Topic 2

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sarina

Cards (43)

how has the earth's climate changed over geological time ?
in the past 650 000 years, temperatures and carbon dioxide levels in the atmosphere have increased and decreased in a cyclical pattern, this is also known as the natural variability of the earth's climate
how do scientists determine the past climates of the earth ?
by analysing sediments from the seafloor and oxygen isotopes
higher concentrations of oxygen- 16 showing the earth's climate is warmer
higher concentration of oxygen- 18 shows the earth's climate is cooler
how has the earth's climate zones changed ?
the earth's climate zones have expanded and contracted over time
temperature is used to determine if the boundaries of climate zones have changed
what are the natural causes of climate variability over time ?
changes in the earth's orbit and angle of tilt
occurrence of sunspots
large- scale volcanic eruptions
how does changes in the earth's orbit cause climate variability ?
the earth's orbit stretches from circular to an elliptical shape and back again every 100,000 years
when the earth's orbit is the most elliptic, the earth will travel in a more oval shape, and more radiation reaches earth at the planet's closest approach to the sun than it does at the farthest departure from the sun
how does changes in the earth's angle of tilt cause climate variability ?
The earth’s axis varies back and forth between 21.5 degrees and 24.5 degrees every 41000 years
The greater the earth’s axial tilt angle (24.5 degrees), the more extreme our seasons are, like colder winters and hotter summers.
This is because at a 24.5 degrees tilt, each hemisphere receives more solar radiation during its summer, when the hemisphere is tilted toward the Sun, and less radiation during winter, when it is tilted away from the sun.
how does sunspot occurrences cause climate variability ?
higher sunspot activity is linked to higher amounts of solar radiation emitted from the sun
sunspots have lower temperatures, causing the areas surrounding the sunspots to radiate more energy, leading to more solar radiation emitted from the sun, resulting in higher temperatures on the earth
generally, periods of maximum sunspot activity correspond to periods of high annual surface temperatures on the earth
the number of sunspots rises and falls in a cycle of about every 11 years
how does large- scale volcanic eruptions cause climate variability ?
global temperatures decrease after a large volcanic eruption
a volcanic eruption releases large volumes of carbon dioxide, water vapour, sulfur dioxide, dust and ash spread around the lower atmosphere area of the earth
these particles absorb and reflect solar energy back into space
this temporarily offsets the greenhouse effect, lowering temperatures, until these particles grow large enough and fall down to the earth
what is an example of a volcanic eruption leading to lower global temperatures ?
the volcanic eruption of mount pinatubo in 1991 led to a drop in average global temperature of about 0.6 degrees over 15 months after the eruption
how has the earth's climate changed in the past 200 years ?
earth's climate changes are due to anthropogenic and natural factors
however, over the last 30 years, anthropogenic activities have produces more than 100 times more carbon dioxide than natural causes due to the growth in population and modern industrialisation, increasing greenhouse gases such as carbon dioxide, methane and nitrous oxide in the atmosphere
what are some anthropogenic causes of climate changes ?
burning of fossil fuels
changing land use for agriculture, industries and urbanisation
what is the greenhouse effect ?
it is the natural process where the greenhouse gases in the earth's atmosphere trap longwave radiation emitted from the earth's surface
describe how the greenhouse effect works
incoming solar radiation travels to the earth in the form of shortwave radiation
most of it reaches the earth's surface and is absorbed, warming the surface
the remaining radiation is absorbed or reflected by clouds in the atmosphere
the earth's surface emits longwave radiation
greenhouse gases in the atmosphere absorb and re-emit the longwave radiation which warms the earth
what is the enhanced greenhouse effect ?
it is when there is an increased greenhouse gases concentration due to human activities, causing less heat to be able to escape into space, and more heat is radiated back towards the earth's surface
what causes the enhanced greenhouse effect ?
due to the increased anthropogenic activities since 1850, hence increasing the concentration of atmospheric greenhouse gases
how does burning fossil fuels lead to the enhanced greenhouse effect ?

