Changing Climate – GCSE Revision guide How has Earth’s climate changed over the last 2.6 million years? The quaternary period is a period of time that we are currently living in. It began 2.6 million years ago. Quaternary period is an ice age Temperatures have always fluctuated. Colder periods are called glacials and warmer periods are called interglacials. We are currently living in an interglacial The Quaternary Period is divided into two epochs: the Pleistocene (2.588 million years ago to 11.7 thousand years ago) and the Holocene (11.7 thousand years ago to today). Although the quaternary period is an ice age, the temperature has always fluctuated, moving up and down, sometimes warmer and sometimes colder than it is today. The colder periods normally last about 100,000 years and are called glacial periods. The warmer periods normally last about 10,000 years and are called interglacial periods.
Transcript
Changing Climate – GCSE Revision guide
How has Earth’s climate changed over the last 2.6 million years? The quaternary period is a period of time that we are currently living in. It began 2.6 million years
ago.
Quaternary period is an ice
age
Temperatures have always
fluctuated.
Colder periods are called
glacials and warmer periods are
called interglacials.
We are currently living in an
interglacial
The Quaternary Period is
divided into two epochs: the
Pleistocene (2.588 million years
ago to 11.7 thousand years ago)
and the Holocene (11.7
thousand years ago to today).
Although the quaternary period
is an ice age, the temperature
has always fluctuated, moving
up and down, sometimes
warmer and sometimes colder
than it is today. The colder
periods normally last about 100,000 years and are called glacial periods. The warmer periods
normally last about 10,000 years and are called interglacial periods.
Changing Climate – GCSE Revision guide
Scientists believe since 1880
human activities (driving cars,
factories, agriculture, and air
travel) have resulted in a
significant artificial rise in
temperature.
Evidence for climate change Antarctica gives us a record of the atmosphere from 800000 years ago.
Gas trapped in the ice can be measured to estimate what the climate was like
thousands of years ago.
Lots of 16O and Earth was colder whereas lots of 18O and Earth was warmer.
Carbon Dioxide in the bubbles is another good indicator. The more CO2 the
warmer the climate. This indicator shows that Earth’s current temperature is
high compared to the past.
The expanse of sea ice in the Arctic is further evidence that our climate is
changing. We have been able to measure the sea ice minimum and maximum
since 1979 using satellite photos. On average the area covered by sea ice in the
Arctic has become smaller by 13.3% every ten years since 1979.
Global temperature data has been recorded by more than a 1000 weather
stations since 1880. Maps from different years can be compares to see how
climate has changed.
Geological fossil evidence
Plants and animals are good indicators of the environment as different species tend to
favour particular climatic conditions. Evidence of past climates can be suggested by the
presence of living organisms preserved as fossils. For example, the discovery of 60-
million-year-old crocodiles in North Dakota, USA, suggests that the climate of the past
was much warmer than it is today.
Elephant-like mammals called mastodons were widespread across the USA during cold,
glacial periods. Their thick woolly coats enabled them to survive the very cold
conditions. Fossil mastodons have been found from Alaska to Florida, indicating that
these cold periods extended across the whole of the USA.
Ice cores Ice cores extracted from the Antarctic and Greenland ice sheets have proved to be an
important source of information about past global temperatures. When snow falls in
cold polar environments it gradually builds up layer upon layer, year upon year. The
buried layers of snow are compressed and gradually turn to ice. The Antarctic ice sheet
is nearly 5 km thick in places and the oldest ice – at its base – is thought to be 800,000
years old.
Changing Climate – GCSE Revision guide Scientists are able to drill deep into the ice to extract cylindrical cores from ice that is
many thousands of years old. The layers of ice within a core can be dated accurately. By
analysing the trapped water molecules, scientists can calculate the temperature of the
atmosphere when the snow fell.
This information about accurate dates and temperatures has enabled scientists to
create graphs of temperature changes over the last 400,000 years. The results of this
research show the fluctuating temperatures that indicate past glacial and inter-glacial
periods
Ocean sediments
In the same way that layers of snow build up over thousands of years in a cold
environment, layers of sediment do much the same thing in deep ocean basins.
Scientists have been able to drill into sediments that are over 5 million years old.
By studying oxygen isotopes trapped within these sediments, it has been possible to
calculate past atmospheric temperatures.
Historical records
Historical records can provide additional evidence of climate change.
