Near-surface temperatures

Isotopes of oxygen and hydrogen are useful tracers of water sources because they are constituents of the water molecule itself and because they are conservative in aquifers at near-surface temperatures. Isotopic techniques take advantage of the fact that lakes and their surrounding ground-water systems are usually isotopically distinct. Applications of stable isotopes for the study of lakes were first described by Dincer (10) and were discussed in several subsequent review articles (11-14). Most applications of isotopic techniques to lake systems are designed for the determination of water balances, nutrient-uptake studies, and paleotemperature reconstructions. 

Global Warming An increase in the near-surface temperature of the Earth. Global warming has occurred in the distant past as the result of natural influences, but the term is most often used to refer to a theory that warming occurs as a result of increased use of hydrocarbon fuels by man. See Climate Change (Greenhouse Effect). ... 

The success of core-top temperature calibrations indicates that physiological state, genetic variability, and depth and seasonality of production play secondary roles to the control on the sedimentary U37 index exerted by mean annual near-surface temperature. In most cases, these factors produce errors at the level of 1.5 °C or less in the global core-top calibration. To this observer s opinion, core-top data cannot be reconciled with the large variations in the U 7 index attributed to genetic or physiological factors by some culture studies. This does not indicate that the culture data are wrong in a technical sense, but that their results cannot always be extrapolated to the natural environment (Popp et al., 1998). 

One of the first comprehensive estimates of global mean, near-surface temperature over the earth s lands and oceans was reported in 1986 (Jones et al, 1986). The data showed a long-timescale warming trend. The three warmest years were 1980, 1981, and 1983, and five of the nine warmest years in the entire 124-year record up to 1984 were found to have occurred after 1978. It was apparent from this study that over this period, annual mean temperature increased by about 0.6 to 0.7°C, and that about 40 to 50% of this increase occurred since about 1975. According to many analysts, the warmest year on record up to 1995 is 1995, and recent years have been the warmest since 1860 despite the cooling effect of the volcanic eruption of Mt. Pinatubo in 1991... 

FIGURE 4 Indiviclvial impulse-response functions for the carbon cycle (response R. of the atmospheric COt concentration to a 5-function COi input at time t = 0, left) and the variables global mean near-surface temperature (center) and mean sea-level rise (right) for the physical ocean-atmosphere sy stem (response to a step-function increase in the CO2 concentration to a constant level at time t = 0). The units for temperature response Rj and sea-level response R< refer to the amplitudes of the first empirical orthogonal functions (EOFs) of the response patterns of the respective variables and are essentially arbitrary (see text). Adopted from Hooss ft /., 2001. 

FIGURE 6 Dominant spatial-response pattern (first EOF) of near-surface temperature change to increased atmospheric CO2 concentration (from Hooss et al., 2001). See also color insert. 

FIGURE 10 Optimized CO, emission paths with resulting changes in CO, concentration and global mean near-surface temperature. S( baseline scenario discounting of abatement costs only, finite economic inertia same as baseline scenario without economic inertia S, same as baseline scenario but with equal discounting of climate damages and abatement costs. 

Figure 1.8 (a) Global near-surface temperature averaged over land and ocean,... 

Variations in water content in soils and rocks that may not be readily apparent on black and white photographs often are depicted by false colour. In fact, the specific heat of water is usuaiiy two to ten times greater than that of most rocks, and this, therefore, facilitates its detection in the ground. Indeed, the specific heat of water can cause an aquifer to act as a heat sink that, in turn, influences near-surface temperatures. 

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