Unit 2

• Atmospheric energy balance: the balance between incoming energy from the Sun and outgoing energy from the earth

  Energy transfers occur at 3 levels: top of the atmosphere, within the atmosphere itself and the surface of the earth 

  Atmosphere is an open energy system, receiving energy from both the sun and the earth. Incoming solar radiation is referred to as insolation. The energy that drives all weather systems and climates comes from the sun, generally absorbed at the equator, in tropic regions and lost at polar regions
• TOP OF THE ATMOSPHERE

  The Sun emits shortwave radiation. 70% absorbed by earth, 30% reflected by earth

  • Of the 30% reflected, 23% reflected by clouds and 7% reflected by earth’s surface
  • Of the 70% absorbed, 47% is absorbed by the earth’s surface, 19% absorbed by the atmosphere and 4% absorbed by the clouds
• WITHIN THE ATMOSPHERE

  Incoming energy from:

  • Absorbed shortwave by gases in atmosphere, clouds and from earth’s surface/ other smaller sources

  Outgoing energy:

  • Longwave emitted to space by clouds and by gases in atmosphere
  • Longwave emitted to earth’s surface by gases in atmosphere 
• AT THE EARTH’S SURFACE

  Incoming energy from:

  • Absorbed shortwave from sun
  • Absorbed longwave from gases in atmosphere

  Outgoing energy from:

  • Longwave emitted by surface of the earth
  • Further emitted directly to space, absorbed by atmosphere, emitted by clouds
  • Removal of heat by convection (rising warm air)
  • Heat required by evaporation and thus removed from the surface of the earth 
• Atmospheric energy balance

  → How:

  Earth's heat engine moves heat from the surface and lower atmosphere back to space.

  Earth's energy budget = flow of incoming and outgoing energy (has to be equal for the Earth’s temperature to remain stable in the long-term in a state of equilibrium)

  → Processes at 3 Levels:

  Surface of Earth: Main site for solar heating.

  Top of Earth's Atmosphere: Entry point for sunlight.

  Atmosphere in Between: Where energy processes occur.
• Natural Greenhouse effect: relationship between atmospheric GHGs & temperature of the earth’s surface. 

  1. As the concentration of atmospheric greenhouse gases in the troposphere increases, the temperature of the earth’s surface increases. (due to GH effect)
  2. Sun emits shortwave radiation- reflected into space or absorbed by the earth’s surface thus heating up the earth
  3. Earth emits longwave radiation- absorbed by GHGs
  4. Anthropogenic activity increases the amount of GHGs in the atmosphere, this causes global warming
• Milankovitch Orbital Cycles: changes in Earth's orbit that significantly impact the amount of solar radiation reaching the surface. These cycles influence the seasons and can contribute to the onset of ice ages. Ice ages occur when all 3 variables align, and the northern hemisphere experiences the least summer insolation.

  → Eccentricity: changes in Earth's orbit shape 

  • Goes from circular→ eclipse → back again: Due to the sun’s gravitational pull

  → Obliquity: variations in Earth’s tilt

  • Longer angle = larger difference between summer & winter

  → Precession: Earth wobbling as rotates
• Sunspots: cooler areas on the Sun's surface that increase the frequency of auroras when active. - bcos increased solar activity results in more charged solar particles reaching Earth, that leads to a higher likelihood of auroras  

  • More sunspots =  more radiation from the sun

  leading to hotter Earth & potential droughts. Solar radiation variations, including solar flaring, sunspot activity, and solar cycles, can alter the global energy balance by changing the amount of shortwave radiation entering the Earth's system.
• Solar dimming: The gradual reduction in the amount of direct sunlight reaching the earth’s surface 

  • Caused due to increased presence of aerosol particles in the atmosphere from human action
  • Aerosols+other particulates absorb solar energy & reflect back into space
  • Pollutants can become nuclei for cloud droplets. Water droplets in clouds coalesce around the particles 
  • Increased pollutants=more particulates, creating clouds that have many smaller droplets.
  • Makes clouds more reflective -> incoming sunlight being reflected back into space - Less reaching the Earth’s surface
• Volcanic eruptions

