Source: International Energy Association. IEA and IPCC (2014) Summary for Policymakers.
Several activity sectors contribute to the emission of greenhouse gases, with energy generation the most significant. Each source of carbon emission is the outcome of specific processes and technologies that cannot be collectively addressed. For instance, carbon emissions derived from electric power generation based on fossil fuels (coal or gas) cannot be mitigated in the same manner as carbon emissions related to the manufacturing of cement.
Transportation accounts for about 20% of greenhouse gas emissions, with road transportation accounting for three-quarters of this share. Aviation and maritime transportation account for 11%, respectively. Each of the main transportation modes requires its own mitigation strategy.