Week Two of past Climate Change: Challenges and Solutions focused on past climate change. Part One, from an ancient perspective (4.5 billions through to hundreds of millions of years), including the idea of snowball earth, with Part Two exploring more recent past climate change, over the last two million years (quaternary period). Evidence is presented to illustrate what we know about climate changes during these periods.
Pt1 The climate has been regulating itself for the past 4.5 billion years, during that time two complex puzzles occured and the feedback loops that explain them need attention.
Puzzle One is around 3.8 billion years ago, when the engine of Earth climate, the Sun was 25-30% less bright than it is now. Earth should have been 20° colder than it is now, but it wasn’t,….due to thick blanket of CO2, where did this blanket go? Feedback loop of chemical weathering. Weak mix of CO2 in rainwater (carbonic acid) dissolves silicate rock, washes into oceans, creatures make shells, die and turn into deposits of carbonate rocks. This climate system includes interaction between ATMOSPHERE-HYDROSPHERE-BIOSPHERE-LITHOSPHERE
Puzzle Two took place 2.2 billion and 700 million years ago…Earth had two very cold periods and the theory of Snowball Earth is explored. Ice albedo reflects radiation, if cooling is sufficient ice increases, absorption of sunlight is reduced, increased albedo…positive feedback loop. If ice reaches 30° latitude a tipping point is reached and ice can cover all of earth’s surface…. This diagram explains Snowball Earth feedback mechanisms. Volcanic activity and the resulting CO2 would at some point reverse the process and the earth would heat up again. Part one finished by considering how Earth, unlike Venus and Mars, currently occupies a habitable zone in space.