Climate Change - Exploring Elements of Past Climates, Predicting our Future Climate

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Causes and Consequences of Climate Change (minds-on)

Climate change and the construction of homes and buildings 

• The construction of homes and buildings have also been impacted by climate change 
• Along with forests, oceans, and farmland

The significance of climate change

• Climate change can lead to the extinction of animals, monstrous hurricanes, and spread to certain diseases 

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 

• Examining trees that are hundreds or even thousands of years old is a way to better understand recent climates 
• Every year a tree grows a new layer of wood under its bark which is called the tree ring
• The thickness of the ring depends on the temperature and precipitation during the year that it was formed 
• So each growth ring preserves a record of the climate for that year

Sea-floor sediments 

• Using materials for the seafloor can be used to reconstruct past climates 
• The sediments include shells of tiny organisms that once lived at the surface of the oceans 
• When they die off their shells sink to the ocean floor and settle into the mud 
• The type and number of these organisms alive at the surface depending on the water temp.
• By studying these scientists get an idea of the changes in ocean temp. overtime

Ice cores 

• Past climate can be predicted by studying the air bubbles trapped in samples of very old ice
• Taking ice core examples like the glaciers of Greenland and Antarctica
• The air bubble inside the ice contains tiny samples of atmosphere when the bubble was formed 
• Using the ice cores we can measure the temperature (from isotope ratios) and the amount of CO2 and other greenhouse gases present in the atmosphere

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

• Predicting our future is a process that is called the scientific method and it involves;
• Analyzing data 
• Determining relationships 
• Making predictions 
• This process is not controversial as it emphasizes an important aspect of science (and its dynamic)

Modelling Climate Change 

• Climatologists use sophisticated computer programs to model Earth’s climate
• The computer programs use quantitive methods to simulate the interactions of the atmosphere like oceans, land surface, clouds, and ice
• The computer models use equations to connect parts of the system 

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 

• If the model can closely replicate what we know already happened then we can predict the future better
• Clouds are an example of how multiple combined effects plus feedback loops can create complicated situations
• The amount of cloud cover depends on the following 
• Evaporation
• Sunlight
• Ecozone features
• Temperature
• Precipitation
• But they can also be involved in feedback loops with each factor 
• This intertwined series of interactions make it hard to clear cause and effect relationships
• The best climate models are able to predict that global temperature will increase 3 degrees C within the next 50 years 
• The heat won’t spread evenly, tropical regions will receive less while polar regions will experience 4-5 degrees C

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?

• Switching to alternative energy sources causes money in the short term but in the long run, it will save us money
• Some people think that climate change is natural and it varies 

Reliable Sources and Information

• Most of the scientific work that is done on climate change is published in technical journals (most people don’t read)
• In 1988 the United Nations set yo the IPCC (Intergovernmental Panel on Climate Change)
• This is run by WMO (World Meteorological Organization) under UNEP (United Nations Environment Programme)
• IPCC published several small reports and updates on the developments of climate change 

Are Scientists Undecided 

• Scientific organizations like the Canadian Meteorological and Oceanographic Society and the Canadian Foundation for Climate and Atmospheric Sciences agree with IPCC’s conclusion 

Steps Towards a Solution: Global Action 

• Since the 1980s the UN has sponsored international meets to examine the problem and proposing solutions
• One of the most famous proposals was presented in 1997 in Kyoto, Japan
• The Kyoto Protocol called for every industrialized nation to reduce its output of greenhouse gases emissions by 6% below their 1990 levels by 2012
• Canada signed this agreement but later withdrew in December of 2011
• In the Paris Agreement formed in December of 2015 195 countries signed the first-ever legally binding global climate deal