02082011

What is weather and climate?

What's the difference between weather and climate?

First off, we need to establish that both terms, namely weather and climate, both refer to an atmospheric system; i.e. usually the Earth's atmosphere.

The difference between weather and climate is as follows. Weather is atmospheric effects that can experienced over a period of minutes to days. Where as climate is usually the 'configuration' the whole atmospheric system experienced over a period of months to years. So basically weather is something you can directly experience where as climate is trends that occur over a much longer time frame.

The other difference is that weather is something that can be forecast a few days in advance with rapidly decreasing accuracy the further into the future you go.

Now predicting climatic events in the far future, i.e. tens to hundreds of years, is a completely different proposition to forecasting the weather. The trouble is that the climate over the longer term is not a 'stable' system, both in terms of how the systems acts but in what forms the parts of the system. Its bit like predicting the time on a clock when the rate of the clock running changes along with the precise configuration of all the gears over time; very quickly you get into a situation where there is so much unpredictable change that the confidence in those predictions is nearly zero...



And this is the real problem that climatic modeling faces, the future is unknown and very ill defined; the only real consistent guide to baseline behavior is what has happened in the past. We know certain things, like the Sun and our orbit have a dramatic effect on the climate we experience. We also know planetary events, like volcano eruptions can 'perturb' the climate over a few to many years.