Spec S4 Flashcards
(36 cards)
What is the importance of the carbon cycle?
- All living organisms depend on carbon, which is a fundamental building block of life
- Green plants and phytoplankton extract carbon from the atmosphere in the process of photosynthesis, they are primary producers in ecosystems, converting sunlight and CO2 to carbohydrates, which support all consumer organisms, including humans
- Carbon stores such as ocean sediments and carbonate rocks lock away carbon for millions of years, helping to maintain atmospheric CO2 at levels conducive to life on the planet
- Decomposition and oxidation ensure that CO2 is recycled rapidly, replenishing stores of CO2 in the atmosphere for photosynthesis
- CO2 and CH4 in the atmosphere are important GHGs, absorbing long-wave radiation from the Earth’s surface and contributing to the natural greenhouse effect
- The carbon cycle operates in a state of dynamic equilibrium, with carbon moving continuously between stores, over millions of years a balance exists between flows of carbon into and out of stores, but on shorter timescales the amount of carbon held in the atmosphere can vary
Examples of negative feedback
Expansion of forests
Increased Cloudiness
Increased aerosols in the atmosphere
Expansion of forests
Temperatures rise, tree line advances polewards, expansion of forests absorbs more CO2 from the atmosphere
Increased cloudiness
Higher temperatures, higher rates of evaporation and levels of atmospheric water vapour, increases cloud cover increases reflection of incoming solar radiation (albedo) back into space and lower temperatures
Increased aerosols in the atmosphere
Burning fossil fuels releases tiny airborne particles (aerosols) of smoke, dust and sulphur to the atmosphere, they reflect incoming solar radiation back into space which lowers global temperatures - known as global dimming
Examples of positive feedback
Increased evaporation
Reduced albedo
Declining forest cover
Increased cloudiness
Release of methane hydrates
Melting of permafrost
Increased ocean acidity
Increased evaporation
Global warming intensifies evaporation from ocean and land surfaces, atmospheric water vapour increases, raises global temperatures, further evaporation
Reduced albedo
Higher temperatures, melting of glaciers, sea ice and snow fields, reduces albedo, more solar radiation absorbed, temperatures increase, more melting
Declining forest cover
Higher temperatures, tropical forest trees become stressed and die, releases CO2 from biosphere, higher temperatures, threatens more forests
Increased cloudiness
Higher temperatures, increased evaporation, more water in atmosphere, increased cloud cover, help retain heat from Earth and contribute to further temp rise, more evaporation
Release of methane hydrates
Methane hydrates are locked away in ocean sediments, stability of this carbon store depends on temperature, as oceans warm there is potential for massive release of methane, a GHG 20x more potent than CO2
Melting of permafrost
CH4 and CO2 stored in vast quantities in permafrost, as temperatures rise this is melted and the GHGs are released, creating enhanced greenhouse effect, further warming and more melting
Increased ocean acidity
As oceans absorb more CO2, become more acidic, this reduces oceans’ capacity to absorb CO2, in long term this increases CO2 in atmosphere, contributes to greenhouse effect
Mean global temperature change
- All of IPCC projections for next 70-80 years show significant rises in mean global temperatures during the 21st century
- Depending on trajectory of GHG emissions, temperature increases range from 0.3 degrees to 4.8 degrees, however a mean global temperature rise of around 2 degrees is the most likely scenario
Mean global sea level changes
- Rising sea level is the result of thermal expansion of the oceans due to warning and the loss of ice by ice sheets and glaciers on land
- Ice losses are caused by surface melting and increased rates of glacier flow
- Sea level has been rising since the onset of industrialisation in the mid 19th century
- 1901-1990 = mean global sea level rose by 1.5mm/yr
- 1990-2010 = mean global sea level rose by 3.0mmyr
- IPCC forecasts indicate an even more rapid rise during the rest of the 21st century
- Forecasts depend on the future trend of GHG emissions, current projections suggest a minimum rise of 0.3m by end of the century, and maximum of 1m
- Most pessimistic forecast doesn’t;t include potential collapse of marine-based sections of West Antarctic ice sheet, could substantially increase the 1m figure
What impacts can climate change have on marine ecosystems?
