Carbon leakage occurs when there is an increase in greenhouse gas emissions in one country as a result of an emissions reduction by a second country with a strict climate policy. Carbon leakage may occur for a number of reasons: There is no consensus over the magnitude of long-term leakage effects. This is important for the problem of climate change. Carbon leakage is one type of spill-over effect. Spill-over effects can be positive or negative; for example, emission reductions policy might lead to technological developments that aid reductions outside of the policy area.