fossil fuels have high carbon content
the burning of fossil fuels like coal, oil and natural gas produces large amounts of carbon dioxide and other greenhouse gases which contributes to the enhanced greenhouse effect
fossil fuels are burned to create energy for human activities such as agriculture, industries and urbanisation
eg. the use of fossil fuels increased steeply since the start of the industrial revolution in the 1880s, contributing to more than 35 billion tonnes of carbon dioxide emissions per year
how does deforestation lead to the enhanced greenhouse effect ?
changing land use involve larger scale deforestation which contributes to the enhanced greenhouse effect
the large scale removal of forests occur due to the need for resources (timber and wood) for industrialisation and land for urban development or agriculture
deforestation results in increased levels of carbon dioxide
eg. globally, tropical deforestation contributes to about 25 % of annual greenhouse gas emissions
how does deforestation result in increased levels of carbon dioxide ?
reduces the number of trees that absorb carbon dioxide through photosynthesis
during photosynthesis, trees store carbon, thus when trees are cut down or burned, the stored carbon is released back into the atmosphere as carbon dioxide
clearing of trees exposes the soil beneath to sunlight, which increases soil temperature and the rate of carbon oxidation
how does agriculture lead to the enhanced greenhouse effect ? 
as population grow, forests are cleared to make space for agriculture to meet the rising demand for food
it contributes to about 30 % of global greenhouse gas emissions due to
burning of fossil fuels to produce energy for farm machinery
nitrogen in chemical fertilisers converts to nitrous oxide
livestock rearing and natural decomposition processes release methane
eg. in paddy rice fields, decomposition is rapid due to the high amount of moisture in the soil, which contributes to 5- 20 % of total methane emissions
how does industries lead to the enhanced greenhouse effect ?
fossil fuels are burned to generate energy to run the machinery and other factory processes
industries contribute about 43 % of greenhouse gas emissions annually
how does urbanisation lead to the enhanced greenhouse effect ?
in cities, fossil fuels are burned to power the high concentration of vehicles as well as household activities such as heating, cooling and lighting
how does climate change impact natural systems ?
increase in atmospheric and ocean surface temperatures
changes in ocean circulations
change in precipitation on land
how does climate change cause increases in atmospheric and ocean surface temperatures ?
most of the heat trapped by greenhouse gases is absorbed by oceans
over the last century, the sea surfaced has warmed by slightly over 1 degree
however, this increase is uneven, with some parts of the oceans warming up faster and some parts of the oceans being cooler
how does climate change cause changes to ocean circulations ?
water in the oceans is constantly moving around the world
the large scale movement of water is known as the global ocean circulation
warm surface water moves from the equator to the poles due to winds
the water then cools, becomes denser and sinks
this cools water then spreads along the bottom of the ocean, forming cool substance flows
eventually, the cool water rises back towards the surface of the ocean
how does climate change cause changes to ocean circulations ?
climate change is expected to slow down the global ocean circulation
water at the surface gains heat due to rising atmospheric temperatures and becomes less dense
the sinking of water at the poles is thus reduced which slows down the flow of water
ocean current in the atlantic ocean has slowed by about 15 %
describe the movement of water in oceans
water in the oceans is constantly moving around the world and it's large scale movement is called global ocean circulation
warm surface water moves from the equator to the poles due to winds
the water then cools, becomes denser and sinks
this cools water then spreads along the bottom of the ocean, forming cool substance flows
eventually, the cool water rises back towards the surface of the ocean
what are the changes in precipitation on land ?
climate change is strengthening existing precipitation patterns
wet regions are expected to get wetter due to increased precipitation, occurrence of excessive rainfall are expected to increase
dry regions are expected to get drier due to decreased precipitation, occurrences of drought are expected to increase
how does climate change cause an increase in precipitation and occurrences of excessive rainfall ?
warmer air results in increased water vapour in the atmosphere, especially in areas where surface water like rivers and lakes, is present because
warmer air is able to hold more water vapour
of increased evaporation
hence, in these areas, precipitation and the occurrences of excessive rainfall are expected to increase
eg. the pole, parts of southeast asia, central africa
how does climate change cause a decrease in precipitation and occurrences of excessive rainfall ?