- Global warming raises sea surface temperatures
CORAL REEFS - Coral reefs (one of most biodiverse and productive ecosystems on the planet) currently being threatened by bleaching, caused by higher SSTs
- Bleaching and death of corals are possible with only a small rise in water temperature (1-2 degrees), in the last 30 years Indonesia has lost half of its reefs to bleaching, in Caribbean the proportion has reached 80%
ARCTIC - Warming of Arctic Ocean, shrinking of sea ice, decimated ice algae, which are the base of the marine food chain
- Sea ice also cortical to the survival of marine mammals such as walrus and seals
- Walrus use the coastal sea ice as diving platforms for foraging on sea bed and travel long distances on floating ice, seals use sea ice to rest, give birth and raise pups
- Exposed on ice, they are hunted by polar bears, the disappearance of sea ice is the main reason for a projected two thirds decline in the polar bear population by mid-century
- Few human groups rely directly on natural ecosystems, exception is the indigenous Inuit hunters of the Arctic, whose economy and culture depend on hunting marine mammals, especially seals, walrus and whales
- Thinning and melting of the sea ice makes hunting hazardous, with more open water in the Arctic, the number of killer whales is increasing, as natural predators of narwhals and seals, killer whales are in direct competition with Inuit hunters
FOOD SUPPLY / FISHING - Around UK, average SSTs have risen by 1.6 degrees since 1980, warming seas limit food supplies, growth rates and spawning for many fish species
- Therefore, some indigenous cold water species (eg. cod, haddock) had moved northwards towards Iceland whilst warm water species such as sea bass have migrated into UK waters
- This movement impacts the UK fishing industry, not only will commercial fishing have to switch to new species but the fishing effort for cold-water fish like cod will have to shift northwards
What impacts can climate change have on terrestrial ecosystems?
- Temperatures are rising faster in the tundra than in any other ecosystem
HABITAT CHANGE - As permafrost thaws, wetland areas expand, attracts more migratory birds, influxes of spring migrants from the south will occur sooner, breeding season will last longer and higher temperatures will ensure an abundance of insects
- Southern fringes of the tundra will lose their open aspect as the tree line advances north, as forests replace the tundra, changes in habitat will affect indigenous plant and animal species
- Migration patterns across caribou (which spent summer on the tundra) will be disrupted, as open tundra habitats shrink, predators such as snowy owls and arctic foxes which rely on the lemming population will be forced upwards
- Cairngorms in north east Scotland supports the most extensive mountain tundra in the British Isles, several animal species such as arctic hares are restricted to this type of habitat, it is estimated that a 1 degree rise in temperature requires an uphill movement of 200-275m to maintain the same habitat, animals living at 600m would have to move to 800m - even with this small warming, Scotland would lose 90% of its arctic-alpine habitats, if warming continues these species would eventually run out of suitable habitat and face extinction
PHENOLOGY - Phenology is the study of changes in the timing of sprint and other natural seasonal events, it is in indicator of global warming
- According to the IPCC, in the past 30 years sprint has occurred earlier by 2.3-5.2 days per decade on average, this creates a loss of synchronisation between species, animals awaken from hibernation or start to breed before the emergence of food resources such as leaves or insects
What impacts can climate change have on human health?
- World Health Organisation forecasts an additional 250,000 deaths per year worldwide between 2030 and 2050 linked to climate change and the spread of infectious disease, malnutrition and diarrhoea
VECTOR-BORNE DISEASE - Climatic change stimulates transmission of vector-borne diseases and their geographic range, dengue fever, a disease spread by the Aedes mosquito and formerly confined to the tropics and sub-tropics, is today found in 28 US states
- Between 1995-2005, 4000 cases were reported, rising temperatures and increased rainfall have favoured the spread of mosquitos carrying the disease
- Climate change also responsible for spread of Lyme disease in the USA, the disease is transmitted by ticks, which thrive in warmer conditions - currently distribution is expanding northwards, it is likely that the disease carrying ticks will eventually colonise Canada
- Malaria leading cause of death in developing world, claims around 800,000 lives per year, the mosquitos that spread it thrive in warm, wet conditions, disease is seasonal throughout tropical Africa, in a warmer and wetter world, the disease could spread to malaria-free parts of the world including southern Europe and Mediterranean
FOOD POISONING - Higher temperatures increase risk of food contamination by salmonella and other bacteria which cause food poisoning
- Heavier rainfall increases flood frequencies and the probability for water supplies being polluted by human waste, bacteria in drinking water will multiply the risk of diarrhoea (already a major cause of death among children in LIDCs)
FOOD SECURITY - Health could be compromised by droughts and floods reducing crop yields and food production, which could threaten food security and human health with widespread malnutrition and under nutrition in LIDCs
- Global food supply has already been reduced by climate change and forecasts by the IPCC suggest significant reduction in staple cereal crops by 2030
What impacts can climate change have on weather?
