Weather versus Climate

Weather versus Climate

The key difference between weather and climate is really a matter of time scale.

  • Weather is what we experience over the course of hours, days, and weeks.
  • Climate is the average of weather over years, decades, and longer.

Or, as the old adage goes: climate is what you expect, weather is what you get.

Forecast models are used to predict specific weather events. To do that, they start with the initial conditions and simulate how those conditions will evolve with time. Getting the initial conditions right turns out to be very important in forecasting weather events. The goal of those who develop and use these weather forecast models is to predict weather with enough accuracy to help those who may be affected by it.

On the other hand, climate models are used to generate the statistics (such as the mean and variability) of weather phenomena, not predict the time and place at which the phenomena will occur. So, while climate models simulate weather phenomena, they are not dependent on initial atmospheric conditions to the extent that weather forecast models are. Initial ocean conditions can affect the simulated climate over the course of several years (eg. El Nino/La Nina) to a decade or more.

For more information, see the COMET module Introduction to Statistics for Climatology.