2.4 The human impact
What is the enhanced greenhouse effect?
A build up (increase in concentration) of certain greenhouse gases in the atmosphere as a result of human activity.
How does a change in the albedo cause global warming?
A change in the albedo affects the amount of solar energy absorbed at the Earth's surface. Deforestation and desertification means that dark forests are now lighter patches of land. These lighter patches of land reflect more sunlight - causes a cooling effect.
What is The Stern Review (2006)?
A report by Sir Nicholas Stern. It analysed the financial implications of climate change. The report said: - climate change is changing the planet - the risks of inaction are high - time is running out The effects of climate change vary with the degree of temperature change. Climate change causes a threat to the world economy - it will be cheaper to address the problem than to deal with the consequences. Doing nothing about climate change - the business-as-usual (BAU) approach - would lead to a reduction in global per person consumption of at least 5%. Global warming could deliver an economic blow of between 5 and 20% of GDP to world economies because of: - natural disasters - the creation of many climate refugees displaced by sea-level rise. Dealing with the problem will cost 1% of GDP (£184 billion).
Why has the amount of CFCs increased?
Aerosol propellants (old aerosols), solvents, refrigerants (refrigerators), foam-blowing agents release CFCs. CFCs are no longer used.
What is El Nino?
Also known as ENSO (El Nino Southern Oscillation). During El Nino the world is warmed by heat from the Pacific Ocean - it warms because the normal westward surface flow of ocean currents reverses and warm water moves east across the Pacific from Indonesia.
How is melting sea ice evidence for global warming?
Amount of arctic sea ice has decreased since late 1970s (when satellite observations began). - March maximum extent decreased by about 2.4% per decade since 1980 - it was at a record low in 2012 - it recovered in 2013 - it decreased to the third lowest June extent in the satellite record in 2015 Ice is becoming thinner. (But European Space Agency said it thickened by a third in 2013.) In June 2015 Antarctic sea ice reached its third highest June extent since satellite records began. - it has increased by over 4% per decade recently - it has been above the mean in 9 of the 13 years between 2001 and 2014, even though an active volcano is beneath it Scientists have found two channels that may be allowing warm ocean water to move beneath the 75-mile-long Totten Glacier - this would contribute to rising sea levels by melting ice. Between 2010 and 1014 the extent of Antarctic ice increased from 19 million square kilometres to more than 20 million square kilometres.
What are the positive effects of a changing climate in the UK?
An increase in timber yields (up to 25% by 2050), especially in the north (may be some decrease in the south). A northward shift of farming zones by 200-300km per 1C of warming, or 50-80km per decade, will improve some form of agriculture, especially pastoral farming in the north-west. Enhanced potential for tourism and recreation as a result of increased temperatures and reduced precipitation in the summer, especially in the south.
What are the five main factors that result in heat islands?
Anthropogenic heat Height and arrangement of buildings The nature of the building materials The presence of water Pollutants
Why has the amount of carbon dioxide increased?
Burning fossil fuels, especially coal Burning wood Deforestation, especially by burning - disruption of the rain forests About half of the CO2 produced is absorbed by natural sinks e.g. vegetation and plankton.
Where do greenhouse gases come from?
Carbon dioxide Human activities: - burning fossil fuels (coal, oil, natural gases) - deforestation (increases atmospheric CO2 levels and removes trees that convert CO2 into oxygen) Methane - cattle - natural wetland and paddy fields - bogs
What are the main points of the Stern Review?
Carbon emissions have increased global temperatures by more than 0.5C. The planet will warm by 2-3C within 50 years if the amount of greenhouse gases is not reduced. Temperature rise will transform the physical geography of the planet and they way we live.
How is ocean salinity evidence for global warming?
Drier areas and areas of high evaporation e.g. western Indian Ocean have become saltier. Wetter areas e.g. North Atlantic have fresher water. As the Arctic sea ice and glaciers melt and rainfall increases, more freshwater is entering the north Atlantic Ocean and diluting the salt water, making it less dense. This will cause it to remain on the surface and could prevent the sinking of north Atlantic surface water which power the Great Ocean Conveyor Belt. Tropical water will then no longer move towards the poles because there will be no sinking water to replace. These ocean currents show signs of weakening, which would make Europe colder.
How are biological indicators evidence for global warming?
Examples: - bee-eater (a tropical bird) is now found in the UK every spring - malaria (a tropical disease) is increasing in southern Europe where mosquitoes have moved in with the increased warmth - blanching of some coral reefs is a result from increased acidity of oceans
What are the socio-economic impacts of climate change?
