2.2 Consequences of climate change Flashcards
Predicted impacts on the physical environment can be modelled in a structured way by examining in turn possible consequences for which three spheres?
-The hydrosphere (the world’s water cycle and stores)
-The atmosphere (and the size of its carbon store)
-The biosphere (the world’s ecosystems, flora, and fauna)
What is the effect of climate change on the hydrosphere?
Major ice sheets have lost mass, land-based glaciers have shrunk and Arctic sea ice cover has fallen significantly since 1979.
What is the effect of climate change on the atmosphere?
-The atmosphere (and the size of its carbon store).
-According to the IPCC, by 2100, global temperature is ‘likely’ to have risen by more than 1.5°C relative to 1850 and may rise by more than 4°C.
-The IPCC is ‘virtually certain’ of further permafrost melting, which will release further methane into the atmosphere.
What is the effect of climate change on the biosphere?
-In 2016, sea temperatures in the northern section of the Australia’s Great Barrier Reef rose 2–3°C above the normal peak of about 30°C, due to the strong El Niño weather system and a continuing trend towards global warming.
-Two-thirds of corals in one part of the reef have died as a result of coral bleaching in overly warmer water.
Describe the interaction between the hydrosphere, atmosphere, and biosphere
-These interactions are complex and hard to predict.
-At the global level, the atmosphere, hydrosphere and biosphere can be considered to be an open system that forms part of a chain.
-Interlocking relationships among these three subsystems (such as the ocean’s ability to absorb carbon dioxide) are what make climate change complex and difficult to model.
Why is it that if all human GHG emissions (new carbon flows) were to be halted tomorrow, some degree of change would remain inevitable?
-Because up to 40 per cent of the anthropogenic carbon stock already in the atmosphere will remain there for more than 1,000 years.
-It is therefore ‘virtually certain’ that some level of warming will continue well beyond 2100.
Approximately ___ of all water on Earth is oceanic and saline.
97%
Other than the 97% of water that is oceanic and saline, where is most of the fresh water that makes up the remaining 3% located?
-It is locked up in land ice, glaciers and permafrost.
-This makes up the majority of the Earth’s cryosphere.
-Aside from cryospheric water, a relatively tiny amount of fresh water is stored in the form of groundwater, lakes, soil, wetlands, rivers, biomass and the atmosphere.
What are the five locations of water in the cryosphere?
-Sea ice (e.g. the Ross Ice Shelf)
-Ice caps (e.g. the Iceland ice cap)
-Ice sheets (e.g. the Greenland ice sheet)
-Alpine glaciers (e.g. Mer de Glace, France)
-Permafrost (e.g. the Alaska North Slope)
What does evidence suggest about the changes taking place in the cryosphere?
-That in general, becoming reduced in size.
-Patterns and trends are not uniform, however.
-In Antarctica, at altitudes above 400 meters, glaciers are not thinning and may even be gaining mass.
-This is because snowfall is increasing across the Antarctic Peninsula (because warmer air can hold more moisture).
-However, this increased snowfall in upper regions is not enough to offset melting at lower attitudes. Overall, across the whole Antarctic Peninsula, around four-fifths of all glaciers are receding.
What are the human implications of the loss of some or all ice stores?
-Rising sea-levels
-Threatened loss of water supplies in some heavily-populated regions of the world
What is the cryosphere?
Portions of Earth’s surface where water is in solid form.
Define mass balance
The difference between the amount of snowfall gained by a glacier or ice sheet, and the amount of ice lost through the processes of calving (blocks breaking off) and/or melting.
What are the changing characteristics of ice caps as cryosphere storage?
-Ice caps occur all over the world, from the polar regions to mountainous areas such as the Himalayas, the Rockies, the Andes, and the Southern Alps of New Zealand.
-The Furtwangler Glacier on Kilimanjaro is Africa’s only remaining ice cap. It is melting rapidly and may soon disappear.
What are the changing characteristics of alpine glaciers as cryosphere storage?
-Alpine glaciers are thick masses of ice found in deep valleys or in upland hollows.
