2.4 The Human Impact Flashcards
What is the enhanced greenhouse effect?
Greenhouse gases emitted as a result of human activity. There is a natural greenhouse effect essential for keeping our planet warm enough to be inhabitable however in recent years human activity has made it enhanced.
In short, the suns rays pass through the atmosphere as insolation without being absorbed or reflected back to space. Long wave infra-red is then reradiated back out the Earth’s surface, and greenhouses gases retain this heat more, warming up the Earth’s atmosphere
What are some of the natural causes of the effect?
Changes in solar output, the shape of the Earth’s orbit, the tilt of the Earth’s axis, volcanic activity.
The Level of CO2 has risen from 313ppm to 400ppm since industrial times.
Temperatures have risen 0.7 degrees. The natural GHE causes temperatures to be 15.
What are the 4 GHGs?
Carbon dioxide: 313 to 400ppm since 1800s. Emissions account for 65% of CO2 release. It is linked to burning fossil fuels, deforestation, natural land use changes
Methane: sources from wetlands, marshes, swamps, rice farming, landfills of organic matter, burning vegetation, bowels of animals. It makes up 20% of GHGs and is 20 times more potent than CO2. Concentrations have increased by over 150%, mainly from BRICs countries
CFCS: Thousands of times more potent than CO2 and also break the ozone layer which protects the Earth from UV. It is sourced from fridges, air conditioners, aerosols, industrial solvents and cleaning agents. It is the first target to be removed
Nitrous oxides are released during burning of fossil fuels and biomass as well as from fertilizers and deforestation. It is a minor component and not very potent - is a natural part of the atmosphere.
What is some evidence for the enhanced greenhouse effect?
Measuring past climate within rocks, living organisms and their habitats, recent measurements.
They suggest we are warming faster due to GHGs. This happens anyways due to solar levels, volcanic eruptions, continental drifts and variations in the orbit however never to this scale.
What are some of the impacts of the EGE?
Intense storms have become more common due to more evaporation, floods, landslides and destructive storms. This has caused hurricanes in Myanmar, killing tens of thousands.
Hurricanes: warmer oceans provide more energy, making storms more powerful. Katrina was the most destructive storm in US history, taking 2000 lives and 300000 homes, costing over $100bn.
Persistent heat waves cause droughts, crops wilting, animal deaths, disease
global temperatures: rapid increase, upper ocean heat increased steadily. Estimated 60% of added heat is stored in the ocean.
Ocean salinity: Dry areas with high evaporation become saltier and wetter areas are fresher. This is because glaciers are melting, causing more freshwater to enter the oceans and dilute the saltwater. This could make water much less dense and affect the Great Ocean Conveyor Belt
Melting sea ice: volume falling 2.4% per decade. Most glaciers shrinking since 1800s resulting in increased sea levels. Estimated the rise of sea levels are up to 3mm per year due to the thermal expansion as well as melting glaciers. This rise in sea level has put many low lying areas under threat.
Increasing acidity of the ocean: oceans absorbed about 50% of CO2 emissions, forming carbonic acid which has risen the pH from 8.2 to 8.1. This can kill wildlife.
What agreements are put in place to combat climate change?
The Paris agreement in 2015 for 174 to limit global warming
Kyoto protocol introduced to slow down emissions and put in fines and grants for firms.
How is wind affected in urban microclimates?
- Lower winds due to friction from land surfaces and buildings
- Grater variability as winds travel through difference spaces, around buildings, smaller gaps causing them to twist and expand creating turbulent airflows. When air reaches the face of a building, the pressure builds up flowing over the front of the building, causing a reverse circulation behind the building creating complicated turbulence.
- Large scale convection: the urban heat island effect causes large amounts of convection, leading to low air pressure and drawing in air from surrounding rural areas.
How is temperature effected in urban areas?
Warmer due to anthropogenic heat, buildings and building materials
Anthropogenic heat is released by human activity - vehicles, buildings, heating, industry.
Buildings can affect it as tall, dense buildings create natural insolation depending on the albedo of the surfaces. The buildings can reflect heat off many surfaces, each one absorbing some of the energy and warming up in the process.
The buildings also funnel in radiation, causing more heat on the ground and reduces the change for it to escape, as when it is re-emitted the chances are it will just be absorbed by another building.
The material changes the specific heat capacity. For instance, concrete has a low SHC and the surface is exposed so there is a larger surface area to store and release slowly overnight. Dark and dry tarmac heats surfaces as it absorbs heat, causing less latent heat transfer
How is water effected in urban areas?
Surplus heat is transmitted as latent or sensible heat, which evaporates water. The surplus heat will go into the water and be released when it condenses
How do pollutants affect urban microclimates?
Dust, aerosols and GHGs alter the amount of energy flowing in and out of an area. Smoky dusty cities can reduce the amount of sunshine in the city surface and cool the area. On the other hand, pollutant domes formed by GHGs can absorb heat and prevent it escape due tot he build up of GHGs and ozone
What is the weather like in urban microclimates?
The urban heat island effect causes convectional uplift as the land becomes hot. This intensifies storms and clouds. There is also greater condensation nuclei like dust which encourages cloud formation as the water vapour needs the surface to take place. Storm cells may also be ‘refuelled’ by the warmth of cities which can lead to enhanced rainfall
Urban microclimates are dirtier than rural areas which has reduced sunshine received up to 30%. It has also caused smog due to dirty air causing rapid chemical reactions, allowing pollutants to stagnate in the slow moving air. Smog mainly occurred in industrial times from coal factories and steam trains.
Temperature inversions were built up under high pressure, which trapped pollutants in the lower atmosphere, allowing water vapour to condense around them.