● Ancient cave paintings of animals in France and Spain depict nature as it was between
40,000 and 11,000 years ago, a period of time when the climate changed significantly.
The problem with cave paintings is dating accurately when they were drawn.
● Records of extreme weather events such as floods and droughts have been used to
suggest that in recent decades extreme weather events have become more frequent.
● Some studies have suggested that the timing of natural seasonal activities, such as
tree flowering and bird migration, is advancing. (The study of natural cycles like these is
called phenology.) A study of bird nesting conducted by the British Trust for Ornithology
in the mid-1990s discovered that 65 species nested an average of 9 days earlier than
they had in the 1970s. Swallows are arriving in the UK some 20 days earlier than they
did in the 1970s. Could this be evidence of a warming world?
● Diaries and written observations can also provide evidence of climate change,
although personal accounts can lack objective accuracy.
Changing Climate – GCSE Revision guide Global temperature data
Look at the image. It shows temperature
anomalies (variations from the long-term
average) for the period 2008–12.
This map was produced by NASA (National
Aeronautics and Space Administration)
using data collected from over 1000
ground weather stations together with
satellite information.
If you study the colour key, you should notice that there is a warming trend for most of
the world. This is consistent with earlier maps produced over several decades. NASA
suggests that average global temperatures have increased by 0.6°C since 1950 and
0.85°C since 1880.
Weather stations are not evenly distributed across the world and some regions,
especially in Africa, have a fairly sparse network. Computer programmes have been
used to produce global maps like this but this does not make them absolutely accurate
and reliable.
Shrinking ice sheets and glaciers
One of the most striking effects of the recent warming trend has been the retreat of ice
sheets and glaciers. Maps and photos show that many of the world’s glaciers are
retreating.
There is plenty of evidence from around the world of melting ice.
● The snows of Kilimanjaro have melted by 80 per cent since 1912.
● Glaciers in parts of the Himalayas could disappear by 2035.
● Arctic sea ice has declined in volume by 10 per cent in the last 30 years.
● Monitoring of the Greenland ice sheet by NASA suggests that it is shrinking.
● In 1910 Glacier National Park (USA) had about 150 glaciers; there are now fewer than
30.
● Low-level ski resorts in Europe have suffered economic hardship and some
businesses have had to close due to increasingly unreliable snowfall.
● The Muir Glacier (Alaska, USA) has retreated by 50 km in the last 120 years.
Retreat of the Columbia Glacier, Alaska, USA
The Columbia Glacier has its source in the Chugach Mountains in southern Alaska. It
flows for some 50 km to the sea in Prince William Sound. Its maximum thickness is 550
m. The glacier is known as a ‘tidewater glacier’ because it flows directly into the sea.
The Columbia Glacier is one of the most rapidly changing glaciers in the world. It has
been retreating at an alarming rate since the 1980s. Between 1982 and 2014, the snout
(front) of the glacier retreated by about 16 km and lost half of its thickness and volume.
In the early 2000s the glacier was retreating at a staggering rate of around 30m a day,
producing huge icebergs as the snout broke apart.
Changing Climate – GCSE Revision guide Scientists believe that the thinning of the ice may well be due to warming global
temperatures. If global warming continues, it is likely that the glacier will continue to
shrink. As it does so, the meltwater will contribute towards sea level rise.
The extremely fast rate of retreat at the snout may be due largely to mechanical factors
associated with the glacier extending into the sea, although global warming may well
have played a part in making the snout unstable in the 1980s.
Natural causes of climate change 1.) Milankovitch cycles.
Climate change is linked to the way the earth moves around the Sun and how it
wobbles and tilts as it does this.
Eccentricity – changes in the shape of Earth’s orbit.
Obliquity – changes in how Earth tilts on its axis.
Precession – the amount Earth wobbles on its axis.
Sun spots – Temporary and are caused by magnetic storms. They increase the amount
of energy Earth receives from the sun, causing it to warm up.
Volcanic eruptions – When volcanoes erupt they release huge amounts of dust
containing ash, sulphur dioxide, carbon dioxide and water vapour. The dust blocks out
the sunlight and contributes to a cooling effect.
Changing Climate – GCSE Revision guide
The natural greenhouse effect
The earth is kept warm and habitable because of
the natural greenhouse effect. Gases in the
atmosphere such as carbon dioxide and water
vapour are greenhouse gases. They trap some of
the sun’s radiation preventing it escaping to
space and therefore increasing the earth’s
temperature.
