Chapter 4 - Climate Change

The period that stretches from 2.6 million years ago to present day

A cenozoic era, the quaternary period marks a time when there was a global drop in temperature and the most recent ice age began

The period is split into 2 epochs the Pleistocene epoch and the Holocene epoch

The quaternary period is often called the ice age due to presence of a permanent ice sheet on Antarctica

During the Pleistocene epoch there were cold glacial episodes lasting approximately 100,000 years, thick ice would expand and retreat. Each glacial episode was followed by a warmer interglacial episode - warmer intervals 10,000 years

Began when the last glacial expansion ended and the current interglacial episode started - what we live in today

Still sheets of ice covering Greenland and Antarctica but our climate has remained relatively stable

Long term Change in the weather

Global climate change occurs very slowly over thousands of years. The earths average surface air temperature has increased by approximately 1 C in last 100 years

Have risen by 19 CM since 1900 and are expected to continue to rise - due to thermal expansion and ice sheets melting

They are the warmest they have been since 1850 and the worlds glaciers and ice sheets are decreasing in size

NASA data show since 2002 the volume of ice lost in Antarctica is 134 billion tonnes per year and 287 billion tonnes per year in Greenland

Natural recorders such as tree rings, fossil pollen, ice cores and ocean sediment

They estimate what the climate was like but are not as reliable Becuase these only indicate climate change rather than providing direct evidence of accurate temps

Long term climate change

Antarctic ice cores are used

They act like time capsules, they can be drilled - the deeper the snow is drilled the older the snow

Records go back about 800,000 years ago

Oxygen isotopes in ice cores are commonly used to estimate what the temperatures would have been

There are 3 different oxygen isotopes, the ratio of 2 types of Isotopes are measured to work out what the climate was like

Also when the ice cores are melted, trapped carbon dioxide and methane are released which can be compared to present levels the see the differences between climate then and now

The deeper the sediment the older the sediment,

Organisms and remains of plankton in the sediment reveal information such as past surface water temps and levels of oxygen and oxygen isotopes found

In a groan showing ratio of oxygen isotopes it shows the spikes to represent interglacials (Warmer times with less ice) and troughs show glacials (colder times with more ice)

Warmer times with less ice

Colder times with more ice

The solar output is measured by observing sunspots - the output has increased slightly from 1900-1940 and satellites have recorded intensity using radio meters since 1978

But solar output in last 50 years has barely changed even decreased so it can’t be responsible

The earths elliptical orbit changes every 100,000 years so distance changed so earth is closer and so warmer

Earth is also tilted on an axis and this angle changes due to gravitational pull of the moon so when tilt increases summers can get warmer and winters colder. The angle of tilt moves back and forth every 41,000 years

Earths not a perfect sphere so as earth spins it wobbles on its axis in a 20,000 year cycle

Orbital changes vary distribution of Suns energy

Scientists suggest these changes would not cause an ice age for at least 30,000 years

Volcanic eruptions temporarily cause is - sulphur dioxide is released which mixes with water vapour and Becomes a volcanic aerosol (sulphate) they reflect sunlight and reduce heat entering earth

Carbon dioxide also erupts to trap Suns heat but instead temperature drops as the cooling effect of the sulphate aerosols is usually greater

Naturally occurring phenomenon to keep earth warm enough for life - without it earth would be 33 C colder

Suns infrared Ray’s enter atmosphere and the heat is reflected by earths surface and natural layer of greenhouse gases allows some heat not to be reflected but some is trapped to keep earth warm

Where human activity have increased the layer of greenhouse gases which naturally exist

Less heat escapes from the earth and more is trapped so earth warms more

Burning fossil fuels

Agriculture

Transport

Heating

Deforestation

The rising levels of carbon dioxide form humans

Despite volcanoes releasing carbon dioxide - humans produce more than 130 time the volume

