Chapter 4 - Climate Change Flashcards
What’s the quaternary period
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
How was the climate in the Pleistocene 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
How was/is the climate in the Holocene epoch
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
What is climate change
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
How have sea levels changed?
Have risen by 19 CM since 1900 and are expected to continue to rise - due to thermal expansion and ice sheets melting
How have ocean temperatures changed
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
What’s proxy data
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
What do ice cores show
Long term climate change
Antarctic ice cores are used
How do we use ice cores
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
Tell me about using ocean sediments
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)
What’s an interglacial
Warmer times with less ice
What are glacials
Colder times with more ice
How does solar output suggest climate change is natural
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
How could orbital changes cause climate change
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
Tell me how volcanic activity could cause climate change
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
What’s the natural greenhouse effect
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
What’s the enhanced greenhouse effect
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
What activities can increase the greenhouse gases
Burning fossil fuels
Agriculture
Transport
Heating
Deforestation
What is likely the main cause of climate change
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
How do fossil fuels cause climate change
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
How does agriculture cause climate change
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
Why are forests deforested
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
How does deforestation cause climate change
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
Tell me the flood Risk effect in uk of climate change
From heavy rain, estimated damage from flooding could rise from £2.1 billion to £12 billion in late 2080s