-These glaciers are particularly important in the Himalayas where meltwater from 15,000 Himalayan glaciers supports perennial rivers such as the Indus, Ganges, and Brahmaputra.
-In turn, these are relied on by hundreds of millions of people in South Asian countries (Pakistan, Nepal, Bhutan, India, and Bangladesh).
-Glacial retreat is clearly evident in aerial photographs of retreating glacier snouts and vanishing ice, for instance at Wolverine Glacier in Alaska or Argentina’s Upsala Glacier. China’s Urumqi No. 1 glacier has reportedly lost more than 20 percent of its volume since 1962.
What are the changing characteristics of permafrost as cryosphere storage?
-The vast permafrost ring around the Arctic Ocean has already begun to thaw in places where temperatures have risen by several degrees since the 1960s.
-This melting is releasing large amounts of carbon dioxide and methane, potentially affecting the global climate further.
What are the changing characteristics of Greenland and Antarctic ice sheets as cryosphere storage?
-An ice sheet is a mass of glacial land ice extending more than 50,000 square kilometers.
-The two major ice sheets on Earth today cover most of Greenland and Antarctica.
-Together, they contain more than 99 percent of the freshwater ice on Earth (the Antarctic ice sheet covers the same area as the USA and Mexico combined; the Greenland ice sheet is much smaller).
-Overall, Antarctica is losing more ice than it gains each year.
-The deficit is around 70 gigatonnes per year (1 gigatonne is 1 billion tonnes).
-Warmer surface air temperatures around the northern Antarctic Peninsula are having a dramatic effect.
What do scientists estimate would happen if the Antarctic ice sheet melted?
-Sea levels would rise about 60 meters.
What are ice shelves and where do they mostly exist?
They are floating platforms of ice that form where ice sheets and glaciers move out into the oceans; they exist mostly in Antarctica and Greenland, as well as in the Arctic near Canada and Alaska.
What are the changing characteristics of Greenland and Antarctic ice shelves as cryosphere storage?
The Antarctic ice sheet is melting from below, as increased upwelling of relatively warm, deep water comes into contact with the underside of the ice shelves.
What are the changing characteristics of Arctic sea ice as cryosphere storage?
-Within the Arctic Circle lie northern parts of Russia, Canada, Alaska (USA), Greenland and Scandinavia, as well as the Arctic Ocean, parts of which remain covered with sea ice all year.
-Future temperature rises are projected to be greatest at high latitudes and in recent decades the Arctic has heated twice as fast as the rest of the world.
-Some experts predict the region will be entirely ice free by 2050.
-Temperatures 20 °C higher than usual in late 2016 suggest it may occur even sooner.
Describe the movement of carbon from one store to another
-Carbon moves naturally from one store (such as vegetation biomass) to another (the atmosphere) in a continuous cycle.
-The processes by which the carbon moves between these stores are known as transfers or fluxes.
-The recent increase in GMST has begun to affect the pattern of global carbon stores and fluxes.
Give some facts to show the importance of the ocean in the carbon cycle
-The oceans contain around 40,000 gigatonnes of carbon in the form of dissolved carbon dioxide, marine organisms and dissolved organic matter.
-It is estimated that about 30 per cent of the CO2 that has been released into the atmosphere has diffused into the ocean through direct chemical exchange. Dissolving carbon dioxide in the ocean creates carbonic acid.
-If this had not occurred then atmospheric concentrations of carbon dioxide would be even higher than they are.
What has been the effect of the increased acidity of the oceans?
It has harmful effects for coral reef organisms and other sensitive species.
How is the pattern of carbon that is stored in ice changing?
Permafrost ice melting releases methane gas (CH4), which is one part carbon and four parts hydrogen.
How is the pattern of carbon stored in ecosystems changing?
-The total amount of carbon stored in the terrestrial (land) biosphere has been estimated at just over 3,000 gigatonnes of carbon.
-The largest amount is held in tropical and temperate forests. In some places, canopies of tall broad-leaved trees – and their associated under-canopies and shrub layers – have a growing risk exposure to wild fires and so-called ‘megafires’ that are reportedly increasing in frequency.