  • Major eruptions eject material into stratosphere
  • The sulphur dioxide forms a haze of sulphate aerosols, which reduces the amount of sunlight received at Earth’s surface
  • Volcanoes erupt - emit gases + particles into atmosphere
  • Some: cooling effect (ash, sulphur dioxide)
  • Others: warming effect (carbon dioxide) - exacerbate greenhouse effect
  • Eruptions can blast sun-blocking particles into stratosphere - temperatures drop
• Feedback Loops: a self-reinforcing mechanism in which a change in one part of the Earth system leads to further changes, amplifying or diminishing the initial impact. Positive feedback loops enhance the original change, potentially creating a runaway effect (bad), while negative feedback loops tend to counteract the initial change, maintaining system stability.
• Positive feedback loops: Occurs when a change in the state of the system leads to additional and increased change (Amplifying effect)

  • EXAMPLE - Melting Arctic Ice: As Arctic ice melts due to global warming, the Earth's surface becomes less reflective, absorbing more sunlight. This increases temperatures, further accelerating ice melt, which lowers reflectivity even more. This positive feedback loop intensifies the warming process, leading to a self-reinforcing cycle of increasing ice melt and temperature rise
• Some examples of positive feedback loops:

  Amazon rainforest die-off: Temperature rise > drought and wildfires increase in the Amazon > more trees die and decompose, or burn, releasing CO2 (causing temp rise again) > fewer rainforest trees mean less water pumped into the atmosphere > rainfall decreases

  Clogging the ocean sink: Temperature rise > warming waters shutdown exhange of CO2 from the surface to teh deep ocean > ocean waters dissolve less CO2
• Negative feedback loops: Helps the system go back to equilibrium - counteracting effect that contributes to stability
• Some examples of negative feedback loops:

  Surface temperature: Temperature increase > increased evaporoation from the oceans > more low clouds in the atmosphere > reflects more sunlight back into space > surface temperature decreases

  Carbon Cycle Feedback: Temperature increase > increase in the rate of organic matter decay and soil respiration > releases more carbon dioxide (CO2) into the atmosphere > plants photosynthesize more efficiently > absorbing and storing greater amounts of carbon, offsetting the increased carbon emissions, acting as a negative feedback loop
• Terrestrial Albedo

  Albedo is the portion of solar radiation that is reflected from a surface.

  Alterations in the reflective properties of Earth's land surfaces. Changes in land cover, such as deforestation or urbanization, can influence albedo. 
• Terrestrial Albedo Example: replacing reflective surfaces like snow or vegetation with darker surfaces like asphalt or bare soil lowers albedo. This affects the amount of sunlight reflected back into space, contributing to regional and global climate changes.
• About Terrestrial Albedo

  • Measured as: the percentage of sunlight (across all wavelengths) that is reflected by a surface compared to the total sunlight incident upon it. 
  • An object with an albedo of 100% would reflect all incoming sunlight , while an object with an albedo of 0% would absorb all incoming sunlight.
  • Higher albedo = higher reflectivity 
  • Corresponds to latitude 
  • Higher latitudes experience more snow + ice that reflect light, -> higher albedo values. 
  • Seas have low albedo and reflectivity 
  • Surface albedos increase with distance from the equator 
• Methane gas release and feedback loops

  • Livestock emissions contribute greatly to global warming through the release of methane 
  • A cow does on overage release between 70 and 120 kg of Methane per year
  • Agriculture is responsible for 18% of the total release of greenhouse gases worldwide (this is more than the whole transportation sector). 
  • The clearing of tropical forests and rain forests to get more grazing land and farm land is responsible for an extra 2.8 billion metric tons of CO2 emission per year
• Examples of Methane Positive Feedback Loops:

  Warming wetland peat: Temperative rise > warming wetland peat > bogs release methane, a greenhouse gas > more heat absorbed by the atmosphere

  Melting permafrost: Temperature rise > permafrost bogs thaw > bogs release methane a greenhouse gas > more heat absorbed by the atmosphere

  Subsea floor methane hydrate: Temperature rise > ocean warming > sea floor sediment warms and methane hydrate melts > some methan vents to air above sea surface
• Enhanced greenhouse effect

  Where the natural processes of warming caused by solar radiation and greenhouse gases are heightened by anthropogenic factors. 

