Vegetation affects climate in two main ways: first, it affects the albedo of a region, or the amount of incoming radiation that is reflected back from a given surface. For example, in the Arctic there are two main types of vegetation cover, forest and tundra. When snow falls on the low-lying tundra it covers the vegetation and reflects sunlight; when snow falls on forest trees it is usually blown away, and rather than being reflected back into space, incoming sunlight is absorbed by the snowless trees.
The second way vegetation affects climate is by changing the concentrations of gases in the atmosphere. This is particularly important, and well understood, for C02:
The second way vegetation affects climate is by changing the concentrations of gases in the atmosphere. This is particularly important, and well understood, for C02:
Two trends are obvious in this graph. First, the data generally move in an upward direction over time, indicating that the concentration of CO2 in the atmosphere has increased steadily since at least 1960. Second, there are also much smaller oscillations that have a cycle of one year, shown in red and in the lower right inset. These regular, smaller-scale ups and downs in global CO2 concentration correspond with the seasons in the Northern hemisphere, where most of the Earth’s vegetative biomass is located. In the spring and summer (May-August) in the Northern hemisphere, new leaves emerge on plants which begin taking in CO2 for photosynthesis, and the atmospheric CO2 concentration drops. Then in autumn and winter when leaves fall, CO2 is released back into the atmosphere, drawing the curve back upward.
The overall upward trend of the graph is also influenced by deforestation, or clearing land of vegetation, which results in less biomass available for CO2 uptake.
The overall upward trend of the graph is also influenced by deforestation, or clearing land of vegetation, which results in less biomass available for CO2 uptake.