key concept 53.2 Global Climate Is a Fundamental Component of the Physical Environment

The terms “weather” and “climate” both refer to atmospheric conditions—temperature, humidity, precipitation, and wind direction and velocity—but they consider different time scales. Weather is the short-term state of atmospheric conditions at a particular place and time, whereas climate refers to the average atmospheric conditions, and the extent of their variation, at a particular place over a longer time (years to millennia).

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  • “Weather” and “climate” refer to atmospheric conditions at different time scales.

  • Earth’s spherical shape creates latitudinal variation in solar radiation absorption and thus differences in temperature and precipitation; the proportion of land to ocean is also important.

  • Earth’s rotation around its axis deflects air and water and creates prevailing winds and ocean currents.

  • The tilt of Earth’s axis and its orbit create seasons.

Climate is what you expect given past conditions; weather is what you get on any one day. For example, a warming climate will cause glaciers to melt over decades or centuries (see Figure 1.16), whereas a single large snowstorm is unlikely to thwart that retreat. In addition, the responses of organisms to weather are usually short-term—seeking shelter from a sudden rainstorm, for example, or shivering to keep warm when the temperature drops. Climate, by contrast, acts as a sort of filter for organisms, ultimately determining their distribution and abundance. If organisms cannot tolerate the climate of a particular place, they will not be found there. What are the processes that create global climate patterns?