2.4 The human impact

Question 1

What is the enhanced greenhouse effect?

Answer 1

• Greenhouse gases allow more solar radiation to pass through Earth’s atmosphere
• Earth absorbs most of the radiation and warms up
• Earth radiates heat energy
• less heat escapes into spacce
• more heat is absorbed by greenhouse gases in the atmosphere
• greenhouse gases radiate heat in all directions
• the lower atmosphere heats up

Question 2

What is the evidence for the enhanced greenhouse effect?

Answer 2

• **CO2 (315ppm 1950 400+ppm 2020) **
• Methane (increases at 0.5-2% per year : (from cattle and as perma-frost melts)
• CFCs (increases 6% each year): 10,000x more efficient at preventing longwave radiation from penetrating as CO2 (used as refrigerants aerosol propellants). Also destroys ozone, allowing more insolation to enter the atmosphere
• Nitrous oxides (increased by 8%)
• Rising sea levels (3.1mm per year)
• Ocean acidity (26%acidity increase since 1750)
• melting ice and glaciers - arctic ice sheet shrunk by 65% since 1975

Question 3

What are the natural causes of global warming?

Answer 3

Natural factor: Volcanic activity:
- eruptions responsible for global cooling due to ash and sulphur released which reflect some of suns rays back into space

Natural factor: SOLAR OUTPUT:
-increases in sun spots can result in global warming

Natural factor: MILANKOVITCH CYCLE:AXIAL TILT
- tilt can reduce amount of solar energy reaching Earth’s surface, so over time winters get warmer and summers cooler

Natural factor: MILANKOVITCH CYCLE: ECCENTRICITY:
- approx every 100,000 years shape of earths orbit changes
- change impacts amount of sunlight reaching Earth’s surface and differences between seasons
- elliptical - distinct seasons
- circular = less distinct

Natural factor: MILANKOVITCH CYCLE: PRECESSION
- axis of Earth not fix and actually wobbles slightly
- results in greater seasonality

Natural factor: LA NINA AND EL NINO CYCLES
- heats the planet as normal westward surface flow of currents reverses and warm water moves east which causes high temperatures and drought in Australia and heavy rainfall in Peru.
- La Niña produces colder years as a result of cool upwellings off the Peruvian coast.

Natural factor: CONTINENTAL DRIFT:
- altering ocean currents: shift temp/precipitation patterns
- changing landmass distribution

Question 4

What are human causes of global warming?

Answer 4

• nitrous oxide from fertilisers
• CFCs from refrigerators
• methane from cattle
• CO2 from fossil fuel burning/deforestation

Albedo change:
- deforestation and urbanisation has resulted in more, much darker surfaces, so the ground absorbs more radiation, which is released back to the atmosphere – heating it.

Question 5

What are the atmospheric impacts of global warming?

Answer 5

• warmer temps lead to more evaporation from oceans, increasing moisture in atmosphere, lead to increased cloud/rainfall in places, cause local cooling
• warmer temps in places with high pressures, e.g south-west USA, cause less rainfall; result in more severe droughts
• heat waves occur especially in cities; because urban temps are always higher than surrounding rural areas
• more frequent/more violent storms expected; because of greater moisture in warmer air/more coastal flooding from storm surges
• melting arctic sea ice and loss of snow cover; result in less reflection of solar radiation and more heating of atmosphere; so accelerating global warming

Question 6

What are the other impacts of global warming?

Answer 6

• Sea Levels: 200m people could be displaced, 4 million km2 of land threatened by floods, 200m at risk from flood/droughts.
• Warming oceans: 50% increase in marine heatwaves this decade
• Storm Activity: more frequent and intense hurricanes, tornadoes
• Agriculture: USA’s grain belt will decrease, China’s growing season will increase, Northward shift for timber and crop production
• Drought: reduced rainfall in Europe and USA will expose 4bn to water shortage risks
• Disease: 60 million more people exposed to Malaria, as mosquitos breed faster in the heat
• Wildlife: 40% of species will become extinct at +2°C
• Tourism: previously undesirable areas may become tourist hotspots, and likewise for desirable places becoming undesirable.

Question 7

What human factors cause humidity in London?

Answer 7

1. Urban Heat Island Effect:
   - Central London and highly urbanized areas tend to be warmer than suburban areas due to the urban heat island effect, where buildings, roads, and other infrastructure absorb and retain heat.
   - Higher temperatures can lower relative humidity levels, as warm air can hold more moisture.
2. Vegetation and Green Spaces:
   - Urbanization leads to the replacement of natural vegetation with impermeable surfaces such as roads and buildings.
   - This reduces the amount of moisture released into the air through transpiration by plants.
   - Conversely, efforts to increase green spaces and plant more trees in urban areas can help to moderate humidity levels by enhancing transpiration.
   - so areas such as Hyde park and regent’s park may have high humidity
   -
3. Proximity to the Thames River:
   - Areas closer to the Thames River, such as central London (e.g., South Bank, Westminster), generally experience higher humidity levels due to the evaporation of water from the river.
   - The presence of the river can also lead to more fog and mist, especially during cooler months.
4. Transportation and Industrial Activities:
   - Vehicles and industrial processes release water vapor as a by product of combustion and other activities. This contributes directly to the local humidity.
5. Climate Change:
   - Human-induced climate change affects global weather patterns, including those in London.
   - Changes in temperature and precipitation patterns can influence local humidity levels.
   - Warmer global temperatures may lead to increased evaporation rates, which can raise humidity levels.
6. Domestic Activities:
   - Activities such as heating, cooling, and the use of household appliances (e.g., humidifiers, showers, cooking) contribute moisture to the indoor and sometimes outdoor environment, affecting local humidity levels.

