The atmosphere is like a blanket that is wrapped around the Earth.  It protects the planet and normally keeps us at a comfortable average temperature of 14°C.

Human activities, like burning coal and gas, add greenhouse gases like carbon dioxide to the atmosphere. The more these gases build up in the atmosphere the more heat is trapped, the same way more heat is trapped under a thicker blanket. 

This heats up the atmosphere and raises Earth’s temperature – what is called global warming.

This human-caused global warming is happening 30 times faster than natural periods of warming that happened in the past.

Climate change describes all the changes that are happening because humans are warming the planet.

As the Earth gets warmer, the air patterns and ocean currents that drive climate can change. This affects things like how hot or cold places are, how much rain or snow falls, how severe storms are, or how often and where storms happen.

GLOBAL WARMING

CLIMATE CHANGE

Every year, Hudson Bay shifts between being dominated by ice to being dominated by open water.

• In November, the Bay is still open having absorbed the Sun’s warmth all summer. The water is radiating heat into the cold air.

• As temperatures drop, thick sea ice forms and covers the Bay during winter. The Bay is still ice covered at the end of April.

• The ice breaks up in May and June, and by August the Bay is typically ice-free open water.

But warmer temperatures from climate change are leading to less sea ice and causing the ice cover season on Hudson Bay to shorten by 20 days since the 1980s and 90s.

Why does ice cover matter?

Hudson Bay affects temperatures as far as 500 km inland. Cooling in spring and summer comes from cold sea breezes blowing in from the ice on the Bay.

When the ice cover season is cut short, there is less cold wind blowing south. This leads to warmer temperatures in areas like northern Ontario, affecting the plants and animals that live there.

A longer open water season also makes the Bay continue to warm. In the past, water temperature would reach about 9°C in late summer, but has recently reached as high as 12°C. This is because the dark colour of the water is better at absorbing the Sun’s energy, while white sea ice better reflects that heat.

Cold air sits over the north end of the Earth while warmer air sits over the Equator. Where the cold Arctic air meets the warmer air to the south is called the polar front, and is accompanied by the polar jet stream, high speed, high altitude winds that circle the northern half of the planet.

The polar front and the jet stream play an important part in the weather patterns of the northern hemisphere. But research suggests that warming in the Arctic can alter the polar jet stream, changing its shape to become more wavy or slowing it down to a near stop. Like a loose bike chain, the jet stream becomes more wobbly, causing cold polar air to move further south in some areas and warm southern air to move further north in others.