The enhanced greenhouse effect
Humans have put more greenhouse
gases into the atmosphere through
various activities. This makes the layer of
greenhouse gases thicker and traps even
more of the sun’s energy.
Changing Climate – GCSE Revision guide Sources of Greenhouse gases.
Carbon
Dioxide
Methane Halocarbons Nitrous Oxide
Contribution to
enhanced
greenhouse
effect.
60% 15% 15% 6%
Efficiency 25 times more
effective than
carbon
dioxide.
15000 times
more effective
than Carbon
Dioxide.
250 times
more efficient
that Carbon
Dioxide.
Source Burning fossil
fuels like coal
and gas to
make
electricity.
Industry, cars
and
deforestation.
Landfill sites,
rice production
and farm
animals.
Air
conditioning,
refrigerators,
aerosols and
foam
packaging.
Agricultural
fertilisers and
car exhausts.
Human causes of climate change There is a strong link between increases in Carbon Dioxide and increases in
temperature.
Changing Climate – GCSE Revision guide
Not all countries produce the same amount of Carbon Dioxide.
LIDC’s emit very low levels of CO2
AC’s and EDC’s emit much more.
China emits more than any other country – but don’t forget they also have the biggest
population in the world! Really you should examine CO2 per capita (per person) to get a
fair view.
Country share of total CO2 emissions in 2011
Changing Climate – GCSE Revision guide
CO2 emissions per capita
Changing Climate – GCSE Revision guide Global effects of climate change.
Effects of climate change on the UK Environmental Impacts
Climate
o Temperature will increase
o Winter rainfall may increase by 16% in parts of Western UK
o Summer rainfall may decrease by 23% in parts of southern England.
Extreme events
o Droughts are expected to be more frequent and intense, especially in
southern England.
o Flooding will become more common due to increased rainfall and sea
level rise.
Sea level rise
o By 12-76cm by 2095
o Loss of habitats, e.g. salt marsh
Wildlife
o Climate change will change the UK’s habitat. Some species have moved
North to areas with lower temperatures. This can upset the balance of
natural ecosystems and lead to species extinction.
Economic
Tourism
o Warmer weather could lead to more people staying at home for holidays
and boost the UK tourism industry.
o In other areas could lead to a decline, e.g. skiing in Scotland.
Agriculture
Social Economic Environmental
Reduced rainfall increases the risk
of wildfires which can destroy
people’s homes and put lives at
risk.
More extreme weather events
mean more money has to be spent
on predicting events (e.g. floods)
and reducing their impacts.
Temperatures expected to rise by 0.3-
4.8 °C between 2005 and 2100.
Some areas could become so hot
and dry they become impossible
to inhabit.
Areas of permafrost are melting
leading to the collapse of buildings
and pipelines.
Warmer temperatures are causing
glaciers to shrink and ice sheets like
Greenland to melt.
Some areas will struggle to supply
enough water due to problems
with water availability.
In farming some crops have
suffered from climate change
(maize crops have got smaller due
to warming). Some farmers in high
latitude countries are finding that
crops benefit from warmer
conditions.
Sea ice is also shrinking, leading to
loss of polar habitats.
Lower crop yields could increase
malnutrition, ill health and death
from starvation.
Water shortages affect ability to
make power through hydro-electric.
Coral reefs are suffering from
bleaching due to increasing sea water
temperatures.
Low lying coastal areas could be
lost to flooding as sea levels rise.
This could lead to migration and
overcrowding in other areas.
Precipitation patterns are changing –
warming is affecting how much rain
areas get.
Changing Climate – GCSE Revision guide o Warmer temperatures and longer growing season could improve
productivity of some crops.
o New crops (e.g. grapes) could be grown in Southern England. Perhaps
with increased need for irrigation and water storage schemes.
Fishing
o Fishing infrastructure (e.g. ports, boats) at risk from increasingly frequent
and more violent storms.
o Changing fish populations in UK waters could affect fishermen’s
livelihoods.
Social
Health
o Deaths from cold related illnesses may decrease but heat related illnesses will
put further strain on health services.
Water shortages
o Drier summers will affect water availability in areas that most need it e.g. South
East England where population density is increasing.
Floods
o Flooding may damage homes and businesses. Settlements on estuaries e.g.
Portsmouth, Cardiff and low lying areas near the coast (e.g. large areas of