-There will most likely be a 35 per cent increase in the days with high danger of fire across the world by 2050.
In which areas of the world is vegetation at the greatest risk due to climate change?
In the Eastern states of the USA, southeastern Australia, the Mediterranean and southern Africa is at greatest risk.
How have sea levels changed naturally in the past?
-Historically, sea levels have always been higher during warm periods and lower during cold phases.
-During the most recent Pleistocene Ice Age, the UK and France were joined together following a eustatic fall in sea level of around 100 metres (the English Channel was drained entirely of water).
Define eustatic
A worldwide change in average sea level resulting from a warming or cooling climate affecting the volume and/or depth of water in the oceans
What are the two reasons why a warmer climate results in deeper oceans?
-Melting of land-based glaciers and ice caps (and so increased runoff of water from the land to the sea)
-Thermal expansion of the oceans (water actually expands slightly in volume as its temperature rises, like liquid in a thermometer: in a warmer world the sea level would rise even if no ice had melted).
What are the different eustatic sea level rises that thermal expansion of the oceans and worldwide glacial melting are projected to bring?
-These combined processes are already giving rise to a total global average sea-level rise of approximately 3 millimetres per year.
-The IPCC projects a world sea-level rise of 260–820 millimetres by 2100, mostly due to thermal expansion.
-Significant glacier and permafrost meltwater runoff will produce another metre of sea-level rise by around 2200 (even if GHG emissions are cut significantly).
What will happen if no action is taken to cut GHG emissions?
Large-scale melting of the Greenland and Antarctica ice sheets could contribute 7-metre and 60-metre rises respectively (but this would take hundreds of years).
Diagram of a feedback loop showing why ice melting and sea-level rise might accelerate
What areas will suffer the worst consequences as a result of rising sea levels?
-Places that are coastal and low-lying, such as the Maldives islands.
-Other vulnerable places include estuaries or islands exposed to storm surges driven by cyclones, such as the Thames estuary and the Philippines.
-The places affected worst may be those suffering additionally from local sinking of the land.
-In these regions, the net effect will be an even greater rise in the level of water.
Give an example of a place that is being affected by rising sea levels
-The Ganges delta, in Bangladesh, is sinking by 10 millimetres a year as sediments settle.
-Some of the world’s poorest and most vulnerable people live here.
Why are the Marshall Islands threatened by rising sea levels?
Most of the Marshall Islands’ inhabitants live on islands barely 1 meter above sea level.
What is an extreme weather event?
-An occurrence such as drought or a storm which appears unusually severe or long lasting and whose magnitude lies at the extreme range of what has been recorded in the past.
-It is the occurrence of a value of a weather or climate variable (such as precipitation, wind strength or temperature) that is above or below a threshold value near to the previously observed maximum or minimum value.
Give some examples of scientific findings that show that while it cannot be said that a particular event was or was not caused by climate change, the scientists argue that they can explain how the odds of such events have changed in response to global warming (reword?)
-The devastating Texan heatwave that occurred in 2011 is now about 20 times more likely during La Niña years than it was in the 1960s.
-The UK’s exceptionally warm November 2011 temperatures are now about 60 times more likely to occur than they were in the 1960s.
Why do extreme weather events need looking at on a case-by-case basis?
-Natural variability will always bring periodic extreme floods, droughts and heatwaves to different places; it takes years of data to distinguish this from any underlying trend.
-For this reason, the precise link between various extreme weather events and climate change is still debated.
-However, there are highly logical reasons why we should expect some hydro-meteorological hazards to become more commonplace on account of a rising GMST.
Why do extreme weather events need looking at on a case-by-case basis?
-Natural variability will always bring periodic extreme floods, droughts and heatwaves to different places; it takes years of data to distinguish this from any underlying trend.
-For this reason, the precise link between various extreme weather events and climate change is still debated.
-However, there are highly logical reasons why we should expect some hydro-meteorological hazards to become more commonplace on account of a rising GMST.
What is the risk equation?
