1. Calculation of total carbon emissions
It is mainly a comprehensive measurement of carbon emissions represented by the National Greenhouse Gas Inventory of the Intergovernmental Panel on Appearance Change (IPCC). In the 2006 National Greenhouse Gas Emissions, IPCC’s comprehensive measurement of carbon emissions includes four aspects: energy, industrial process and product use, agriculture, forestry and other land use, and waste, involving three methodological layers. The idea is to combine information about the extent of human activity with coefficients that quantify emissions or removals per unit of activity. The information on the occurrence degree of human activities is called activity data, which is represented by AD; the coefficient is called emission factor, which is represented by EF. Therefore, the basic equation for the calculation is:
Among them, COE is the total carbon emission, AD is the activity data, and EF is the emission factor.
Taking the energy sector as an example, its activity data is the amount of fossil energy combustion, and the emission factor is the amount of carbon dioxide emitted per unit of fossil energy combustion. In the energy sector, carbon dioxide becomes the main emission gas, accounting for 95% of the total carbon emissions in the energy sector. For CO2, the emission factor mainly depends on the carbon content of the fuel, the combustion conditions (combustion efficiency, carbon residues in slag, ash, etc.) are relatively unimportant. Therefore, CO2 emissions from the energy sector can be estimated fairly accurately based on the total amount of fuel burned and the average carbon content in the fuel.
This measurement method is generally used to measure the overall carbon emissions of a country, and it is the net carbon emissions after deducting the impact of carbon sinks. The purpose is to enable the carbon emissions of various countries to be measured according to a unified method to report to the United Nations Framework Convention on Climate Change, and to facilitate the United Nations to monitor and compare the emission reductions and emission reduction effects of various countries in real time. Although this method is simple, the guarantee of accuracy requires a large amount of detailed data. For scholars with different research purposes, they will measure a country’s local carbon emissions while considering the cost.
2. Classification according to the idea of emission reduction
(1) Top-down approach
The top-down method is to measure carbon emissions from various elements of the macro economy, and it is an aggregate model describing the entire economy, including various elements of the entire macro economy. In the estimation of carbon emissions from carbon sources, the input-output 10 model and the econometric model are mainly used.
(2) Bottom-up method
In contrast to the top-down approach, the bottom-up approach is a model based on detailed technical information. After modeling energy optimization, technical performance, and abatement costs, estimate the amount of greenhouse gas emissions under the conditions of different energy use structures and technology applications. The AMI-LOCAL/China model used by Yang Hongwei in studying the environmental benefits of emission reduction technologies falls into this category. Earlier models of this type focused on how to meet energy demand at the lowest cost, but more recent developments allow demand to respond to energy prices.
3. Mixed models
A mixed model is a mixed model composed of two types of top-down and bottom-up models. Whether it is a top-down model or a bottom-up model, the differences in the simulation results are caused by the differences in the structure of the model, the basis of economic theory, and key assumptions. An in-depth discussion was conducted by Wilosn et al. after systematically comparing the differences between the two. Some economists argue that a combination of the two approaches should be used because they are complementary rather than substitutive relationships in most cases (Bohring, 1998).
The hybrid model can analyze both top-down policies such as carbon tax and bottom-up policies such as power plant technical specifications and emission reduction costs. GLOBAL (Manne, 1992), NEMS (Kdyes, 1999) models are all representatives of mixed models.