Geography - Changing Climate

Climate change

the long-term change in global or regional climate due largely to increased levels of CO2 in the atmosphere

Quaternary Period

• a subdivison of geological time which covers the last 2.6 million years up to present day

• divided into two epochs

  • the Pleistocene (up 10 11,700 years ago)

  • the Holocene (about 11,700 years ago to present day)

• has been one of the extraordinary changes in global environment as well as the period during which much of which human evolution took place

General trend of last 2.6 million years

• average temperature has gradually decreased despite many fluctuations

  • fluctuations mostly small from 2.5 mmillion years ago until 1 million years ago

  • now larger fluctuations from 1 million years ago to present day

Fluctuating temperature

• over last 450,000 years, earth has remained in a glacial period below zero for the majority of the time

• around every 75,000 years, earth would enter interglacial periods and reached average temperatures as high as 6ºC at 0-60ºN and S

Causes of Natural Climate Change

1930s - mathematician Milankovitch agreed that climate change was linked to the way that the earth orbits the sun, how it wobbles and how it tilts

obliquity

changes in how earth tilts on it’s axis

• earth is tilted on its axis

• over arounf 400,000 years, the angle of the tilt changes slowly from 21.5º to 24.5º

• when earth is tilted towards the sun, we get our summer

• when earth is tilted away from sun we have winter

• with less tilts our summers are cooler anf winters are milder

procession

the amount earth wobbles on its axis

• as earth spins on its axis it wobbles

• wobble is causes by the force of gravity from the sun and the moon

• makes the axis trace a circular shape, meaning it slowly changes the direction it is pointing in

• the axis wobbles from one extreme to another over a period of ≈23,000 yers

  • this can change the severity of the seaons and which hemisphere is closest to the sun at points during the year

• earth’s wobble accounts for some regions of the world experiencing very long days and very long nights at certain times of the year

  • e.g. Northern Norway

eccentricity

changes in the shape of earth’s orbit

• the path of the earth as it orbits the sun

• orbit is not fixed - changes over time from being almsot circular to being mildly elliptical

• a complete cycal from circular to elliptical and back to circular occurs every 100,000 years

• orbital changes may have causes the glacial and interglacial cycles of the quaternary period

• colder periods occur when the earth’s orbit is more circular, and warmer when more elliptical

Sunspots

• dark spots on the sun’s surface

  • temporary and caused by magnetic storms

• the more sunspots there are, the more radiation earth recieves from the sun, causing temperatures to rise

• 11-year cycle of sunspot activity, although some cycles are longer

• the Little Ice Age (1300-1870) is linked to a time when there were few sunspots

• the Medieval warm period is linked to more sunspots

super volcano

• erupts more than 1,000km³ of material in a single event

• the eruption releases dust into the atmosphere

  • including ash, sulphur dioxide, and water vapour

  • this dust blocks sunglight, causing cooler temperatures on earth

• winds carry the dust across the globe, affecting areas far from the eruption site

Natural Greenhouse Effect - before human intervention

• natural process - vitally important as it keeps the earth warm enough to support life

• average temperature would be -18º rather than +15º

• gases in the atmosphere (e.g. CO2 and water vapour) are called greenhouse gases because of the way they act like a glass roof on a greenhouse

• they allow the sun’s radiation through and trap energy that is reflected back out

Enhanced Greenhouse Effect - after human intervention

• human process: putting more greenhouse gases into the atmosphere than naturally occuring

  • this makes the layer of greenhouse gases thicker and means more of the sun’s energy is trapped

  • this increases earth’s temperature and is causing climate change

Carbon Dioxide - CO²

causes:

• burning fossil fueld (coal, oil, natural gas)

• deforestation (stops CO² absorption + releases more into atmosphere)

• industrial processes e.g. cement making

global greenhouse emissions:

• CO² (burning fossil fuels) - 57%

• CO² (deforestation, decay of vegetation) - 17%

• CO² (other) - 3%

Methane - CH⁴

causes:

• vehicle exhausts

• agricultural and industrial processes (farming of livestock produces a lot of methane. rice paddies also contribute to global warming, because flooded fiels emit methane)

