California Climate Change Glossary

Letter D

Damage Function. The relation between changes in the climate and reductions in economic activity relative to the rate that would be possible in an unaltered climate. (IPCC)

Deforestation. Those practices or processes that result in the change of forested lands to non-forest uses. This is often cited as one of the major causes of the enhanced greenhouse effect for two reasons: 1) the burning or decomposition of the wood releases carbon dioxide; and 2) trees that once removed carbon dioxide from the atmosphere in the process of photosynthesis are no longer present and contributing to carbon storage. (EPA)

Desertification. The progressive destruction or degradation of existing vegetative cover to form desert. This can occur due to overgrazing, deforestation, drought, and the burning of extensive areas. Once formed, deserts can only support a sparse range of vegetation. Climatic effects associated with this phenomenon include increased albedo, reduced atmospheric humidity, and greater atmospheric dust (aerosol) loading. (EPA)

Detection of Cliamte Change. The process of demonstrating that climate has changed in some defined statistical sense, without providing a reason for that change. (Lenn)

Discount rate. The annual rate at which the effect of future events are reduced so as to be comparable to the effect of present events. (IPCC)

Diurnal Temperature Range. The difference between maximum and minimum temperature over a period of 24 hours. (IPCC)

Dobson Unit (DU). This unit measures the total amount of ozone in a vertical column above the earth. One DU corresponds to a column of ozone containing 2.69 x 10²⁰ molecules per square meter. The number of Dobson Units is the thickness in units of 10-5 m, that the ozone column would occupy if compressed into a layer of uniform density at a pressure of 1013 hPa, and a temperature of 0°C. (Lenn)

Driving Forces. Climate scenarios contain various driving forces of climate change, including population growth and socio-economic and technological development. These drivers encompass various future scenarios that might influence greenhouse gas sources and sinks, such as the energy system and land use change. (Lenn)