Evidence of a Changing Climate

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

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

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

Increasing Temperature

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 50 000km wide, covering the land it is on.

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

Rising Sea Levels Global sea level has risen over the past 120 years Risen twice as fast since 1993 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

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)

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

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

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.

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