• burning of fossil fuels (coal, oil, natural gas)

• waste management (decomposing organic waste in landfill releases methane)

global greenhouse emissions

Methane - 14%

Nitrous Oxide - N₂O

causes:

• industrial processes (the production of nitric acid and adipic acid which are used in the manufacture of fertilisers, nylon and other products, are major industrial sources of nitrous oxide)

• agricultural processes (fertilised soils and waste contribute to nitrous oxide emissions)

• burning of fossil fuels

global greenhouse gas emissions

nitrous oxide - 9%

Global Impacts of Climate Change - Australia

specific impacts

• increased heatwaves

  • e.g. 2019-2020 summer was the hottest on record

  • temperature: average +1.52º above normal

  • consequence: more bushfires, stress on agriculture and human health

• more frequent and increased intensity bushfires

  • e.g. Black Summer Bushfires (2019-2020)

  • impact: burned around 18million hectares, killed or displaced 3 billion animals, destroyed over 3000 homes

  • economic cost: over 10 billion AUSD in damages

• rising sea levels

  • e.g. coastal areas of Queensland

  • impact: erosion and flooding affecting tourism and housing

• coral bleaching in the Great Barrier Reef

  • e.g. severe bleaching in 2016, 2017 and 2020 due to heat stress

  • impact: over 50% coral loss in shallow reefs

  • economic consequence: reef tourism employs 64,000 people and generayes over 6 billions AUD/year

• drought

  • e.g. Millenium Drought (1997-2009)

  • impact: crop failure, water shortages, increased food prices

economic impacts

• loss of imcome of tourism (great barrier reef damage)

• costs to rebuild after bushfires and floods

• agricultural loss from drought

social issues

• homes destroyed, people displaced by fires and floods

• health problems (heat stress, smoke inhalation)

• mental health issues in rural communities

environmental impacts

• wildlife killed in fires

• coral reef ecosystem decline

• coastal erosion damaging habitats

positive impacts

• warmer temperatures in some areas may extend growing seasons

• some crops (e.g. tropical fruits) could grow further south

UK Impacts of Climate Change

the top 10 warmest years for the UK since 1884 have occurred since 2002

in contrast, none of the coldest years have been recorded in this century

uk average temperatures have increased

• in early august 2020, at least twenty stations across southern england recorded maxiumum temperatures reaching 34ºc or more on six consecutive days

  • five ‘tropical nights’ were also recorded, when temperatues did not drop below 20º

  • the last time a similar event occurred was the summer of 1976, when at least twenty station recorded 32º or more for six consecutive days

• since the start of this century all but three years have recorded at least one tropical night

  • in contrast only half the years between 1961-2000 recorded tropical nights

coastal flooding

• about 30% of the UK’s population live within 10 miles of the coast

• the east of england which is relatively lwo-lying is most at risk of coastal flooding

• coastal regions contain lots of manufacturing, transport routes, power stations, oil and gas terminals and agricultural load

  • £120 billion worth of infrastructure is at risk from flooding

• more money will be needed for coastal defences e.g. sea walls

extreme rainfall and flooding

• in the UK it is likely that there will be more extreme rainfall in the future, especially in the winter

• heavy rainfall can cause flash floods to occur

  • these are floods that happen very quickly and have devastating effects

• damage caused by river and coastal flooding in the UK currently costs £1.3 billion per year

• by 2080 this is expected to rise to £12 billion a year

example - Flash Flooding in Tewksbury 2007

• in the summer of 2007 the UK suffered its wettest May and June since records began in 1776

  • there were floods across the country and widespread damage to homes, businesses and transport networks

  • the total cost to the UK’s economy was £3.2 billion

• some areas suffered more than others

  • Tewksbury in Gloucestershire was badly affected

  • on 20 July 2007, two months of rain fell in just 14 hours

  • three people died, 1800 houses were completely cut off and 50,000 had no electricity

  • a water treatment works was flooded leaving 135,000 houses without water for 17 days

• birds like the Lapwing and Redshank suffered when breeding grounds were flooded