Pre-industrial period

Fig. 17-6 Calculated geographical distribution of the climate forcing (W/m ) by anthropogenic greenhouse gases alone, from pre-industrial periods to ca. 1990. From IPCC (1995), after Kiehl and Briegleb (1993). See text for interpretation. (Reprinted by permission from IPCC.)...

The atmospheric burden of anthropogenic CO2 is very well known because it has been measured since 1958 and recent ice core studies indicate how the atmospheric CO2 evolved between the pre-industrial period and 1958 (Fig. 11.3). Because industries and governments keep records of the amount of fossil fuel recovered, this number is also known. The amount of atmospheric CO2 increase over the period 1860-1989 is estimated to be only 40% of total emissions (Table 11.1). Where has the rest gone ... 

Although it is accepted that atmospheric mercury burdens have increased substantially since the pre-industrial period, it is uncertain whether overall atmospheric mercury levels are currently increasing, decreasing, or remaining stable. Measurements of mercury over remote areas of the Atlantic Ocean show increasing levels up until 1990 and a decrease for the period 1990-1994 (Slemr 1996, Pirrone et al. 2000, Munthe et al. 2001). However, other measurements at remote sites in northern Canada and Alaska show deposition rates... 

Fig. 1.6 Calculated zonal and 24-h average OH concentrations in units of 10 molecules/cm for the pre-industrial period for January, April, July and October...

Cenozoic is a time of high but variable pCOj. By early Miocene time (ca. 22 Ma) COj levels are comparable to the present (pre-industrial) values. The calculated pCOj for the period from the middle Miocene through the Pliocene comes out lower than the modem value, which does not correspond well with the 5 0 evidence for continued cooling between 15 Ma and the present (Fig. 16c). It may be noteworthy that higher assumed values for 5 correspond to very high levels of atmospheric COj in the early Cenozoic, whereas 5w values in the range -0.5 to -0.6 correspond to the lx to lOx higher COj levels that are typically estimated with other approaches (e.g., Ekart et al. 1999). 

The Maunder minimum is the name given to a period of extreme solar inactivity that occurred between 1645 and 1710. Of particular interest is that this period of inactivity corresponds closely to one of the coldest periods of the so-called Little Ice Age in Europe, a time of long, cold winters that caused severe hardships in the pre-industrial revolution world. This has led scientists to extensively study the possible influences of solar activity on terrestrial climate, as well as examine other stars for evidence of activity cycle behavior similar to the Sun s. 

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