1. Evidence of a Changing Climate

2. Climate Change
Although Earth’s climate has changed in the past, today scientists who study climate believe that changes are because of human activities. Evidence of these changes are closely being monitored

3. Rising Temperatures
Scientists use data from weather stations to calculate the average temperature each year going back more than 100 years
Average temperature goes up and down each year
Long-term Trend shows a rise in temperature from the early-1900s to the mid-1900s, followed by a plateau (relatively even), and another continued rise in the 1970s

7. Increasing Temperature
Six of the last seven years are in the top ten hottest years ever recorded
In northern parts of the world, including the western and northern parts of Canada, the average temperature is increasing even faster than the rest of the world

8. Increasing Temperature

9. Melting Glaciers, Ice Sheets, and Sea Ice
Average glacier size has decreased over the last few decades
Almost half the people in the world depend on glaciers for their water  leading to water shortage in some regions
The ice sheets of Greenland and Antarctica, as well as Arctic sea ice are also disappearing at a faster rate
Ice sheet – A glacier that is more than km wide, covering the land it is on.

10. Melting Glaciers, Ice Sheets, and Sea Ice
Arctic sea ice melts in the summer and refreezes in the winter.
The ice that disappears in the summer has been increasing over time

11. Rising Sea Levels Global sea level has risen over the past 120 years
Risen twice as fast since compared to the previous 30 years
Small increases can result in floods in low-lying countries
When glaciers and ice sheets melt, water enters the oceans, increasing the sea level

12. Rising Sea Levels
Glaciers an ice sheets are not melting fast enough to account for all the changes in sea level
Thermal Expansion and Sea Level Rise
Water expands slightly when it warms up  Thermal expansion
As temperature increases, the volume of water increases
Another reason?
Additional water may be coming from the North American groundwater supplies (which have decreased)

13. Changes in Severe Weather
Heat waves are becoming more intense
Hurricanes have become stronger over the last 50 years, fuelled by warmer oceans

14. Changes in Precipitation Patterns
In the northern hemisphere, more precipitation is falling as rain and less as snow
Other regions in the world are becoming drier

15. Changing Seasons
Decrease in snowy days throughout the northern hemisphere
Decrease in very cold days globally  these days are coming later in the year and ending earlier in the spring
Because cold weather is beginning later in the year and ending earlier, many regions are experiencing longer growing seasons.

16. Changes in Ecosystems
Growth patterns are changing  plants are flowering earlier
Some animals begin their mating/breeding period earlier
Migration of plants and animals towards polar regions and higher altitudes because it warming up
Undesirable insects and plants are also moving into these areas