CO2 AND CLIMATIC-CHANGE - AN OVERVIEW OF THE SCIENCE

International policy measures to deal with the enhanced greenhouse eff ect am being debated on a scientific basis which is still uncertain. T he Intergovernmental Panel on Climate Change (IPCC) has produced a maj or scientific assessment of climatic change. They concluded that, desp ite uncertainties, the model simulations of a warming due to increased concentrations of greenhouse gases am broadly consistent with observa tions of global temperature changes. Carbon dioxide is the most import ant greenhouse gas from human activities. Increases in CO2 concentrati ons in the atmosphere contribute over half of the enhanced greenhouse effect, the rest being mainly due to increases in halocarbons and meth ane. The total effect of greenhouse gas emissions depends on their lif etimes in the atmosphere. The global warming potential of other greenh ouse gases is expressed relative to that of CO2. However, the lifetime Of CO2 in the atmosphere is complicated by uptake into the many carbo n storage sinks of the global carbon cycle. Knowledge of the global ca rbon cycle is incomplete, the sources exceeding the sum of known sinks . Reductions in the concentration of CO2 in the atmosphere could be ac hieved by reducing the emissions or enlarging the sinks. What is achie ved in future will depend to a large extent on a mom detailed understa nding of carbon storage mechanisms.