Historical levels

Historically, U.S. pulp and paper companies have invested heavily in capital improvements to their facilities. Capital investments in recent years, however, are well below historic levels due to the difficult market conditions. For the first time, industry capacity actually declined in 2001.1 2 3 Because few new mills are being built, most capital expenditures are for plant expansions, upgrades, and environmental protection initiatives at existing facilities. Throughout the time period 1985-1999, capital improvements related to environmental protection claimed from 4% to 22% of the total investments, with significant increases in the early and late 1990s.1... 

In remote reservoirs not affected by anthropogenic pollution, particle trapping can reduce the available nutrients. In the Canadian Rocky Mountains, fertihzer has been added to lakes and rivers in the form of liquid ammonium polyphosphate with the goal to stabihze nutrient concentration at historical levels [5]. 

While not a true hole in the sense that some column ozone remains even in the most extreme depletions observed in the mid 1990s (when October ozone minima were near 100 Dobson Units over the South Pole, or depletion of about two-thirds of the historical levels, see Hofmann et al, 1997), the descriptor captures the fact that the peak depletion is sharply limited to Antarctic latitudes. Dobson (1968 and references therein) noted that there is less ozone naturally present over Antarctica than over the Arctic in winter and much of the spring, but this climatological difference between the natural ozone levels over the poles of the two hemispheres should not be confused with the abrupt decline that began near the mid-1970s as depicted in Figure 6.9. Newman (1994) discusses these and other historical measurements of total ozone and shows that the Antarctic ozone hole began only in the last few decades. 

Figure 6.11 shows measurements of the seasonal cycle of ozone at Halley in historical and recent data, which show that the depletion occurs only over a limited portion of the year. These observations demonstrate that contemporary observations of ozone at Halley in late August (end of austral winter) are near historical levels, while the bulk of the ozone loss there occurs rapidly during the month of September. In recent years, measurable ozone depletion is also observed in Antarctic summer — in part the result of dilution of the extreme losses in spring. 

In the previous chapter we numerically simulated employer and worker safety incentives and workers decisions to file WC claims. In our simulations doubling the WC income replacement rate from its recent historical level would reduce the injury rate by two percent while raising reported injuries by about 30 percent. Our numerical simulations illustrated that when WC benefits increase the actual rate of work-related injuries can fall while the application rate for workers compensation benefits rises. 

When people talk about the Greenhouse Effect , what they are referring to is something extra the effect on the Earth s temperature caused by carbon dioxide concentrations rising above the historic level. Before the Industrial Revolution, the COj level was around 280 ppm, 0.028% of the atmosphere. Daily average CO2 levels (measured at Mauna Loa Observatory in Hawaii) have increased from around 310 ppm (0.031%) in 1958 to 400 ppm (0.040%), first reached on May 9th 2013. 

As the world has become accustomed to sulfur at a penny a pound, the pivotal question is can a source be found to keep the price at this historical level for the remainder of the present century, or even the next ... 

As with Portland cement mortars, there is a potential detrimental effect of incorporating finely ground pigments at excessive levels. While there are no specific guidelines for maximum pigment addition levels to natural cement mortars, their proper historic levels of use were described by Gillmore as moderate. Current ASTM C 979 restrictions of <2 % carbon black and <10 % iron oxide on cement weight (for Portland cement colorants) probably represent prudent limits. 

Expected fatalities - per hour, per year, or per individual - of various exposed groups were estimated from post-data and then compared to assessments of the benefits accruing from these activities. Starr (1969) found that historical levels of risk acceptance increased in proportion to the cube root of the increase in benefits. Voluntary acceptance levels were about three orders of magnitude greater than involuntary acceptance levels. 

Fig. 1.2 (A) CO2 concentrations in the atmosphere measured at Manua Loa (Wikipedia-Contiibutors 2007a) (B) temperatures reiative to historic levels (Wikipedia-Contiibutors 2007b).

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