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Causes and Consequences of Climate Change (minds-on)
Climate change and the construction of homes and buildings
The significance of climate change
Measuring past climates
Climate change - examining the evidence
Some people argue that climate change is part of a natural cycle that humans have little to do with
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Sources of long-term climate change data
Earth has been through 5 major ice ages in the past 2.4 billion years
If current climate and atmospheric conditions were to be found to exist in the past (before humans started to burn fossil fuels) then humans would not have been responsible for climate change
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Causes and Consequences of Climate Change(action)
Exploring elements of past climates
Tree rings
Sea-floor sediments
Ice cores
Other courses of long-term climate data
Soil layers
Can be examined for changes in pollen abundance which indicates changes in vegetation (relates to climate)
Corals
Fossils
Lake sediments
Growth rings in fish bones
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Causes of climate change
Natural causes of climate change
Changes in Earth’s orbit
Eccentricity - the shape of Earth’s orbit changes slightly over a period of about 100,000 years
Tilt - the tilt of the Earth’s axis varies a few degrees over a period of 41,000 years
Precession - Earth’s axis rotation wobbles a bit over a period of 23,000 years
Movement of the continents
The long-term cause of climate change is continental drift or plate tectonics
Section of the Earth’s crust are called plate which moves up a few centimetres a year
Over million years these few centimetres can make a huge difference
The changes of the continents and their position affect wind patterns, ocean currents, and the amount of solar radiation reflected back into space
Changes in solar radiation levels
Some scientists think that sunspots can be a short-term cause of climate change
Sunspots are regions on the sun’s surface (have slightly lower temperatures)
The number of sunspots can change over 11 year-cycle
The amount of energy given off by the sun increases very slightly when the number of sunspots increases
If the sun emits more energy during one of these increases it could affect the climate
The sunspot cycle is unlikely to cause changes of major climate change
Volcanoes
Can be a short-term cause of climate change
Large eruptions release huge amounts of gases and volcanic ash into the atmosphere
Sometimes enough to create thick clouds that block incoming solar radiation
This cools the planet for a few years
Some volcanic activity in the past may have caused large amounts of carbon dioxide into the atmosphere
Leading to the greenhouse effect and warmer global temperatures
Collision with asteroids and comets
Depending on the size of the object it could devastate continents
Could lead to global cooling lasting for centuries
The extinction of dinosaurs was likely caused by climate change brought on by a large asteroid hitting Earth
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Anthropogenic Causes (human causes)
Adding of greenhouse gases
Like burning fossil fuels (especially CO2)
It started about 250 years ago
The atmospheric concentration of CO2 has increased 31% since 1750 (when it was 280ppm)
Continues to increase 1.5ppm or 0.4% per year
About 80% of anthropogenic emissions of CO2 during the past 20 year has been due to the burning of fossil fuels and cement production (rest is deforestation)
Methane (CH4) and nitrous oxide (N2O) have increased since 1750
Removing vegetation
Deforestation
During the last 50 years, forests all over the world have been clear-cut at an incredible rate
It is very true in tropical regions
Deforestation contributes to climate change in 2 main ways
Wood is often being burned or decomposed releasing large amounts of CO2 into the atmosphere
The cleared land is usually not reforested, so there is no vegetation to take and store the CO2 for long periods of time
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Is climate change happening now?
Scientists are tackling this question by examining 3 main types of evidence
Global temperatures
Individual temperatures are taken every day around the world at several different stations
Scientific analyze temperatures changes in order to discern trends
One method is temperature anomalies - is a temperature value obtained by comparing the measured temperature to some average temperature
Ice
The most noticeable effects are the melting of ice
Scientists have found that the amount of ice at the poles, in Greenland and in glaciers around the world is decreasing rapidly
Sea-level rise
2 reasons they can rise
Thermal expansion - water expands as it warms up, as the ocean heats up their volume expands
Ice melts on land - if it melts on land it will flow into the ocean
Scientists estimate that if all the land ice in the polar regions were to melt, sea levels would go up 25 meters
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Investigating Earth’s Future Climate
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Earth’s Future Climate
Predicting our future climate
Modelling Climate Change
Positive Feedback Loops
The effect of process amplifies that process
Ex.
The albedo produced by snow and ice, the snow on the ground in the Arctic produces an overall cooling effect because it reflects sunlight back into space
However if the global temperature increases then it cause the Arctic snow to melt and the albedo effect decreases
The exposed ground is darker than the snow so it absorbs more heat from the sun causing more melting
Climate models can be very sensitive to small changes in conditions
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What makes a good climate model
Multiple Effects
Trees are carbon sinks because they remove carbon dioxide from the atmosphere
If trees are cut down more carbon dioxide will be left in the atmosphere gaining the global temperature
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Breaking Down the Information and Misinformation
Why the Controversy?
Reliable Sources and Information
Are Scientists Undecided
Steps Towards a Solution: Global Action
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