Why Did The Vikings Leave Greenland?

Here is my explanation as to why I think they abandoned their settlements and went back to Europe!

Tipping Points

The tipping points that I found in Emanuel (2007), UC Berkeley News Center, and Scientific American:

• Periodic oscillations of the Earth's orbit that primary effects the Earth's orientation
• Water vapor accumulates in the atmosphere, causing the atmosphere to warm, allowing more water vapor to accumulate
• Ice and snow can accumulate, making it's way toward the equator. The ice and snow would reflect sunlight back into the atmosphere causing the planet to continue cooling
• Arctic Sea ice has essentially diminished past a certain threshold, claiming that it will be a relatively rapid increase to losing all of the ice
• Major changes in the ocean currents or air circulation 
• Ocean temperatures or acidity

Quaternary Period

Here is my description of the Quaternary Period along with a figure, enjoy!

What Caused the Ice Ages?

In order for the Ice Ages to occur, it was not just a simple cause and effect. There are four things that have to occur before an Ice Age begins. The first thing that needs to be set up would be the boundary conditions. This means that the position of the continents would have to be further north, to allow an ice sheet to be formed. Also having tectonic plates collide, creating mountains, would emit less CO2 in the air. The second thing needed is the trigger, which has to do with the Earth's rotation around the Sun. With the boundary conditions pushing the Earth towards a tipping point, a small trigger like the Earth being just a little bit farther from the Sun can trigger dramatic changes. Feedbacks occur when the ice and snow cause the Earth's albedo to reflect more of the energy and absorb less. This causes the planet to get colder, pushing it to create more snow and continue the effect. The tipping point then occurs as the snow and ice begin to build up, the globe gets colder and glaciers begin to form. This is how the Ice Ages began.

The Figure above shows the variation that the Earth can have when orbiting the Sun. When Earth becomes too far away, it creates a great environment to host an Ice Age.

Source: here