The Icy Epoch Section 3.2

The Great Melt! The great melt – Following the Pleistocene Ice Age, a great period of warming and melting occurred. – This opened up most of North America for inhabitation by people The oldest archeological evidence of humans living in North America is from 16,000 years ago

Are we still in an Ice Age? – If you are using the correct definition, yes we are still in an ice age! Ice age – defined as a period when ice sheets cover parts of the northern and southern hemisphere. Glaciations are periods when continental ice sheets cover large regions of north America and northern Europe. People commonly refer to this as an ice age.

Changing Life Forms 0 We have plenty of evidence that the plants and animals we find on our planet today were not the same as those found a million years ago 0 Evidence comes from: 0 The fossil record 0 A record of changing atmospheric, water and climate conditions 0 The continual discovery of new species 0 The ongoing evolution of life forms (more about this in the bio unit!)

Changing Climates A variety of evidence exists to demonstrate that the climate of the Earth has varied throughout its history This change continues today, and is often referred to as global warming – Some of the evidence we use depends upon humans, so only describes the last few thousand years – Some of the evidence allows us to look back at the Earth’s conditions prior to humans arriving

Types of Evidence Two general categories of evidence exist: – Anecdotal evidence Evidence based on stories people tell, From the word “anecdote”, meaning a short, personal story of an individual’s experiences Is most often qualitative in nature – Instrumental evidence Includes any evidence that comes as a result of measurement May require special equipment, Is most often quantitative in nature

Taking Evidence When trying to measure something, there are two approaches – Measure the factor directly (e.g. if you want to find out how far it is to Calgary, measure the distance) – Measure some other factor, and use it to make conclusions (e.g. calculate the distance based on your speed of travel and the time it takes)

Tracking Climate Direct evidence – Explicitly indicates global warming is occurring, based on an actual change in global temperatures. Indirect evidence – Evidence that seems to support the idea of climate change but does not involve a direct measurement of temperature.

Direct Evidence Uses historical data – From scientists to farmers, people have been recording weather and temperature information for hundreds of years – Patterns emerge and are often used to predict future weather, such as in the Farmers’ Almanac Limited in how far back a written record goes; restricted only to the last few hundred years

Indirect Evidence Different types of evidence exist that support the idea of climate change, though are not direct measurement of temperature These include: – Tree ring analysis – Ice core sampling – Fossil record of insects – Pollen sampling from the bottom of lakes

Tree ring analysis 0 Tree rings reflect the changing seasons of cold and drought, warmth and precipitation during the life of a tree 0 By examining wood from trees of different ages and from different time periods, a continuous record of climate changes can be established that goes back a few thousand years. 0 The tree's age can be figured out by counting the pairs of light and dark rings. It's easier to see the dark rings so they are usually the ones used for counting.

Tree Ring Analysis To help figure out what climate the tree grew in and what the environment was like, the scientist looks at each ring: – Thickness: How wide a ring is can tell you if the environment was good or bad for the tree to grow in In years when the amount of rain and temperature were good a tree's rings are wider. In bad years a tree's rings are thinner. – Shape: » If rings start to become thinner on one side than the other it probably means the tree is leaning over to one side. » High winds or a big storm can cause a tree to lean. – Strange marks or scars, » Can be left by insects or disease. » A forest fire can leave burnt marks.

– Scientists use a computer to measure the width of rings up to 0.01 mm and to find other things they can't see by just looking at the tree.

Ice Core Sampling By obtaining a sample of a column of ice 10,000 feet down in our ice sheets, we are looking at ice made over 700,000 years ago – By analyzing the tiny bubbles of air trapped in this ice, scientists can collect information about The quality of the air at that time, – CO 2 levels – Approximate air temperature.

Fossil Records and Pollen Samples 0 By examining fossil records or pollen samples from the past, we can determine what plants and insects existed at that point in Earth’s history 0 Since we know that plants and animals are adapted to particular climates (temperature, humidity, amount of sunlight), we can make conclusions about the conditions in the area in which they were found 0 Fossil records & the Burgess Shale 0 In Alberta, we are lucky to have a very detailed fossil record for one particular period of time known as the Cambrian Era 0 the Cambrian era was a period of great and rapid change in the diversity of life found on Earth 0 the Burgess Shale is found on the side of Mount Wapta in the Rocky Mountains, and is known worldwide for its well- preserved fossils

Fluctuation Temperature – The current period of global warming is only one example of climate change in Earth’s long history – We don’t know for sure what causes the change in climate, but we do have some theories Continental movement Global conveyer Wobbly Earth Solar fluctuations

Continental Movement – Plate tectonics are random, and North America and the other continents have been in many positions of over time – But evidence has shown that glaciation occurs only when large land masses (continents or large countries like Greenland) are near the poles – As a continental ice sheet begins to form, the snow and ice reflect the sun’s rays back into space, and the entire planet - not just the frozen areas - experiences a global cooling period

Global Conveyor 0 Remember from Science 10, water has a high specific heat capacity. That means: 0 Coastal areas like Vancouver have a more temperate climate than in Edmonton, where climate fluctuates 0 The huge volume of ocean water is capable of transferring a tremendous amount of heat 0 Remember convection currents from the rock cycle? 0 The oceans have giant convection currents that transport heat in a similar way 0 The global conveyor is the system of these ocean currents that circulate warm water away from the tropics and cool water away from the poles

Global Conveyor con’t 0 This explains why many European cities are warmer than Canadian cities at the same latitude (distance from the equator) 0 Antarctica has it’s own ocean current that recirculates the cold water around the entire continent 0 This explains why Antarctica is the coldest place on the planet 0 If the glaciers in Antarctica melt, there would be a significant rise in the water level of the oceans, and many parts of the world would experience major flooding

Practice Problem Fully explain how an increase in CO 2 emissions could cause the ocean conveyor to weaken or reverse.

Wobbly Earth – While we often illustrate the rotation of the Earth looking like this: – Actually, it’s more like this:

Wobbly Earth Its orbit actually varies in three ways: – The shape of the orbit – The tilt of the axis of rotation – The wobble of the axis of rotation This means that every once in awhile, the three factors combine to make a part of the Earth at maximum possible distance away from the Sun – These points in Earth’s orbit coincide with the timing of the Pleistocene Glaciations

Solar Fluctuation – While our Sun doesn’t show any sign of giving up shining anytime soon, it doesn’t always shine with the same intensity The variations in energy output are small, only 0.1% to 0.2% However, there does seem to be a correlation between a low frequency of sunspots (indicating additional solar energy being released) during particularly cold periods of human history, such as the Medieval Ice Age in Europe from

So really, what’s the big deal? So then what’s the big deal about global warming – If the Earth has experienced global warming and cooling periods throughout its history, why the concern with global warming now? Isn’t it just a natural part of our planet? – There are two reasons for concerns about this global warming period: The degree of change (How much it’s changing) The rapidity of change (How fast it’s changing)

Homework Pg #1-9 Pg #1-4