From these measurements, they calculate the concentration of ozone in the atmosphere above that location. These data, although useful in learninmg about ozone, are not able to provide an adequate picture of global ozone concentrations. Ozone molecules drift and swirl around the stratosphere in changing concentrations - such as clouds do in the satellite weather pictures seen on television news. Therefore, scientists observing ozone fluctuations over just one spot could not be confident that a change in local ozone levels meant an alteration in global ozone levels, or simply a fluctuation in the concentration over that particular spot. Satellites have given scientists the ability to overcome this problem because they provide a picture of what is happening simultaneously over the entire Earth.
Scientists now are confident that ozone is being depleted workwide - partly due to human activities.
However, scientists still need to determine how much of the loss is the result of human activity, and how much is the result of fluctuations in natural cycles.