38
present, instrument data from HadCRUT.4.4.0.0 (Jones et al. 2012 ) was used. Both
datasets were downloaded from the websites described for Fig. 1.1. A 21-year run-
ning mean was used to smooth HadCRUT.4.4.0.0 record up to 2008; data from 2009
to 2015 represent unsmoothed annual averages.
The GHG data in Fig. 1.2 is based on three data records. For 0 AD to 1764,
observations of CO 2 , CH 4 , and N 2 O are based on the Law Dome Ice Core (MacFarling
Meure et al. 2006 ) archived by NOAA NECI at:
http://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/law/law2006.txt
For 1765 to modern times (1979 for CO 2 ; 1983 for CH 4 , 1977 for N 2 O), GHG abun-
dances are based on the RCP 4.5 archive at:
http://www.pik-potsdam.de/~mmalte/rcps/data/RCP45MIDYEAR
CONCENTRATIONS.DAT
For years since 1980 for CO 2 , 1984 for CH 4 , and 1978 for N 2 O, GHG abundances
are based on observations provided by NOAA ESRL (Ballantyne et al. 2012 ;
Dlugokencky et al. 2009 ; Montzka et al. 2011 ) at:
ftp://aftp.cmdl.noaa.gov/products/trends/co2/co2_annmean_gl.txt
ftp://aftp.cmdl.noaa.gov/products/trends/ch4/ch4_annmean_gl.txt
ftp://ftp.cmdl.noaa.gov/hats/n2o/combined/HATS_global_N2O.txt
Population data in Fig. 1.2, for years up to and including 1950, are from the History
Database of the Global Environment (HYDE) of the Netherlands Environmental
Assessment Agency (Klein Goldewijk et al. 2010 ). For 1951 to present, population
data from the Department of Economic and Social Affairs of the United Nations
(United Nations 2015 ) have been used. The population databases are maintained at:
http://themasites.pbl.nl/tridion/en/themasites/hyde/index.html
http://esa.un.org/unpd/wpp/Download/Standard/Population
Figure 1.3 shows values of RF forcing of climate, relative to year 1765, for the
RCP 4.5 scenario (Meinshausen et al. 2011 ) from file:
http://www.pik-potsdam.de/~mmalte/rcps/data/RCP45MIDYEAR
RADFORCING.DAT
maintained at the Potsdam Institute for Climate Research. The Anthropogenic
Aerosols terms includes the direct radiative effect of aerosols, the perturbation to
the reflectivity of clouds induced by aerosols, and the darkening of snow caused by
the deposition of black carbon. The following types of aerosols were considered:
sulfate, organic carbon and black carbon from both fossil fuel combustion and bio-
mass burning, nitrate, and mineral dust. The total anthropogenic term combines the
contributions to RF of climate from all GHGs released by human activity, plus RF
of climate due to aerosols, depletion of stratospheric O 3 , the increase of tropospheric
O 3 , and rising surface reflectivity due to land use change. Figure 1.3 also shows the
global mean surface temperature anomaly (ΔT) relative to pre-industrial (1850–
1900) baseline. Data sources for ΔT are the same as for Fig. 1.2.
Figure 1.4 shows the change in the radiative forcing (ΔRF) over the course of
the Anthropocene (in this case, 1750–2011) from Chap. 8 of IPCC ( 2013 ). Numerical
estimates for ΔRF are shown when available; otherwise, numerical estimates for the
change in Effective Radiative Forcing (ΔERF) are used. Effective Radiative Forcing
(ERF) is a new concept introduced in IPCC ( 2013 ), based on model simulations that
1 Earth’s Climate System