Fishery section - rise in sea temperature causes fish species to move to colder waters - leads to a loss of revenue for tropical regions - global warming increases the frequency of storms - this effects fishing - it will be more dangerous to fish and there will be destruction of fishing equipment or flooding of fishing villages - marine species affected by climate change include plankton, corals, fish, polar bears, walruses, seals, sea lions, penguins, and seabirds - as water warms it holds less dissolved oxygen than cooler water. As a result, the world's oceans, coastal seas, estuaries, rivers and lakes are undergoing a process known as "deoxygenation." - around 2/3 of the countries most vulnerable to these risks are located in Africa - fishery sector could lose 50% of its jobs and US $311 million per year Tourism - climate directly affects tourism, especially on the coastline (temperature, rainfalls, strength of wind), aquatic parameters (surface temperature, invasive species, including algae and jellyfish) or coastal risks (erosion and risks) - beach areas could be closed off due to erosion and sea level rise - this will decrease the amount of tourism - effects economy in tourist businesses - attractiveness of the destinations will decrease Tourism - Maldives Sea level rise is likely to worsen environmental stresses in the Maldives e.g: - periodic flooding from storm surge - scarcity of freshwater for drinking and other purposes The white sand beaches and extensive coral reefs of the Maldives draw more than 600,000 tourists annually Maldives is projected to experience sea level rise on the order of 1.5 feet (half a meter)—and to lose some 77 percent of its land area—by around the year 2100. The country's two international airports - critical components of the tourism sector - lie within 165 feet (50 meters) of the coastline. Farming - African Farmers have developed a 98% rain-fed form of agriculture - climate change means droughts and floods are increasing so producing food in the expected quality and quantity will become problematic - increase in food prices will worsen food insecurity and more people will face malnutrition in LEDCs Health - heat stress, increase of diseases such as malaria or meningitis as well as illnesses caused by unclean water • Consequences from hunger and malnutrition • The development of toxic algae will impact the health of the ecosystem, with consequences on coastal productivity, nursery areas, biodiversity and human health through the consumption of contaminated. Coastal infrastructure and urban planning - coastal erosion and sea level rise, floods, water table pollution and habitat ad infrastructure deterioration. • The affects are mostly felt by vulnerable populations. • The economic cost associated with the potential impacts or risks of flooding is estimated at US $ 7 billion. • In Durban, South Africa where a result of the combination of high sea level and a cyclone, a swell over 14 metres surged up and created havoc estimated at US $ 100 million.
How is rising sea levels evidence for global warming?
Global sea level rose by an average of 3.1 mm a year between 1992 and 2010, twice the average rate for the last century. Record for highest yearly average height was 2014 - reached 67mm above the 1993 average. It is rising because: - melting glaciers send more water to the sea - thermal expansion - water expands as it warms Oceans store heat for longer periods than land and store it over a large body of water, so a small increase in temperature could cause a significant rise in sea level.
What are the political advantages of climate change?
Governments are now thinking of ways to save the world from climate change e.g. Democratic and Republicans. They are creating new policies that will help promote renewable energy globally e.g. solar and wind energy - also investing in further research about these new energy resources. Governments are now trying to limit the number of cash grants/loans (federal subsidies) to the fossil fuel industry.
What is the evidence for global warming?
Increase in global temperature Ocean salinity Melting sea ice Rising sea levels Melting glaciers Increasing acidity of the oceans Biological indicators of warming
What are the negative effects of a changing climate in the UK?
Increased storminess, flooding and erosion on natural and human resources - increased damage An increase in animal species, especially insects - due to northward migration from the continent. Small decrease in the number of plant species - due to the loss of northern and montane (mountain types). An increase in soil drought, soil erosion and the shrinkage of clay soils.
What are the social advantages of climate change?
Increased temperature and rainfall - prolong growing seasons of crops - could increase agricultural production and higher success rates of crop yields - more of the population will have access to food - reduces hunger. Winter deaths will reduce (e.g. influenza deaths as influenza peaks after cold seasons) - temperatures warm in colder regions. Warmer climates - safer conditions: - car accidents caused by wintering conditions kill 500 people annually in United States - many homeless people or lose who cannot afford to heat their homes freeze to death every year
What is La Nina?
It brings cooler years. Cold upwellings of water off the coast of Peru make: - the central and eastern part of the Pacific Ocean up to 2C cooler than average - eastern Australia have heavier than normal rainfall
How are winds in urban areas modified?
Lower speeds - urban areas have lower wind speeds than the surrounding suburbs - due to the roughness of the land surface - buildings at a variety of heights - helps increase surface friction Greater variability - on a smaller scale e.g. in CBD wind speeds are more variable - around some buildings winds are more gustly and strong - due to layout of buildings and building height - straight streets with tall buildings can produce urban canyons - these funnel wind down them which produce high velocities - turbulence is created by high-rise buildings disturbing the flow of air Large-scale convection
How is an increase in global temperature evidence for global warming?
