Global Warming and CO2 Emissions
CO2 continued an upward trend in the early years of the 21st century. Fossil fuels are the dominant form of energy utilized in the world (86%), and account for about 75% of current anthropogenic CO2 emissions (IPCC, 2001c). In 2002, 149 Exajoules (EJ) of oil, 91 EJ of natural gas, and 101 EJ of coal were consumed by the world’s economies (IEA, 2004).
Global primary energy consumption grew at an average rate of 1.4% annually between 1990 and 1995 (1.6% per year between 1995 and 2001); the growth rates were 0.3% per year (0.9%) in the industrial sector, 2.1% per year (2.2%) in the transportation sector, 2.7% per year (2.1%) in the buildings sector, and –2.4% per year (–0.8%) in the agricultural/other sector (IEA, 2003).
Average global CO2 emissions increased by 1.0% per year between 1990 and 1995 (1.4% between 1995 and 2001), a rate slightly below that of energy consumption in both periods. In individual sectors, there was no increase in emissions from industry between 1990 and 1995 (0.9% per year from 1995 to 2001); there was an increase of 1.7% per year (2.0%) in the transport sector, 2.3% per year (2.0%) in the buildings sector, and a fall of 2.8% per year (1.0%) in the agricultural/other sector (IEA, 2003).
Total emissions from fossil fuel consumption and flaring of natural gas were 24 GtCO2 per year (6.6 GtC per year) in 2001 – industrialized countries were responsible for 47% of energy-related CO2 emissions (not including international bunkers ). The Economies in Transition accounted for 13% of 2001 emissions; emissions from those countries have been declining at an annual rate of 3.3% per year since 1990. Developing countries in the Asia-Pacific region emitted 25% of the global total of CO2; the rest of the developing countries accounted for 13% of the total (IEA, 2003).
Anthropogenic climate change is mainly driven by emissions of CO2 but other greenhouse gases (GHGs) also play a part . Since some of the anthropogenic CO2 comes from industrial processes and some from land use changes (mainly deforestation), the contribution from fossil fuel combustion alone is about half of the total from all GHGs. In terms of impact on radiative forcing, methane is the next most important anthropogenic greenhouse gas after CO2 (currently accounting for 20% of the total impact) (IPCC, 2001b). The energy sector is an important source of methane but agriculture and domestic waste disposal contribute more to the global total (IPCC, 2001c). Nitrous oxide contributes directly to climate change (currently 6% of the total impact of all GHGs); the main source is agriculture but another is the industrial production of some chemicals; other oxides of nitrogen have an indirect effect. A number of other gases make significant contributions (IPCC, 2001c). Avoiding severe global climate change is an enormous challenge. Greatly reducing man-made carbon dioxide (CO2) emissions is central to meeting that challenge. The Intergovernmental Panel on Climate Change (IPCC) estimates that CO2 emissions must be reduced 50 to 85 percent by 2050 compared to 2000 levels. That reduction will keep the global mean temperature rise below 2.0 to 2.4oC, where severe impacts begin. Yet, the trend in global CO2 emissions is a continued rapid rise for the foreseeable future. To date, industrialized countries have emitted most of the CO2. Emissions from developing countries ,however, are growing much faster and their emissions will overtake those of the industrialized countries in the near future.
Adequately reducing CO2 emissions will require global efforts in virtually every economic sector—power, industry, fuel transformation, transport, and buildings—in both industrialized, transitional and developing economies. Human activity globally currently releases about 28 gigatonnes of CO2 (GtCO2) per year into the atmosphere. Cutting this in half or more would bring emissions to 14 GtCO2 or below by 2050. This is a reduction of at least 48 GtCO2 below the 62 GtCO2 projected for 2050 under current trends. Cumulatively, at least about 600 Gt will have to be cut over the entire period.
Many different measures are necessary to reduce greenhouse gas emissions. These measures include increasing energy efficiency in all sectors; using renewable energy sources such as wind, biomass, geothermal and solar energy; switching to low- or no-carbon fuels; and implementing carbon dioxide capture and storage. It is also necessary to reduce emissions of other greenhouse gases such as methane and nitrous oxide and to enhance natural sinks for CO2 such as rainforests.