3.1.1.4 Climate Change Flashcards
What is climate change the result of?
climate change is the result of natural and human factors and has a range of effects
How old is the Earth believed to be?
The Earth is believed to be 4.55 billion years old and so studying the Earth has led us to devise a geological timescale that divides Earth’s history into a series of eras, periods and epochs
What is the quaternary period?
- The period of time that spans from 2.6 million years ago to the present day is called the Quaternary Period
- This period marks a time when there was a global drop in temperature and the most recent ice age began
- It is thought that there have been 5 ice ages in Earth’s history
What is the Holocene?
- The Holocene is the current geological epoch. It began approximately 11,650 calendar years before present, after the last glacial period, which concluded with the Holocene glacial retreat
- The Holocene and the preceding Pleistocene together form the Quaternary period
What has the Holocene witnessed?
- Holocene has witnessed all of humanity’s recorded history and the rise and fall of all its civilisations
- Humanity has greatly influenced the Holocene environment; while all organisms influence their environments to some degree, few have ever changed the globe as much, or as fast, as our species is doing
How have global temperatures changed since 1800 and 1900?
- 1 degrees C since 1800 and about 0.7 degrees C during last 100 yrs
- since 197- rate of increase has been roughly 0.17 degrees C per decade
Evidence for climate change:
- rising sea levels
- shrinking glaciers and melting ice
- seasonal changes
- ice cores
- ocean sediments
By how much have the sea levels changed?
- according to IPCC (2019) global mean sea level is rising and acceleration
- on average between 1993 and 2015 global sea levels rose by 3.2mm per year compared with 1.4mm between 1901 and 1990
By how much have sea lives risen in the past 100 years?
Intergovernmental Panel on Climate Change (IPCC), the average global sea level has risen between 10 and 20 cm in the past 100 years
What are the 2 main reasons for sea levels rising?
- melting of freshwater glaciers and ice sheets, adding water to the oceans
- thermal expansion (increase in volume of seawater) cause by an increase in water temperature
How much ice have we been losing from Antarctica per year according to NASA data?
NASA data shows that since 2002 we have been losing an average of 134bn tonnes of ice from Antarctica each year
By when may glaciers have completely disappeared?
Glaciers may have completely disappeared by 2035
What is the % reduction in Arctic sea ice since 1975?
65 % reduction in Arctic Sea ice since the 1975
How have the timing of natural seasonal events been changing?
studies suggest that the timing of natural seasonal activities such as tree flowing and bird migration is advancing by up to 2 days per decade
How has bird nesting changed in Finland?
- a study in Finland (from 1975 to 2012) discovered that birds are nesting earlier, increasing competitions for food supply
- these changes have been linked to global warming
What does a study of bird nesting in mid-1990s show?
a study of bird nesting in the mid-1990s discovered that 65 species nested an average of 9 days earlier than the 1970s
How are Antarctica ice cores used to act as evidence for climate change?
- They are known as proxy data, data from before official records were kept
- The layers of Antarctic Snow remain untouched by humans and as they build up they present a picture of the climate of the times
- They use oxygen isotopes within the ice to work out what the temperature would have been like
- Additionally, when the ice melts methane and CO2 are released which can be compared to present levels to see the differences between climate then and now
- More accurate than ocean sediment
When did reliable weather records begin?
1910
How far back can ice cores be used to see the atmosphere?
800,000 years
How can ocean sediment act as evidence for climate change?
can use fossil evidence that is collected within the sediments to determine what the climate and conditions would have been like previously such as past surface water temperatures, levels of oxygen and nutrients
Eccentricity:
describes the path of the Earth as it orbits the Sun
How may eccentricity be a cause of climate change?
- Earth’s orbit not fixed - it changes from being almost circular to being mildly elliptical
- a complete cycle from circular to elliptical and back to circular again occurs about every 100,000 years
What does the Earth spin on and what does this cause?
the Earth spins on its axis, causing night and day
How might axial tilt be a cause of climate change?
- the Earth’s axis is currently tilted at an angle of 23.5 degrees
- however, over period of approx. 410,000 years the tilt of the Earth’s axis moves back and forth between 2 extremes - 21.5 degrees and 24.5 degrees
What is precession?
precession describes a natural “wobble” rather like a spinning top
How may precession be a cause of climate change?
- a complete wobble cycle takes about 26,000 years
- Earth’s wobble accounts for certain regions of the world e.g. northern Norway experiencing very long days and very long nights at certain times of the year
How may solar output be a cause of climate change?
scientists identified cyclical changes in solar energy output linked to the presence of sunspots
What is a sunspot and how doe the number of sunspots change?
- sunspot is a dark patch on surface of Sun that appears from time to time
- number of sunspots increases from a minimum to a maximum and then back to a minimum over a period of about 11 years
- 11 year period is called the sunspot cycle
How may maximum sunspot output affect the climate?
- when sunspot output is at a maximum the Sun gives off more heat
- large explosions occur on the surface of the Sun resulting in solar flares
How may minimum sunspot output affect the climate?
- when sunspot output is at a minimum the solar output is reduced
- can lead to lower temps on Earth
When has low sunspot output affected the climate on earth?
- very few sunspots observed between years of 1645 and 1815
- coincided with coldest period during so-called ‘Little Ice Age’ when Europe experienced a much colder climate with severe winters
What do violent volcanic eruptions do?
violent volcanic eruptions blast huge quantities of ash, gases (such as carbon dioxide) and liquids into the atmosphere
How may volcanic activity be a cause of climate change?
- fine particles of ash can block out the Sun, leading to a short-term reduction in surface temperatures called a ‘volcanic winter’
- in the cold lower atmosphere, sulphur dioxide is converted to sulphuric acid by the Sun’s rays reacting with water vapour
- these fine aerosols act like tiny mirrors reflecting radiation from Sun
- can lead to longer term cooling lasting up to 3 yrs