Mean world temperatures rose overall between 1910 and 2014. Nine of the ten warmest years have occurred since 2000. Period of cooling from 1944 to 1975: - caused by an increase in particulates in the atmosphere - caused by increased pollution e.g. sulphate aerosols, soot, smoke - these condensation nuclei would cause denser clouds - means that more sunlight is reflected back to space Since the 1970s each decade has gotten warmer than the one before it - linked to the increase of greenhouse gases in the atmosphere. Increase between 1910 and 1940 was thought to be caused by mostly natural factors. Upper ocean heat has increased steadily over the past 20 years as a result of the oceans storing an estimated 63% of the heat added by enhanced global warming. Heat is accumulating in deep oceans rather than the atmosphere.
What are the atmospheric impacts of global warming?
Melting of arctic sea ice and loss of snow cover Reduce the albedo - results in less reflection of solar radiation and heating of the Earth and atmosphere - accelerates global warming. Warmer temperatures will lead to more evaporation from oceans Increases moisture in the atmosphere, giving the potential for increased cloud and rainfall in places, which would cause local cooling. Warmer temperatures in places with high atmospheric pressure will cause less rainfall and more severe droughts Warmer temperatures in places with high pressures e.g. South-west USA, South Africa, Australia and the Mediterranean, will cause less rainfall and more severe droughts. Heat waves will occur more, especially in cities This is because urban temperatures are always higher than those of surrounding rural areas. More frequent and more violent storms are expected This is because of greater moisture in the warmer air and more coastal flooding from storm surges are likely because of higher sea levels. No connection has been found between the number of tropical storms and warmer years. Warmer temperatures will result in the melting of permafrost in places such as western Siberia As the covering snow and ice melts, the darker rock and soil surfaces absorb more radiation. If all the permafrost melts, large quantities of methane will be released into the atmosphere - accelerates global warming. Methane releases from melting permafrost are causing wildfires in Alaska and Siberia. Permafrost store more than twice the amount of carbon that is in the atmosphere - this will be released as the permafrost decomposes - accelerates global warming.
What are the effects of a lack of moisture and humidity in urban areas?
More intense storms, particularly during hot summer evenings and nights - due to greater instability and stronger convection above built-up areas. Higher incidence of thunder - due to more heating and instability. Less snowfall - due to higher temperatures. Snow that does fall melts rapidly. Little energy is used for evapotranspiration - more energy is available to heat the atmosphere. People also produce heat in industry and by cars. Greater scattering of shorter-wave radiation by dust. Higher absorption of longer waves
How is melting glaciers evidence for global warming?
Most mountain glaciers have been shrinking since the middle of the 19th century. In 2013, three Norwegian glaciers were advancing and all glaciers in Nepal were either sable or growing because snowfall was greater than average in 2013. Glaciers and ice sheets in Greenland and West Antarctica are melting rapidly at the highest speeds since satellite records began and increasing sea levels. East Antarctic ice sheet is increasing.
What are the possible causes of global warming?
Natural causes - volcanic activity -El Nino - variations in solar output (sunspot activity) - changes in the amount of dust in the atmosphere (partly due to volcanic activity) - changes in the Earth's ocean currents because of continental drift Solar activity/orbital change (Milankovich cycles) - variations in the Earth's orbit around the Sun - variations in the tilt of the Earth's axis Human causes - industrial Activity - burning of fossil fuels & release of carbon dioxide - methane Production (agricultural production) - deforestation
What is El Nino and La Nina?
Natural events in the equatorial Pacific Ocean. Characterised by different pressure patterns and reversals of wind and ocean water movements.
Why has the amount of nitrous oxide increased?
Nitrate fertiliser Burning fossil fuels (especially diesel engines) Burning vegetation
How is increasing acidity of the oceans evidence for global warming?
Oceans have absorbed about 50% of the carbon dioxide emissions released by human activity by dissolving carbon dioxide into them, forming carbonic acid. Since 1750, the pH of the ocean surface has fallen by 0.1, from 8.2 to 8.1 - this is a logarithmic scale - this equals to a 26% increase in acidity. The 1750 level was calculated by: - analysing the CO2 content of air bubbles trapped in glaciers - knowing that the ocean surface has the same concentration of CO2 as the atmosphere. Ocean surface is less alkaline now.
Why has the amount of methane increased?
Rice production Cattle rearing Biomass burning Coal mining Ventilation of natural gas Fossil fuel combustion has also contributed through chemical reactions in the atmosphere - reduced the rate of removal of methane Bacteria in wet padi fields, bogs, waste landfill sites and the guts of cattle and sheep
Why is climate change a complex issue?
