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.
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Presentation on theme: "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."— Presentation transcript:
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
Studying past temperature records helps scientists to predict what kind of temperature trends are normal
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!)
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
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!
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
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
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
“Anthropogenic” means human-produced The main anthropogenic GHG’s are: ◦ Carbon dioxide ◦ Methane ◦ Nitrous oxide ◦ Chlorofluorocarbons (CFC’s)
CO 2 is the most significant GHG Burning fossil fuels (coal, gasoline, natural gas) produces CO 2 Forests are important in the elimination of CO 2 from the atmosphere Trees take in CO 2 from the air to use in photosynthesis
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 CO 2 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 CO 2
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
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
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 CO 2 concentrations cause global temperatures to rise or vice versa There is, however, a correlation between the two!
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 [CO 2 ] 20% and 10% of the GH effect is caused by [CH 4 ] and [N 2 O] respectively The main problem here is that humans are ENHANCING the natural greenhouse effect!!
CO 2 levels cause an increase in global temperatures However, increases in temperature also cause increases in CO 2 levels Rising temperatures over the past 400 000 years increased the release of CO 2 stored in plants and oceans (carbon sinks) Since CO 2 is a GHG that traps thermal energy inside the atmosphere, the rising temperatures cause the CO 2 levels to increase, therefore causing the temperature to increase even further!
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)
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 CO 2 emissions Wildfires – release CO 2 gas Deforestation – GHG’s like CO 2 and CH 4 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
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