California Climate Change Glossary

Letter L

Land Use. The management practice of a certain land cover type (a set of human actions). Land use may be forest, arable land, grassland, urban area or other. (Lenn)

Land Use Change. Alteration of the management practice on a certain land cover type. Land use changes may influence the climate system because they impact evapotranspiration and sources and sinks of greenhouse gases. (Lenn)

Lifetime (Atmospheric). The lifetime of a greenhouse gas refers to the approximate amount of time it would take for the anthropogenic increment to an atmospheric pollutant concentration to return to its natural level (assuming emissions cease) as a result of either being converted to another chemical compound or being taken out of the atmosphere via a sink. This time depends on the pollutant's sources and sinks as well as its reactivity. The lifetime of a pollutant is often considered in conjunction with the mixing of pollutants in the atmosphere; a long lifetime will allow the pollutant to mix throughout the atmosphere. Average lifetimes can vary from about a week (sulfate aerosols) to more than a century (CFCs, carbon dioxide).

Lithosphere. The outer part of the earth, consisting of the crust and upper mantle, approximately 100 km thick. (Lenn)

LULUCF. Acronym for Land Use, Land Use Change and Forestry activities, all designed to increase carbon stores, or sinks, and so make sequestration easier. (BBC)