Dr. Mathews: One of the reasons things are so uncertain comes because of feedback loops. Imagine this scenario, it warms up, snow melts. Because the snow melts it reveals more land. Well the land will warm up more because it is receiving more energy. When there is snow or ice on the ground, when there is sun light, much of it gets reflected back up into space. When you go skiing, one of the key items of your equipment is goggles. Snow blindness is a very real threat because so much more light gets bounced from the surface into your eyes that in fact you can actually go blind. It is a very similar things with clouds. World War 2 pilots would wear sun glasses and if they are fighting in Europe it is not because of the English weather. When you are flying above clouds, again a lot of that light gets reflected back off the surface of the clouds because of the whiteness and it impacts how much energy reaches the surface of the planet. So back to the snow, snow melts, revealing more land the land warms up, the climate warms up, more snow melts. More snow melts, revealing more planet, more warmth from earth's land. This is a cycle. And it can happen the other way. We think ice ages, what happens is it snows, more energy is reflected. Then it gets warmer. Then it snows some more, more energy is reflected, the planet gets colder. It snows some more. A lot of these feedback loops will be happening and they can have a very drastic on how one assigns climate change models.