Northern-Hemisphere

Air. Studies have shown that 2500 years ago lead pollution caused by Greek and Roman silver smelters was a significant problem (4). Based on analysis of lake sediments and Greenland s ice, it was found that lead contamination from smelters in southern and central Europe was carried throughout the northern hemisphere. As long ago as the thirteenth century, air pollution has been linked to the burning of coal (4). The main concern was the smell from the sulfur in the coal and the effects of the soot. It was not until many years later that the effects of air pollution on people s health were discovered. 

Fig. 11-1. Mean monthly concentrations of atmospheric C02at Mauna Loa. The yearly oscillation is explained mainly by the annual cycle of photosynthesis and respiration of plants in the Northern Hemisphere. Source Lindzen (2).

In the friction layer where the isobars are curved, the effect of frictional drag is added to the forces discussed under gradient wind. The balance of the pressure gradient force, the coriolis deviating force, the centrifugal force, and the frictional drag in the vicinity of the curved isobars results in wind flow around low pressure and high pressure in the Northern Hemisphere, as shown in Fig. 17-16. 

Scientists have been able to compare the seasonal changes in atmospheric carbon dioxide to the seasonal changes in photosynthesis in the Northern Hemisphere. Plants take up more carbon dioxide in... 

Coal is the most abundant and most economical fossil fuel resource in the world. Proven coal reseiwes exceed 1 trillion tons, and indicated reserves are estimated at 24 trillion tons. Coal is found in eveiy continent of the world, including Antarctica, although the largest quantities of coal are in the Northern Hemisphere. Coal is mined in some sixty countries in nineteen coal basins around the world, but more than 57 percent of the world s total recoverable reserves are estimated to be in the United States, and China, which together account for more than two-thirds of the world s coal production. 

The major source of plutonium in natural waters is the atmospheric fallout from nuclear weapons tests. Fallout plutonium is ubiquitous in marine and freshwater environments of the world with higher concentrations in the northern hemisphere where the bulk of nuclear weapons testing occurred(3). Much of the research on the aquatic chemistry of plutonium takes place in marine and freshwater systems where only fallout is present. 

Table IV. Predicted HO concentrations near the surface of the Northern Hemisphere. Average values obtained from tropospheric models. Taken from Altshuller (147) (see that paper for table references 20 and 24).

Sulfur dioxide Is formed primarily from the Industrial and domestic combustion of fossil fuels. On a global scale, man-made emissions of SOj are currently estimated to be 160-180 million tons per year. These emissions slightly exceed natural emissions, largely from volcanic sources. The northern hemisphere accounts for approximately 90% of the man-made emissions (13-14). Over the past few decades global SOj emissions have risen by approximately 4%/year corresponding to the Increase In world energy consumption. 

Several studies, based on models, examined the effects of land-use change on the global carbon cycle and conclude that there is a net release of carbon due to land clearing. However, the results and conclusions of these studies are based on assumed sizes of vegetation carbon pools which are inputs to the models. For example, Melillo et al. 24) concluded that boreal and temperate deciduous forests of the northern hemisphere are net sources of atmospheric carbon. Their analysis used values for carbon density derived by Whittaker and Likens 19) from work by Rodin and Bazilevich (27). Rodin and Bazilevich extrapolated results of small, unrelated studies in Europe and the USSR to estimate total biomass of Eurasian boreal and temperate deciduous forests. Their estimates have since been extrapolated to forests worldwide and are used often today. 

Fig. 7-4 Cross-section of the northern hemisphere atmosphere showing first-order circulation. The southern hemisphere is a mirror image.

This describes the geostrophic wind f- 2co sin 4>, where oj is the angular velocity due to the rotation of the Earth and 0 is the latitude). The air moves parallel to the isobars (lines of constant pressure). The geostrophic wind blows counterclockwise around low-pressure systems in the northern hemisphere, clockwise in the southern. 

The area, volume and average depth of the ocean basins and some marginal seas are given in Table 10-1. The Pacific Ocean is the largest and contains more than one-half of the Earth s water. It also receives the least river water per area of the major oceans (Table 10-2). Paradoxically it is also the least salty (Table 10-3). The land area of the entire Earth is strongly skewed toward the northern hemisphere. 

As a result of these factors (wind, Ekman transport, Coriolis force) the surface ocean circulation in the mid-latitudes is characterized by clockwise gyres in the northern hemisphere and the counterclockwise gyres in the southern hemisphere. The main surface currents around these gyres for the world s oceans are shown in Fig. 10-6. The regions where Ekman transport tends to push water together are called convergences. Divergences result when surface waters are pushed apart. 

The atmospheric CO2 content increased by about 1 ppmv per year during the period 1959-1978 (Bacastow and Keeling, 1981) with the South Pole Pco increase lagging somewhat behind the Mauna Loa (19.5°N,155.6 "W) data. This difference is consistent with our knowledge of interhemispheric mixing times and the fact that most fossil fuel emissions occur in the northern hemisphere (see also Conway et al, 1994a). 

Fig. 11-26 Decade-averaged data of Northern hemisphere tree ring records from 1750-1979 and 7th-degree polynomial fit of the data. The vertical extension of blocks represents 95% confidence limits of the mean. The open circles give the change of —0.65% in atmospheric CO2 observed from 1956 to 1978 by Keeling et al. (1979). (Adapted from Peng et al, 1983.)...

Bolin, B. and Bischof, W. (1970). Variations of the carbon dioxide content of the atmosphere in the northern hemisphere, Tellus 22,431-442. 

Ereyer, H. D. and Belacy, N. (1983). C/ C records in Northern Hemispheric trees during the past 500 years - anthropogenic impact and climatic superpositions, /. Geophys. Res. 88, 6844-6852. 

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