Scale - it includes the atmosphere, oceans and land masses across the world. Interactions between the atmosphere, oceans and land masses are complex. It includes natural and anthropogenic forces. There are feedback mechanisms involved. Many of the processes are long term and so the impact of changes many not have occurred yet.
What are the potential positives associated with climate change?
Social advantages Economic advantages Environmental advantages Political advantages
What are chlorofluorocarbons (CFCs)?
Synthetic chemicals that destroy ozone and absorb long-wave radiation.
What is the importance of the natural greenhouse effect?
The absorption and radiation of heat by the atmosphere is beneficial/essential for life on Earth - it makes the earth habitable. If there were no greenhouse effect, the Earth's average surface temperature would be -18°C (0°F) instead of 15°C (59°F).
What is the intensity of an urban heat island?
The maximum difference between the temperature of the rural area and the peak urban temperature. Intensity is low on hot summer days - both urban and rural areas are warm. Intensity is high at night - there is greater cooling in rural areas.
What is radiactive forcing?
The warming effect of a gas.
What is the climate like in urban areas?
They have a local and distinct set of climatic characteristics. This is because urban areas modify their climate on a small scale in several ways: - wind speeds - temperature - clouds and precipitation - pollution
What are temperatures like in urban heat islands?
They have many micro-climates - temperature is uneven: - sharper temperature change at the edge of the heat island - within the heat island their are peaks (linked with industry and city centre) and troughs (parks, reservoirs and rivers)
What are urban climates?
They occur as a result of extra sources of heat released from: - industry, commercial and residential buildings - vehicles - concrete - glass - bricks - tarmac These act differently from soil and vegetation. Some of these (dark bricks) absorb large quantities of heat and release them by night. The release of pollutants helps trap radiation in urban areas - urban micro-climates are different from rural ones: - greater amount of dust - increases concentration of hygroscopic particles - less water vapour - more carbon dioxide - higher proportions of noxious fumes - discharge of waste gases by industry is increased Urban heat budgets are different from rural ones: - in urban areas brick, concrete and stone have high heat capacities (absorbs more solar energy - major source of heat) - an urban area contains a greater surface area than a countryside - greater number of surfaces in urban areas allow a greater area to be heated - more heat-retaining materials with lower albedo and better radiation-absorbing properties in urban areas than in rural ones
How are temperatures in urban areas modified?
Urban areas are warmer than rural surroundings - known as the urban heat island Urban heat islands are on average 1-2C warmer per year than its surrounding rural areas e.g. Melbourne's average heat island is 1.13C. Increase in temperature effects: - air movement - pollution - humidity
What are the greenhouse gases?
Water vapour Carbon dioxide Methane Ozone Nitrous oxides chlorofluorcarbons (CFCs) They allow short-wave radiation from the Sun to pass through them, but the trap outgoing long-wave radiation - this raises the temperature of the lower atmosphere.
What factors influence the intensity of urban heat islands?
Weather conditions High-pressure systems with clear nights and still, sunny days - increase intensity. Intensity varies seasonally - high-pressure systems in winter bring cold weather to places e.g. Moscow and Montreal - this means people use more central heating which helps to increase any urban heat island effect. - winter months bring wetter, windier weather - the warmer air in the canopy layer in between buildings is flushed out by the colder air which is the same temperature as the rural air - this means average winter urban heat islands intensities are less Example: Melbourne's seasonal urban heat island shows this temperature pattern - summer mean of 1.29C and winter mean 0.98C
When is the temperature of the earth in equilibrium?
When the amount of water vapour and carbon dioxide stays the same and the amount of solar radiation stays the same. Human activities are disrupting the natural balance by increasing the amount of CO2 and other greenhouse gases in the atmosphere.
What is the natural greenhouse effect?
When the earth absorbs solar radiation/energy it heat up. As the rocks, air, seas warm, they radiate "heat" energy (thermal infrared radiation). From the surface, this energy travels into the atmosphere where much of it is absorbed by water vapor and long-lived greenhouse gases such as carbon dioxide and methane. When they absorb the energy radiating from Earth's surface, microscopic water or greenhouse gas molecules turn into tiny heaters— like the bricks in a fireplace, they radiate heat even after the fire goes out. They radiate in all directions. The energy that radiates back toward Earth heats both the lower atmosphere and the surface, enhancing the heating they get from direct sunlight. https://www.youtube.com/watch?v=ZzCA60WnoMk
What is the definition of anthropogenic?
(environmental pollution and pollutants) originating in human activity.
Why do urban areas lack moisture?
- a lack of vegetation - a high drainage density (sewers and drains), which removes water This means there are decreases in relative humidity in inner cities because of: - a lack of available moisture - higher temperatures
