It is a unicellular organism. Yeast are a polyphyletic group of species within the kingdom fungi. They are predominantly unicellular.
Climate variations are averaged by using weather conditions from past years. Climate variability varies by seasons, because some seasons get colder than others, and there could be more precipitation in the atmosphere, which would then make it easier to calculate future rainfall, making people aware of storms that are coming ahead of time and allowing them to prepare for it (making storm water drains, etc.).
