Earth’s Climate: Out of Balance

9.1 – Evidence of a Changing Climate

Scientists have evidence that our Earth’s climate is changing again

The difference this time is that the change is a direct result of human activities

There are many factors that are studied, including:◦ Temperature◦ Glaciers, ice sheets, and sea ice◦ Sea level◦ Weather, precipitation patterns and seasons

Evidence of Climate Change

Studying past temperature records helps scientists to predict what kind of temperature trends are normal

Rising Temperature

In Canada, average national temperatures have increased by 1°C in the last 55 years

Over the western and northern parts of the country, average temperatures have risen even more (up to 2.5°C in the Yukon!)

Effect on Canada

The average size of glaciers around the world has decreased as the global temperature has risen

Nearly half the world’s population is dependent on glacier melt waters as their main water source; this could lead to water shortages!!

Ice sheets over Greenland and Antarctica are also disappearing at a rapid rate

Melting Glaciers, Ice Sheets,and Sea Ice

Even sea ice is affected – an area of sea ice equivalent to Ontario and Quebec disappeared from the Arctic Ocean in September 2007

It is estimated that the Arctic could be ice free during the summer time in only a few years!

Rising Sea Level

When glaciers and ice sheets on land melt, water runs into the ocean, causing the sea level to rise

If the Greenland ice sheet was to melt completely, this would cause the global sea level to rise by about 7 m!

But, are there other factors other than temperature that are causing sea levels to rise?

Water expands when it warms up – this is known as THERMAL EXPANSION

It is believed that this is the cause for much of the sea level rise in the past 120 years

Thermal Expansion and Sea Level Rise

Changes in Severe Weather◦ Heat waves have become more common◦ Hurricanes have intensified due to the warmer

ocean temperatures

Changes in Precipitation Patterns◦ In the northern hemisphere, we are getting

more of our precipitation as rain instead of snow

◦ Total precipitation is increasing in northern Canada but decreasing in southern Africa and Asia, as well as the Mediterranean

Changing Seasons◦ Amount of snow on the ground is decreasing◦ Very cold days and frosty nights are coming later in

the year and ending earlier in the spring, leading to longer growing seasons

Changing Ecosystems◦ Trees, shrubs are flowering earlier◦ Animals are breeding earlier◦ Animal and plant communities are migrating towards

the poles and higher altitudes as the regions around them warm up

◦ This leads to undesirable insects and plants in these new regions

◦ E.g. Mountain pine beetle in B.C., where in the past it was too cold for the beetle to survive

9.4 – Greenhouse Gases: Changing the Climate

Greenhouse gases have always been a part of our atmosphere, but over the past 200 years the levels of these gases has dramatically increased

Production of additional greenhouse gases is a result of the combustion of fossil fuels in energy production, transportation, and industry

Scientists have studied the intake and output of greenhouse gases and have concluded that the increase is likely due to human activities

Greenhouse Gases

“Anthropogenic” means human-produced The main anthropogenic GHG’s are:

◦ Carbon dioxide◦ Methane◦ Nitrous oxide◦ Chlorofluorocarbons (CFC’s)

Anthropogenic Sources of GHG

CO2 is the most significant GHG

Burning fossil fuels (coal, gasoline, natural gas) produces CO2

Forests are important in the elimination of CO2 from the atmosphere

Trees take in CO2 from the air to use in photosynthesis

Carbon Dioxide (CO2)

Trees take in carbon from the atmosphere and store it in a new form (glucose)

This is why trees are referred to as “carbon sinks”

Emissions of CO2 are a result of many things, but 10% is directly related to deforestation

This prevents forests from absorbing more carbon and releases some of the stored carbon back into the atmosphere as CO2

Carbon Dioxide (CO2) Con’t

Agricultural activities such as rice farming and cattle ranching produce methane

It is also produced from the decay of organic materials in landfills and sewage treatment plants

