to lots of orographic rainfall

3. TROPICAL CYCLONES

what evidence is there that tropical cyclones are becoming more severe?

• warmer ocean temperatures

• climate models (show increasing category 4-5 storms)

• sea levels rising

• rising global temps as warmer air can hold more water vapour

what is the future pattern and severity of tropical cyclones in future?

• records for hurricanes keep getting broken in terms of wnd speed, precipitation, storm surges (shows rising severity of storms)

• e.g. in 2017 Storm Ophelia formed further northeast than any other Category 3 Atlantic Hurricane

what major cities could experience tropical cyclones in the future as a result of warming oceans?

cities like New York, Tokyo and Beijing may be at risk as cyclones are forming further north than normal

Vulnerability to tropical cyclones and extreme weather: Small island states

CASE STUDY: VANUATU, South west pacific ocean

key information?

• home to 260,000 residents, constitutes 82 volcanic islands many of which sit 0.9m above sea level

• sea level rise in this region is 3mm per year

• ocean acidification and temperature rise threaten coral reefs. Coastal fishing is vital to them as it provides nutrition, welfare and employment (between 1990 and 2018, total fisheries production has decreased by as much as 75% in Vanuatu)

how is extreme weather affecting this area and what will it lead to?

• Cyclone Pam which hit Vanuatu in 2015, destroyed 96% of the islands food crops and caused economic damage to equivalent of 64% of the country’s GDP and left 75000 people homeless

• Cyclone Harold in Apirl 2020 left 87,000 people homeless

IN FUTURE:

• cyclones will become more severe endangering the country’s economy and the population’s livelihood.

why are countries such as Vanuatu so vulnerable to Tropical Cyclones?

• sea surface temps and ocean heat are increasing more than global average

• sea levels rising also threatens the future of low lying islands whilst increasing ocean heat and acidification harms vital and vulnerable marine cosystems

• economy based on agriculture and provide income for >70% of population

CASE STUDY: THE MALDIVES, INDIAN OCEAN

key information?

• home to over 500,000 people

• Maldives are 1200 islands- 80% are less than 1m above sea

• the growth of tourim: accounts for 28% of GDP. Yet it depends on the very beaches which wlll be eroded away by cyclones and submerged by rising seas

• fishing is the second most important industry; employs over 20% of the population but this is threatened by coral bleaching

Reducing vulnerability to the Threats of Climate

what strategies/infrastructure has been put in place?

• Male, the capital is surrounded by a 3m high wall (took 14 years to construct at the cost of $63m) Japan paid for 99% of the cost THEREFORE it is dountful that the government could repeat this scheme for other less strategic islands (ADAPTATION)

• The Maldives have been constructing a new island, New Male, to which it hopes to be able to transfer 120,000 people from its lowest lying islands. this island will be 2.1m above current sea level. HOWEVER, this will not provide a permenant solution if sea levels continue to rise

will the Maldives be resilient to increased climate change induced extreme weather in the future?

• constructing new island thats built to a height of 2m

• Male has a wall built around it of about 3m

• there maybe more resilient but there would be a severe loss in the economy of tourism

REGIONAL EXAMPLES OF EXTREME WEATHER:

4. Asia- dramatic weather variability

what is a consequence of climate change in regions like this?

• the dramatic shifts between weather extremes.

where has this concept been experienced?

In the Indian subcontinent:

• 2016 saw a drought that affected over 330 million people from the failure of the monsoon rains

• 2017 was a year of record rains leading to flooding

what were the impacts of this extreme rainfall?

• more than 16 million people have been affected by monsoon flooding across the South Asian countries of India, Nepal and Bangladesh

• one-third of Bangladesh and Nepal have been flooded

• All three countries face severe food shortages and disease caused by polluted flood waters

• more than 400 people have died in the three countries

why are many of the affected people so vulnerable to these events?

• these floods wipe out farmland, which takes away the farmers’ main source of income

• food prices go up

• roads become damaged

CHANGING VULNERABILITY OF POPULATIONS TO EXTREME WEATHER:

Are all people equally susceptible and vulnerable?

1. Climate Change and Human Displacement

• people dont have the financial means to get home

• Bangladesh- up to 7km of roded land along coasts and rivers. Displaced 100,000 of people

• in the Maldives, Hathifushi island saw storms that flooded the island up to 1m, the isolation and soil salinisation saw 295 residents pem=rmenantly evacuated

• forces millions of people from there homes e.g. Maldives and Vanuatu.

2. Extreme weather as a cause of poverty

• up to 325 million people will be living in countries highly exposed to natural hazards by 2030

• agriculturally dependent countries may see poverty e.g. Ethiopia

• in sub saharan Africa, 118 million people on poverty will face extreme weather events

• in drought prone areas, drought is the key cause of impoverishment

• moeny tends to flow to the diasters not to the poor people

3. Adapting to extreme weather arounf the world

ROAD RAISING IN MIAMI

Road raising in Miami Beach: a strategy to mitigate flooding and enhance resilience against sea-level rise and storm surges.

• the city also installed new pumps that can remove up to 75,000 litres of water per min. also implemented minimum heights of sea walls

Natural sea walls in Indonesia

• building 9km of semi-permeable sea damns, made from bamboo poles and brushwood, to mimic the role of mangrove roots whuch trap sediment and create favourable conditions for the trees to grow back naturally

• within the first year, sediment built up by 45cm and new trees appeared

Cheap cooling in South Africa

• cool coatings of paintings (reflect high % of sun)

• makes low income housing resistant to heat

salt tolerant crops in Bangladesh

almost 35 million people affected by soil water salinity

• certain variety of carrot, potato and cabbage plants have been found to be better suited to the salty soil.

• ICCO cooperation has been working with 10,000 farmers in Bangladesh

what are other management strategies?

• storm shelters

• modification of crops

• Smart drip irrigation of crops

• Grand Reneissance Dam

• New Orleans flood management (hard and soft engineering)