warmer atmospheric temperature increase evaporation, which reduces surface water and dries out soil and vegetation
the lack of moisture can reduce the occurrence of rain
in areas with dry climate, the dry season may therefore get even drier, resulting in droughts
droughts are more likely to occur in places which are already experiencing dry climates such as the subtropics, where most of the world's deserts are located and mid- latitudes
eg. southwest USA
what are the impacts of climate change on aquatic ecosystems ?
threats to coral reefs
ocean acidification
disruption of marine food webs
how is climate change a threat to coral reefs ?
corals have a symbiotic relationship with algae that live in them
these algae are their primary food source and gives them their colour
due to increased ocean temperatures, the algae that lives in the corals leave them
hence, the corals lose its major source of food, turning white and are vulnerable to diseases which may lead to death
coral reefs are expected to decline by up to 90 % if oceans increase by 1.5 degrees
coral reefs are home to millions of aquatic species like fish, seahorses and sea turtles
what is an example of climate change being a threat to coral reefs ?
up to 2/3 of corals died in the northern section of the great barrier reef in australia in 2016 and 2017, species diversity hence decreased
how does climate change cause ocean acidification ?
oceans are important natural carbon sinks due to the presence of phytoplanktons which absorb carbon dioxide when they photosynthesise
increase in carbon dioxide emissions leads to oceans absorbing excessive amounts of carbon dioxide, leading to formation of carbonic acids in the water, making oceans acidic
since the industrial revolution in 1880s, ocean acidity has increased by 25 %
how does carbonic acids being present in oceans affect the aquatic ecosystem ?
carbonic acids dissolve calcium carbonate, which is needed by aquatic organisms such as corals, mussels and oysters to form their skeletons and shells
at current rates, coral reefs are eroding faster than new corals can form
as coral skeletons shrink, species that depend on them for food, habitat and shelter from predators are negatively affected and may potentially go extinct
eg. the average coral cover in the great barrier reef has dropped to about 30 % of what it was in the 1960s
how does climate change increase ocean temp. ?
ocean circulation transports heat from the tropics to the poles and allow for exchange of nutrients between surface and deep waters
the slowing down of ocean circulation reduces the sinking of water at the poles. warm surface waters mix less with cooler deeper waters
separating the near- surface aquatic life such as phytoplanktons from the nutrients below, causing a drop in phytoplanktons
species higher up in the food chain which feed on phytoplanktons like fish and whales, suffer from a lack of food, affecting the ecosystem and food webs
evidence that phytoplankton levels have decreased due to climate change
phytoplankton levels in the north atlantic have dropped by 10 % since the 1800s
in what ways can the increase in ocean surface temperatures disrupt marine food webs ?
changes in geographic distribution of aquatic species
changes in composition of aquatic ecosystems
how does climate change change the geographical distribution of aquatic species ?
due to warming oceans, aquatic species migrate to areas where temperatures are more favourable
aquatic species generally move polewards and into deeper, cooler waters
this causes
equatorial regions to experience a decrease in biodiversity
poleward regions will experience an increase in biodiversity
eg. tropical species like parrotfish and rabbit fish have migrated polewards
how does climate change affect the composition of aquatic ecosystems ?
as the geographical distribution of species change, the mix of prey, predators and competitions in the ecosystems also change, disrupting existing food webs and changing aquatic ecosystems
species that are unable to to migrate like corals, or move fast enough may not be able to adapt to higher sea temperatures
they may face local or global extinction as their environment becomes unsuitable for them, causing habitats and food sources to disappear
explain how the disruption of food webs can affect aquatic ecosystems    
some species
will flourish and others will not
might find an abundance of suitable food sources, causing population increase
might not find suitable sources of food, causing population decrease
tropical fish such as parrotfish and rabbit fish have migrated to cooler waters in japan and Australia.
these species feed on kelp in these cooler waters, causing a decline in kelp which affects other species, like lobsters and abalone in southern japan, that depend on kelp for food and protection from predators