A 2-degree Centigrade change in temperature has already happened in some places.
Two degrees centigrade is supposed to be the point of no return for major climate impacts to all forms of plants, animals and humans inhabiting this place we call Earth. In this Washington Post article, Dangerous new hot zones are spreading around the world, they call out the fact that the 2 degree Rubicon has been passed in some parts of the world already.
Based on my previous reading, having the frozen tundra warm is a worst-case situation since there is an abundance of carbon trapped in the frozen ground. When it thaws, there will be a massive release of carbon that can hyper-feed the rate of climate change throughout the world. I guess there will be those who point to that event as being naturally occurring and not connected to humans.
But then there is this article on how attitudes toward the cause of climate change may be finally changing here in the United States, see Americans increasingly see climate change as a crisis, poll shows.