The clock shows the growth of the world population. The incidence of malnutrition in the population and the incidence of HIV infection and cancer.
The clock shows the rising earth's temperature and emmissions of carbon dioxide (CO2) indictating the earth's relentless path to global warming.
It shows the number of species becoming extinct as time ticks by. You can compare the amount of forest lost against the amount of forest replanted and the amount of land turning into dessert (desertification).
There is a prediction as to when the oil will run out with the depletion timer - the Earth's oil reserves are falling every second. The polution by oil in ours seas is shown in tons.
The clock shows the continued build up of nuclear waste.
It shows the amount of waste in the US which can be compared to the amount recylced.