1a - Global Climate Systems Flashcards
What causes different pressures of air?
Warm, less dense, rising air = low pressure resulting in condensation, clouds and precipitation
Cool, more dense sinking air = high pressure resulting in no condensation, clouds or precipitation
Describe the process of global atmospheric circulation?
- At the equator, ground is intensely heated by sun, causing the air to rise creating low pressure zones
- The now cool air moves out to 30 degrees N/S of the equator where the air cools & sinks forming subtropical high pressure zones
- Some of the air completes the cycle flowing back towards the equator as trade winds, completing the Hadley cells
- The rest of the air moves towards the poles, called westerly trade winds, and at 60 degrees N/S of the equator, the warmer surface winds meet colder air from the poles
- The less denser warmer air rises as the two air masses meets and at the poles the air is cooled and sinks towards the ground forming high pressure
What are the circulation cells?
Hadley cell - prompted by rising air at the equator
Ferrell cell - prompted by rising air at the mid-latitudes when warm air meets cold air
Polar cell - prompted by descending air at the poles which return to meet warm air the mid-latitudes
What are causes of different types of rainfall?
Convection rainfall - rising air condenses and cools
Frontal rainfall - two air masses meet, warm air rises over cold air, condenses and cools
How do ocean currents transfer and redistribute heat energy?
Ocean currents are large scale movements of water that transfer heat energy from warmer to cooler regions
Surface currents are caused by winds and transfer heat away from the Equator
There are also deep ocean currents driven by differences in water density - when water freezes at poles, surrounding water gets saltier increasing its density
Then it sinks, causing warmer water to flow in at the surface creating a current
The warmer water is cooled and sinks continuing the cycle
How are arid/dry zones formed?
Sinking air at the Hadley and Ferrel cells (30 degrees N/S) cause high pressure and prevents rainfall. Temperatures are hot/warm
How are polar zones formed?
Sinking air from the Polar cells create areas of high pressure at the poles causing very little rainfall. There is low temperatures all year round
How are Tropical zones formed?
Rising air from the Hadley cells create low pressure areas which cools, condenses and precipitates resulting in lots of rainfall. Temperatures are hot all the time - due to strong concentration of sun - and rainfall is high
What is climate change and when has it changed?
Climate change is natural, long term process where there is any significant change in the earth’s climate
During the Quaternary period (from abt 2.6m years ago) the climate has varied significantly from warm interglacials and cold glacials
What are the natural causes of climate change?
Orbital changes
Volcanic activity
Asteroid collisions
Solar output variations
How have orbital changes caused climate change?
The Earth’s orbit around the sun changes over time, meaning it receives more/less heat. There are 3 cycles:
Eccentricity/stretch - the Earth’s orbit changes from a circle to more of an eclipse which happens over a 100,000 year cycle
Obliquity/tilt - the Earth is tilted on its axis and the angle changes from 22.1 to 24.5 degrees on a cycle of every 41,000 years
Precession/wobble - the Earth wobbles on its axis, meaning that different parts of the Earth are closer to the sun in sumar
How has volcanic activity caused climate change?
Major volcanic eruptions eject large quantities of material into the atmosphere
Some of these gases help heat the planet whilst other gases and ash cool the planet by blocking out the sun and reflecting the sun’s rays
How has asteroid collisions caused climate change?
Asteroids hitting the earth could push huge amounts of material into the atmosphere which can prevents and blocks the Sun’s energy from reaching the Earth’s surface, cooling temps
How has solar output variations caused climate change?
The amount of energy produced by the sun varies because of sunspots, which work on an 11 year cycle
Periods of reduced solar outputs lead to cooler climates
What methods are evidences for climate change?
Tree rings
Ice cores
Historical sources
How do tree rings determine climate change?
Most trees produce one ring within trunk every year
The greater the thickness/width of the ring, indicates better growth and higher temperatures/more CO2 & vice versa
Scientists take cores through each tree trunk then date each ring by counting them back from when the core was taken
How do ice cores determine climate change?
Ice sheets are made up of layer of ice - one layer formed per year
Scientists drill into ice sheets to get long cores of ice
By analysing the gases ,eg co2, trapped in the layers they can tell the temperature each year
Ice cores analysed to determine amount of CO2 in them. With higher concentrations associated with wamrer/inter-glacial periods
How do historical sources determine climate change?
Thermometers have been used since the 1850s to measure global temperatures accurately
Diaries, newspapers, journals, paintings inform us about the conditions of the time which allows to compare former to current (warmer/colder)
How have evidences for natural climate change been used to reconstruct glacial and interglacial climate during the Quaternary and UK climate since Roman times?
Medieval warm period - period of relatively high temps between 900 & 1300
Harvest records shows that England was warm enough to grow large quantities of grapes
Tree rings data suggests this was also the case during the roman times, when temps were almost 1 degree warmer than today
Little Ice age - period of cooling following Medieval Warm Period
Paintings from 17th century shows London Frost Fairs, which took plane on a frozen river thames
Historical records talk about Arctic ice reaching as far south as Scotland
What is the natural greenhouse effect and how does it work?
The temp of the Earth is a balance between the heat it gets from the Sun and the heat it loses to space
1. Sun’s energy arrives as short wave radiation which travel through the greenhouse gases
2. This energy is reflected off the Earth as long-wave radiation and this is unable to pass through the greenhouse gases so is reflected back to Earth
Gases that trap heat are GHG eg co2, methane - the longer these stay the more they contribute to warming
How do human activites produce GHG that cause the enhance greenhouse effect leading to global warming?
Energy - CO2 released into atmosphere when fossil fuels like coal, oil and natural gas are burnt
Transport - travelling in petrol/diesel vehicles releases nitrous oxides and some CO2 & electric cars require power generation which is mostly from fossil fuels
Farming - deforestation of land for agriculture stops trees absorbing CO2 & farming of cattle produce large amounts of methane when digesting food , fertilisers give off nitrous oxides
Industry - industries use lots of energy, some industrial processes produce GHG eg cement production releases CO2 & industrial waste may end up in landfill sites where it decays releasing methane
State 4 evidences for how human activity is causing climate change
Sea level rise & warming ocean
Global temp rise
Declining Arctic ice
Increased extreme weather events
How does sea level rise & warming oceans act as evidence for humans causing climate change?
Thermal expansion - water in the ocean expands as it gets warmer & scientists think this accounts for about half of the measured rise in sea levels
Eustatic sea level rise - warmer temps cause glaciers to shrink and ice sheets to melt. The melting of ice on land means that water stored on land as ice returns to the oceans.
How does declining arctic ice act as evidence for humans causing climate change?
Sea ice forms around the poles in winter when ocean temperatures drop below -1.8degrees and melts in the summer when it’s warmer
The extent of arctic sea ice in winter has decreased by >3% each decade over the past 35 years
