Search

Top-down and bottom-up modelling techniques have been used to answer the question of how much would it cost to reduce greenhouse gas emissions. These two types of models, however, were conceived and designed through different disciplines, for different purposes and lead to very different conclusions. Recent attempts to compare the two modelling approaches illustrate the difficulty in reconciling their results. In this paper, both modelling techniques are described and discussed, and the gap between their results is explored.

An integrated approach for choosing among energy supply- and demand-side measures shows that, compared to business-as-usual demand patterns, global greenhouse-gas emissions can be reduced well below current levels with net economic benefits to society. Given these findings, a ‘wait-and-see’ stance towards new initiatives in energy and environmental policy is not economically justifiable. Achieving signifincant emissions reductions, however, will require commitments to policies aimed at enabling energy markets to function more efficiently and supporting legislation where market forces do not suffice.

Greenhouse forcings from natural gas, coal and oil consumption are compared. Carbon dioxide, methane and nitrous oxide emissions are addressed using a complete fuel-cycle approach. The near- and long-term CO2-equivalent forcings resulting from consuming one MJ of each fuel are presented. Compared on that basis, naturalgas exploitation is less offensive than either coal or oil exploitation in both time-frames. The greenhouse forcing caused by fossil-fuel based electricity/heat systems using a variety of technologies is compared on a per kWhe basis.