Question 8

What human activities effect temperature in London?

Answer 8

1. Urban Heat Island Effect (UHI):
   - occurs due to the concentration of buildings, roads, and other infrastructure that absorb and retain heat.
2. Transportation:
   - emissions from vehicles contribute to higher temperatures in cities.
   - The combustion engines release heat directly into the atmosphere.
   - Additionally, traffic congestion leads to more idling vehicles, which further increases heat output.
3. Industrial Activities:
   - Factories and industrial processes generate significant amounts of heat through machinery and the release of hot gases.
4. Energy Consumption:
   - The widespread use of heating, ventilation, and air conditioning (HVAC) systems in homes, offices, and commercial buildings releases heat into the environment.
   - Power plants, particularly those burning fossil fuels, contribute to the overall heat output.
5. Building Design and Infrastructure:
   - design and density of buildings affect temperature.
   - Tall buildings and narrow streets can trap heat, reducing airflow and leading to higher temperatures.
   - Reflective surfaces and dark-coloured roofs absorb more heat compared to lighter, more reflective surfaces (lower albedo).
6. Reduction of Vegetation:
   - Urbanization often leads to the **removal of trees and green spaces, which are natural cooling agents.
   - Vegetation provides shade and cools the air through the process of evapotranspiration.
   - The loss of green spaces exacerbates the UHI effect, leading to higher urban temperatures.
7. Waste Heat Emission:
   - Various urban activities emit waste heat, including industrial processes, electricity generation, and even human metabolism. This cumulative waste heat contributes to higher urban temperatures.

Question 9

What human activities effect precipitation in London?

Answer 9

1. Urban Heat Island Effect (UHI):
   - increased heat from urban areas can cause rising air, which may lead to localized convection and potentially more rainfall in and around the city.
   - This localized heating can lead to the formation of clouds and precipitation as the warm air rises, cools, and condenses.
2. Air Pollution:
   - Emissions from vehicles, industries, and other sources release particulate matter (aerosols) into the atmosphere.
   - These particles can act as cloud condensation nuclei (CCN), around which water droplets can form.
   - Increased CCN can lead to changes in cloud properties and precipitation patterns. In some cases, it can enhance rainfall, while in others, it can suppress it depending on the nature and concentration of the particles.
3. Industrial Activities:
   - Industries emit various pollutants and aerosols that can influence cloud formation and precipitation.
   - Thermal emissions from industrial activities can also contribute to the UHI effect, further influencing local weather patterns.
4. Land Use Changes:
   - Urbanization replaces natural landscapes with impermeable surfaces
   - reduces the natural infiltration of water into the ground, leading to more runoff and potentially altering local hydrological cycles.
5. Vegetation and Green Spaces:
   - Reduction of vegetation and green spaces in urban areas reduces transpiration
   - This can impact local humidity levels and, subsequently, precipitation patterns.
   - Conversely, increasing urban greenery and parks can enhance local humidity through transpiration and potentially influence precipitation.
6. Climate Change:
   - Rising global temperatures alter the water cycle, leading to changes in precipitation patterns.
   - In London, climate change can lead to more intense and unpredictable weather events, including variations in precipitation such as increased frequency of heavy rainfall events.
7. Construction and Infrastructure:
   - Construction activities release dust and particulate matter into the atmosphere, which can influence cloud formation and precipitation.
8. Heat Emissions:
   - Heat emissions from buildings, vehicles, and other urban sources can contribute to the warming of the lower atmosphere.
   - This warming can influence local weather patterns, including precipitation.
   - Enhanced convection due to heat emissions can lead to the development of localized storm systems and increased rainfall

Question 10

What human activities effect winds in London?

Answer 10

1. Urban Heat Island Effect (UHI):
   - create temperature gradients between urban and rural areas.
   - can lead to localized wind patterns as air moves from cooler areas to warmer areas, resulting in increased urban breezes.
2. Building Design and Urban Planning:
   - Tall buildings and narrow streets can channel and redirect winds, creating wind tunnels and altering natural wind patterns.
3. Transportation:
   - The motion of cars, buses, and trains displaces air, creating micro-scale wind effects.
4. Industrial Activities:
   - Factories and industrial plants release hot air and gases into the atmosphere, which can create localized wind patterns due to the rising of warm air and the influx of cooler air to replace it.
   - Large industrial complexes can also act as physical barriers that modify wind flow around them.
5. Green Spaces and Vegetation:
   - Trees and vegetation can act as windbreaks, slowing down wind speeds and altering local wind patterns.
   - The reduction of green spaces due to urbanization can remove these natural wind moderators, leading to increased wind speeds in some areas.
6. Construction Activities:
   - can generate dust and debris that can be carried by the wind, affecting local air quality and potentially altering wind patterns.
   - The presence of cranes, scaffolding, and other construction structures can disrupt and redirect wind flow.