Coal mining and natural gas extraction also releases methane gas that was trapped underground in fossil fuel deposits

Methane (CH4)

About 2/3 of nitrous oxide emissions comes from the management of livestock feed and waste

The rest comes from nitrogen fertilizers, industrial processes, and fossil fuel use

CFC’s are commonly used as refrigeration agents

They leak out of refrigerators and air conditioners or are released by industrial processes

Nitrous Oxide (N2O) and CFC’s

Scientists compared past climate data with current data to see how much of an effect anthropogenic GHG’s were having on global temperatures

Scientists studied ice cores to collect data up to 800 000 years old!

To this date, scientists are not able to prove that increases in CO2 concentrations cause global temperatures to rise or vice versa

There is, however, a correlation between the two!

GHG’s and Global Temperature

We studied earlier how the Earth absorbs radiation from the sun (converts it to thermal energy) and radiates low energy infrared radiation back into space

This IR radiation is being absorbed by the atmosphere instead due to the high concentrations of GHG’s in the atmosphere

30% of the GH effect is caused by [CO2] 20% and 10% of the GH effect is caused by [CH4] and

[N2O] respectively

The main problem here is that humans are ENHANCING the natural greenhouse effect!!

The Anthropogenic GH Effect

Global Temperatures and CO2

•CO2 levels cause an increase in global temperatures•However, increases in temperature also cause increases in CO2 levels

•Rising temperatures over the past 400 000 years increased the release of CO2 stored in plants and oceans (carbon sinks)

•Since CO2 is a GHG that traps thermal energy inside the atmosphere, the rising temperatures cause the CO2 levels to increase, therefore causing the temperature to increase even further!

9.5 – Canadian Emissions of Greenhouse Gases

What is our Contribution? On average, individual Canadians emit more

GHG’s than most people in the world (we rank in the top 10!)

Alberta is the province that produces the most GHG’s, followed by Ontario

These GHG’s are mainly caused by:◦ Gasoline burning in car/truck engines◦ Coal-based power plants◦ Manufacturing and other industrial processes◦ Natural gas heating systems in homes (Methane

is the main component of natural gas)

Canadian Sources of GHG’s

Canadian Forests: Source or Sink?•Canada has about 400 million hectares of forest, which is one of our most valuable resources

•Forests can sometimes be a source of carbon due to things like:

•Insect damage – kills trees, speeding up decomposition and increasing CO2 emissions

•Wildfires – release CO2 gas

•Deforestation – GHG’s like CO2 and CH4 are released when trees are cut down

9.6 – Computer Modelling: Evidence that Human Activity is Causing Change

For scientists to accurately study the effect of GHG’s on the Earth’s climate, they need to conduct a controlled experiment with a second “Earth” that has no people

This would allow them to compare the research for our current climate models with data that would mimic climate conditions without the presence of human activity

Scientists have developed detailed computer models that represent important components of the climate system

These models are used to create simulations of Earth’s climate under different conditions

Modelling our Climate System

Computer Modelling

Scenario #1: Natural Changes ONLY Scenario #2: Natural and Anthropogenic Changes

This shows what Earth would be like with no human activity

It considers the following factors:◦ Changes in energy from

the sun◦ Volcanic eruptions◦ Natural processes that are

part of the Earth’s climate system (e.g. Natural emissions of GHG’s)

This scenario models an Earth that includes natural changes and changes influenced by human activity

•In scenario #1, Earth’s average temperature stays relatively the same

•In scenario #2, Earth’s average temperature increases, particularly over the last 50 years

First, even a temperature change of 1°C or 2°C warmer will have dramatic effects on ecosystems worldwide. The main concern is the speed at which these changes are taking place.

This temperature change is problematic because it will be higher than any increases seen in the last 800 000 years!

Lastly, while human civilization has been able to adapt to recent climate conditions, it is unknown as to how much adaptation would be required for life to continue as we know it

So, Why Are We Worried??