In 1975 there was little development along the roads. By 1986 many secondary roads had been built. Areas where the forest has been cut down for lumber or crops extend out from the secondary roads in blue feather-like patterns. This graph presents data gathered on Mauna Loa, a volcano 4,000 meters high in Hawaii. Two patterns can be seen.
Plants draw carbon dioxide from the atmosphere to make food.
Thus, in the Northern hemisphere CO2 concentration peaks in early spring just before plant growth begins and falls off in October when the growing season ends. Trees record climate change. Each year a tree forms a new layer of tissue. The width of each year's ring reflects growing conditions such as moisture or sunlight.