EVIDENCE OF EXTREME WEATHER
- Rising temperatures are known to disrupt the middle latitude and sub-tropical jet streams, increase evaporation and humidity and modify pressure patterns both in the atmosphere and at the surface
- Since mid-1970s, the frequency, intensity and duration of extreme weather have increased, eg. the 2005 hurricane season in the North Atlantic Caribbean area produced a record-breaking number of storms, including five category 5 hurricanes and in August 2015, for the first time, three large hurricanes were active simultaneously in the Pacific
- Sahel region of Africa has endured numerous severe droids in the past 40 years, which have accelerated desertification, in 2015, California entered its fourth successive year of drought
IMPLICATIONS
- Heavier and more frequent rainfall events associated with depressions and thunderstorms will cause severe river floods, groundwater floods such as those that devastated the Somerset Levels in winter 2014 will become more common, possible responses: engineering to strengthen hard flood defences, managed land-use change in catchments to delay run-off and restrictions on housing and infrastructure on active floodplains
- More powerful tropical cyclone which generate huge storm surges threaten populations in low-lying coastal areas, Hurricane Katrina caused massive loss of life and economic damage in New Orleans and along the Gulf coast in August 2005
- More frequent and more powerful depressions will accelerate rates of coastal erosion in mid-latitudes, nations will have to choose between hard defences to give complete protection, coastal realignment which allows the coastline to retreat inland and form natural defences such as mudflats and salt marshes or non-intervention allowing erosion and disposition to establish a new equilibrium
- Heatwaves expected to occur with greater frequency in the future, posing a direct threat to human health especially to vulnerable groups like the elderly in urban areas where the heat island effect is most intense - an exceptional and prolonged heatwave struck much of Europe in summer 2003, beginning in June and continued until mid-August, causing an estimated 30,000 excess deaths, most of the victims were aged 75 or above, mitigating the health impact of heatwaves in future will include early warnings, informing vulnerable groups of the precautions they should take and greening urban areas to promote evaporation and cooling
What does the vulnerability of people to climate change depend on?
Where they live
Ability to cope
How does where people live impact their vulnerability to climate change?
FARMING
- Most rural communities in the developing world are subsistence farmers, the majority depend on direct rainfall for successful cultivation of crops and raising of livestock, however climate change will make rainfall more erratic and floods and droughts will become more frequent
- These problems will hit farmers hardest in marginal farming environments where rainfall is only sufficient enough to support agriculture
- Since 1970s, extensive areas of crop and grazing land in the Sahel in northern Africa have been abandoned due to severe land degradation and desertification, prolonged droughts linked to climate change have been extremely harmful
- Other farming regions likely to be affected by drier conditions in the future include prime agricultural areas such as Prairies in North America
GLACIERS
- 98% of world’s glaciers currently retreating, means that regions that rely on glacial meltwater for irrigation will almost certainly experience water shortages in future, some of the rural regions affected such as northern India and eastern China are among the most densely populated places in the world
FLOODING
- Populations in low-lying coastal regions in the tropics and sub-tropics are vulnerable to flooding caused by a combination of rising sea level and more powerful tropical storms
- Once again people in poorer countries are at most risk, storm surge in Bangladesh in 1991 killed 138,000 people, vs Hurricane Katrina (one of most powerful storms on record) in 2005 which killed just over 1400
- Storm surges not only cause loss of life but destroy crops and livestock, and leave over-stalinised soils and contaminated water supplies
ARCTIC
- Global warming is most rapid in the Arctic, where the thawing of permafrost and melting of sea ice threaten the livelihoods of native Inuit hunters
How does people’s capacity to cope impact their vulnerability to climate change?
- Inequality and poverty at a global scale mean those at greatest risk are concentrated in the world’s poorest countries, people living in poverty have fewest entitlements to protect themselves and their families against natural climatic hazards and to cope with losses of crops, property and steep rises in food prices
- The elderly, young and chronically ill are among those least able to cope with the effects of climate change, this is illustrated by the impact of heatwaves in densely populated urban areas
- Prolonged spells of extreme temperature like the heatwave that struck Europe in summer 2003 caused 35,000 deaths and the majority of them elderly people age 75 and over
Vulnerability of the environment to climate change
TUNDRA
- Rising temperatures melt permafrost, disrupts vegetation, creates extensive thaw lakes and wetlands, initiating mass movement
- Forests will invade the southern margins of the tundra
MOUNTAINS
- Glaciers will retreat in warmer conditions, thawing and glacier retreat will make slopes less stable and trigger more frequent mass movements
- The snow line will recede upslope and the winter snowpack will thin, these changes will reduce meltwater inputs to rivers
RAINFOREST
- Computer models predict that Amazon rainforest will become warmer and drier by mid 21st century
- As deforestation increases (partly due to climate change) the water cycle will weaken, creating positive feedback and accelerating forest loss - 30-60% of the Amazon rainforest rainforest could become dry savanna grassland by the end of the century
COASTS
- Higher sea levels and more powerful storms will increase rates of erosion on both upland and lowland coasts
- Shorelines will retreat inland, coastal environments at particular risk include dunes, salt marshes and mudflats
What are the key mitigation strategies used to cut global emissions of GHGs?
Energy efficiency and conservation
Fuel shifts and low carbon energy sources
Carbon capture and storage
Reforestation and forest conservation
