But the strength of the greenhouse effect depends on the chemical composition of the atmosphere, because the phenomenon is due to the absorption of infra-red radiation by various gases in the air.
Mr Freeman finds that, in practice, employment-protection laws appear to have little effect on the overall level (as opposed to the composition) of employment.
To date, no drug has been approved in its leaf form because plants contain a complex composition of compounds with uncertain pharmacologies, metabolisms, side-effect profiles, toxicologies, drug interactions, and no control of relative concentrations.