  • The disruption to Earth’s chemical equilibrium caused by the increased concentrations of greenhouse gases has led to an increase in the global average surface temperatures

  GLOBALLY: Higher GDP per capita generally = higher CO2 emissions per capita globally. 

  • An Oxford study reveals that the wealthiest countries (high and upper-middle income) constitute half the population but contribute to 86 percent of emissions on a production basis.
• International variations can be attributed to:  

  1. Economic development:-The only spontaneous decrease in emissions happens in the time of economic crisis, e.g. Great Depression. 
  2. Globalisation: set of processes that contribute to the relationship between societies & individuals

  • -Regions of greater globalisation emit more GHG
  • Larger globalisation, countries more industrialized + have more TNCs. Promotes global production=global emissions. 
  • main sources of CO2 emissions: industrial production, transportation, deforestation

  1. Trade: buying & selling of goods/services between diff countries
• What if all the ice melted on earth?

  Only 3% of the world's water is fresh, with 70% of that frozen in glaciers, ice sheets, and icebergs. Melting sea ice due to rising temperatures harms marine life and triggers more seismic blasting for oil exploration, further impacting marine ecosystems. 95% of Earth's ice is land-based, primarily in Greenland and Antarctica. Sea levels could rise by 70m, displacing an estimated 1.4 billion people. Ice melt contributes to global warming, potentially disrupting ocean currents and affecting global temperatures, leading to challenges like crop growth.
• Greenland’s melting ice sheet

  • Polar regions are more sensitive to global warming, so Greenland is especially affected 
  • Greenland has more land ice than any other place except Antarctica
  • If all melted, sea levels could rise by 6m
  • Greenland ice sheets release 250 gigatones of water into the ocean every year
  • Extra freshwater from melting ice change circulation patterns in the ocean and atmosphere 
  • Greenland’s ice sheet melting could impact weather patterns far away
• Antarctica’s ice sheet

  • Antarctica’s ice is on the move 
  • Majority of the ice exists as ice sheets that move towards the sea due to gravity
  • Continue to move as ice shells that drift across the sea
  • Researchers drill cores of ice to investigate antarctica’s climate history
  • Ice cores contain air bubbles that reveal climatic patterns from the past (100,000 years back in time)
  • Records from rock layers detail Antarctica’s ice history from 1 million years ago 
  • But these rocks are very hard to find as they move as ice moves
• → Melting icebergs

  • Land ice melting has a bigger impact on water levels, however, sea ice melting can also have an impact
  • Fresh water (icebergs) is less dense than salty water
  • Means that melted freshwater will take up a slightly larger volume than the displaced salt water > Results in a small increase in water level 
  • While global sea-level change from floating ice is small, it is detectable in a regional sense 
• → Impacts of sea level rise (negative)

  • Increased risk of flooding (coastal, low-lying, islands)
  • Migration - climate-induced displacees, eg. Bangladesh (forced migration) 
  • Coastal erosion and loss of land

  More money has to be invested into coastal protection and the cost of movement / management

  • Salinity increases in estuaries, deltas 

  Negatively impacts biodiversity - loss of habitat 

  • Damage to mangroves and coastal ecosystems 
  • Tropical storms - greater frequency and intensity caused by warmer oceans 
• → Impacts of melting sea ice (positive possibilities)

  • Freshwater supplies
  • Improved transportation

  Transport routes are quicker, particularly for ships which are not obstructed by large icebergs

  • Resource extraction easier
  • Increased fishing opportunities 
• Glacier melt

  • Ice acts as a protective cover over our Earth and oceans, bright white spots reflect reflect excess heat back into space, keeping the planet cooler
  • Glaciers range from several hundred to several thousand years old, provide a scientific record of how climate has changed over time
  • Around 10% of land area on Earth is covered in ice
• Effect of Glacier Melt

  • Melting glacial ice entering warmer oceans slows currents, raising sea levels and causing coastal erosion. The runoff increases ocean water, elevating warm surges & intensifying coastal storms. Dark patches emerging as ice melts reduce the cooling Albedo effect
  • As warmer water change when and where fish spawn, affects fishing industries
  • Coastal communities become more vulnerable as flooding becomes more frequent and storms become more intense
  • Warmer ocean temperatures- sea ice melt -Causing higher rates of conflict between animals and people
• Store of carbon - Carbon pools or reservoirs or stocks 

  • Any movement between these pools is known as a flux
• Outline the relationship between carbon sources and carbon sinks. 