Greenhouse gases are 77% carbon dioxide and 14% methane and although it’s mainly carbon dioxide 8% nitrous oxide, methane molecules have 25 times and nitrous oxide has 125 times the global warming potential over 100 years when compared to carbon dioxide

Account for over 50% if greenhouse gas emissions

Release carbon dioxide into the atmosphere

Using in transportation, building, heating homes and the manufacturing industry, burnt in power stations to produce electricity

Contributes to 20% if greenhouse gas emissions

Produce a lot of methane from cattle during digestion and microbes as they decay organic material under water or flooded rice paddy fields produce it

As more population increases more food needed so more agriculture so more emissions in future

Clearing land for agriculture so farmers have space for livestock and crops

Logging for wood and paper products

Building roads to access remote areas

Making room for expansion of urban areas

During photosynthesis trees absorb carbon dioxide to reduce amount in atmosphere. Deforestation leaves trees fewer trees to absorb carbon dioxide and when trees are brunt to clear and area - with slash and burn the carbon dioxide stored by trees is released

From heavy rain, estimated damage from flooding could rise from £2.1 billion to £12 billion in late 2080s

Likely to increase and the risk of skin cancer and heat strokes, milder winters might lead to a decline in winter related deaths

Like health in Europe - heat waves can increase deaths but deaths from colder weather can decrease

Expected to increase but more irrigation required

Droughts will put pressure on food and water supplies due to hair he temps and less rainfall

A decrease in wheat and maize and small increase in rise

Fishing would decline affecting 40 million people

Reduced water flow and sea level rising changing the quailty of the water

Polar bears and seals will disappear with loss of habitat as ice melts

Deal with the cause of the problem - reduce or prevent the greenhouse gases which cause climate change and protect carbon sinks such as forests and oceans

Could also manage climate change through adaption

Such as wind, solar, geothermal, wave and tidal and biomass

Offer a solution to reduce the volume of greenhouse gases contributing to climate change

They are more expensive than fossil fuels but are becoming cheaper and more competitive - especially as they don't produce carbon dioxide

When light shines in solar panels it creates an electrical field - the stronger the sunshine on panels, the more electricity produced - typical homes save over a tonne of carbon dioxide a year as there are no greenhouse gas emissions

When there is no sunshine such as night solar energy can't be relied on to generate electricity

Earth naturally stores carbon dioxide underground in rock formations and in oceans but technology can replicate it

Carbon capture and storage (CCS) Can be used using existing power plants

Works by capturing carbon dioxide from emission sources and safely storing it, CCS can also remove carbon dioxide from the open atmosphere by converting it into supercritical carbon dioxide which is injected into impermeable rock and prevents it from leaving

CCS is expensive and unclear if carbon dioxide would remain trapped in long term

Doesn't promote renewable energy which prevents carbon dioxide emissions in first place

Investing in reforestation and a $40 billion investment in jt each year from 2010-2050 could increase carbon storage by 28%

Making an agreement to manage climate change, some countries can afford to mitigate climate change more than others and some are considered more responsible for causing climate change than others

Eg agree to reduce global emissions

Responds to the impacts of climate change and tries to make population less vulnerable

Strategies are local rather than global

If mitigation stopped all carbon emissions - adaption would still be required to manage climate change that are naturally occurring

Moving production to another location due to changing temps and extreme weather

Increasing irrigation in areas due to changing precipitation

Changing crops and varieties grown and the time of year they are planted such as drought resistant crops or switching to livestock production which tends to have more guaranteed returns

More difficult for poorer farmers

Summers will get drier and winters will get wetter

Reduce demand to save water eg offering retrofit packages of water efficiency devices

Eg Thames water opened a desalination plant to increase water supply - water taken from river at low tide when it's least salty

Reverse osmosis produces drinking water that requires a lot of energy so carbon emissions need to be offset by biodiesel electricity plant

Having a barrier eg the Thames barrier to prevent storm surges

Using costal management