NATURAL AND ANTHAOPOGENIC RADIATIVE FORCING BASED ON IPCC AR5

Editor's Notes

• #3: to provide policymakers with regular assessments of the scientific basis of climate change, its impacts and future risks, and options for adaptation and mitigation.
• #11: 40% from natural sources Decaying vegetation, marsh gas. Agriculture, especially rice paddies with anaerobic bacteria. Ruminants (cattle and sheep) – you don’t want to know where it comes from! 500L cow-1 day-1 Termites (same chemistry)
• #14: Radiative forcing from aerosols has two competing components: a dominant cooling effect from most aerosols and their cloud adjustments and a partially offsetting warming contribution from black carbon absorption of solar radiation Changes in solar irradiance and volcanic aerosols cause natural radiative forcing. The radiative forcing from stratospheric volcanic aerosols can have a large cooling effect on the climate system for some years after major volcanic eruptions. Changes in total solar irradiance are calculated to have contributed only around 2% of the total radiative forcing in 2011, relative to 1750.
• #15: . Cumulative anthropogenic CO2 emissions of 2040 ± 310 GtCO2 were added to the atmosphere between 1750 and 2011. Since 1970, cumulative CO2 emissions from fossil fuel combustion, cement production and flaring have tripled, and cumulative CO2 emissions from forestry and other land use21(FOLU)22 have increased by about 40% (Figure 1.5)23. In 2011, annual CO2 emissions from fossil fuel combustion, cement production and flaring were 34.8 ± 2.9 GtCO2/yr. For 2002–2011, average annual emissions from FOLU were 3.3 ± 2.9 GtCO2/yr.
• #16: | Annual global anthropogenic carbon dioxide (CO2) emissions (gigatonne of CO2-equivalent per year, GtCO2/yr) from fossil fuel combustion, cement production and flaring, and forestry and other land use (FOLU), 1750–2011. Cumulative emissions and their uncertainties are shown as bars and whiskers, respectively, on the right-hand side. The global effects of the accumulation of methane (CH4) and nitrous oxide (N2O) emissions are shown in Figure 1.3. Greenhouse gas emission data from 1970 to 2010 are shown in Figure 1.6. {modified from WGI Figure TS.4 and WGIII Figure TS.2}
• #17: Total annual anthropogenic greenhouse gas (GHG) emissions (gigatonne of CO2-equivalent per year, GtCO2-eq/yr) for the period 1970 to 2010, by gases: CO2 from fossil fuel combustion and industrial processes; CO2 from Forestry and Other Land Use (FOLU); methane (CH4); nitrous oxide (N2O); fluorinated gases covered under the Kyoto Protocol (F-gases). Right hand side shows 2010 emissions, using alternatively CO2-equivalent emission weightings based on IPCC Second Assessment Report (SAR) and AR5 values. Unless otherwise stated, CO2-equivalent emissions in this report include the basket of Kyoto gases (CO2, CH4, N2O as well as F-gases) calculated based on 100-year Global Warming Potential (GWP100) values from the SAR (see Glossary). Using the most recent GWP100 values from the AR5 (right-hand bars) would result in higher total annual GHG emissions (52 GtCO2-eq/yr) from an increased contribution of methane, but does not change the long-term trend significantly. Other metric choices would change the contributions of different gases (see Box 3.2). The 2010 values are shown again broken down into their components with the associated uncertainties (90% confidence interval) indicated by the error bars. Global CO2 emissions from fossil fuel combustion are known with an 8% uncertainty margin (90% confidence interval). There are very large uncertainties (of the order of ±50%) attached to the CO2 emissions from FOLU. Uncertainty about the global emissions of CH4, N2O and the F-gases has been estimated at 20%, 60% and 20%, respectively. 2010 was the most recent year for which emission statistics on all gases as well as assessments of uncertainties were essentially complete at the time of data cut off for this report. The uncertainty estimates only account for uncertainty in emissions, not in the GWPs (as given in WGI 8.7). {WGIII Figure SPM.1}
• #20: Total anthropogenic greenhouse gas (GHG) emissions (gigatonne of CO2- equivalent per year, GtCO2-eq/yr) from economic sectors in 2010. The circle shows the shares of direct GHG emissions (in % of total anthropogenic GHG emissions) from five economic sectors in 2010. The pull-out shows how shares of indirect CO2 emissions (in % of total anthropogenic GHG emissions) from electricity and heat production are attributed to sectors of final energy use. ‘Other energy’ refers to all GHG emission sources in the energy sector as defined in WGIII Annex II, other than electricity and heat production {WGIII Annex II.9.1}. The emission data on agriculture, forestry and other land use (AFOLU) includes land-based CO2 emissions from forest fires, peat fires and peat decay that approximate to net CO2 flux from the sub-sectors of forestry and other land use (FOLU) as described in Chapter 11 of the WGIII report. Emissions are converted into CO2-equivalents based on 100-year Global Warming Potential (GWP100), taken from the IPCC Second Assessment Report (SAR). Sector definitions are provided in WGIII Annex II.9. {WGIII Figure SPM.2}