  • Sources add carbon to the atmosphere, while sinks remove it (store it).
  • If all sources are equal to all sinks, the carbon cycle is said to be in equilibrium
  • Maintaining a steady amount of CO2 in the atmosphere helps maintain steady average temperatures at a global scale  
• How does the carbon cycle link into the atmospheric energy budget?

  • The carbon cycle has a large effect on the function and wellbeing of the planet
  • The carbon cycle plays a key role in regulating the Earth’s climate by controlling CO2 concentrations in the atmosphere
  • CO2 then contributes to the greenhouse effect, where heat generated from the sunlight at the Earth’s surface is trapped and escape through the atmosphere is prevented  
  • Risen to 30% above natural background levels 
• Four major carbon pools`

  1. The Earth’s Crust
  2. the largest amount of carbon on Earth is stored in sedimentary rocks within the crust 
  3. Oceans

  • Most in the form of dissolved inorganic carbon at great depths

  1. Atmosphere

  • Mostly in the form of CO2
  • Smaller amounts in methane (CH4)
  • Before fossil fuel combustion and deforestation 
  • More sensitive to increases in carbon in other pools

  1. Terrestrial ecosystems

  • Woody stems in trees have the greatest ability to store large amounts of carbon: Via photosynthesis
• Extreme Weather Events

  Is climate change causing more extreme weather?

  • Using climate models, the likelihood of an increase in extreme weather due to climate change can be estimated with greater accuracy
  • But there are high levels of natural variability 
  • The warmer the sea surface, the more water evaporates
  • The intensity of storms are increasing over the decades 
  • But correlation does not imply causation - climate change does not necessarily cause more extreme hurricanes

  1. Hurricanes, typhoons and tropical cyclones (all the same thing)
  2. Heat Waves
  3. Storms and flooding
  4. Drought
• Crop yields 

  • Warming planet = Larger swarms of hungrier insects eating rice, maize and wheat crops → This occurs as rising temperatures increase metabolism, which makes them eat more
  • The world demand for these crops is set to increase by a third by 2050 → Leads to a rise of food prices, causing food-insecure families to suffer
  • Climate change has caused some crop yields to grow
  • Biome shifts have also led to places becoming cooler and a subsequent increase in agricultural production 
  • Short term solutiojn - Breeding or cultivating crops that are resilient, or benefit from climate change
• Global hunger rise

  • Decreases in consumable food calories are already occurring in roughly half of the world’s food insecure countries
  • The number of undernourished people in the world has risen since 2014, to an estimated 821 million in 2017
  • MEDCs can lessen the effects of food calorie shortages by importing food, but poorer countries cannot
• → Food supplies

  • Climate change has changed in yields in many places, some positively, others negatively 
  • Reduced global rice yields by 0.3% & wheat yields by 0.9% on average each year 
  • Overall reducing global production of staple foods, especially rice and wheat 
  • Is shrinking food supplies, specifically in food-insecure developing countries 
• → Soil erosion

  • Soil contains small animals, fungi, bacteria, hence damage to soil health affects biodiversity
  • We rely on healthy soil for 95% of crops we eat (Healthy soil can be a major sink for carbon
  • Formed: From rocks that are decomposed slowly from sun, wind, rain, animals and plantsx
  • 500 years to naturally build an inch of topsoil - losing at 17x that rate
  • 33% of worlds soil has been degraded 
  • Soil can hold 3X as much carbon than forests and other vegetation
  • 8.4 billion per year for soil erosion control - though it causes 44 billion in damage each year
• How does human activity affect soil erosion?

  • Deforestation: 13 million hectares of forest are cut down 
  • Industrial agriculture: Monocultures and farming on slopes 
  • Monoculture: the cultivation of a single crop in a given area Accelerates erosion
  • Intensive cultivation and mono cropping- when soil is turned, topsoil is decemated - airaets the soil
  • Cultivation of soil results in decreasing fertility
  • Modern agricultural techniques: Intensive cultivation leads to a decline in soil quality 
  • Urbanisation: Soil buried by impermeable materials like concrete