Northern hemisphere , temperature

Hurrel, J. W., 1996. Influence of variations in extratropical wintertime teleconnections on the Northern Hemispheric temperature. Geophysical Research Letters, 23, 665-668. 

I will discuss this in more detail using some recent climate simulation experiments (Roeckner et al., 1999 Bengtsson et al., 1999) as tools in such an evaluation. However, first I will discuss the possible mechanisms responsible for the variation of the Northern Hemisphere temperature. 

FIGURE 3 Simulated Northern Hemisphere temperature varations for 300 years with the ECHAM4/OPYC3 coupled climate model. Annually averaged and 50-year low-pass filter. 

Mann, M., Bradley, R., and Hughes, M. (1999). Northern hemisphere temperatures during the post millenium inferences, uncertainties, and limitations. Geophys. Res. Lett. 26,759-762. 

Mann, M.E., R.S. Bradley, and M.K. Hughes. (1999). Northern Hemisphere Temperatures During the Last Millennium Inferences, Uncertainties and Limitations. Geophysical Research Letters, 26, 759-762. 

The last decade has seen a dramatic improvement in both availability of past evidence and also in information from diverse regions and sources. Figure 8 compares several different reconstructions of Northern Hemisphere temperature change for most of the last millennium. The reconstructions are of different seasons so, based on the instrumental record, would be expected to differ somewhat. None of the series is strictly independent of the others, as they contain some common sources, but each has made different assumptions in averaging. 

Lauritzen, S.-E. (2005) Highly variable northern hemisphere temperatures reconstructed from low- and high-resolution proxy data. Nature, 433, 613-617. 

Mayewski, P. A., Meeker, L. D., Twickler, M. S. et al. (1993). Ice core sulphate from three northern hemisphere sites Source and temperature forcing implications. Atmos. Environ. A 27(17/18), 2915-2919. 

In the individual compartments quasi-steady state is achieved depending on emissions, degradation rates and spatial distribution of DDT. According to the seasonality of the parameters affecting degradation rates, e.g. temperature and oxidant abundance, the compartmental burdens in steady state follow a seasonal cycle. As the sources and consequently most of the DDT mass is located in the northern hemisphere, the cycle is defined by the climate of that hemisphere. Times needed to to achieve quasi staty state in the compartments are equal in the AGG and SAT experiment, as well as amplitude and phase of the burden time series. Vegetation reaches quasi-steady state within 2-4 years, and atmosphere already within 2 years. These... 

The RGB composite of the coefficients of determination of the individual linear correlation coefficients (Figure 2.26) shows that for the northern hemisphere high correlations of volatilisation rate and wind speed in the Atlantic Ocean can be found in the Gulf Stream and low values in the Labrador Sea and the adjacent Davis Strait. High correlations with the sea surface temperature are located near 45 °N close to the eastern coast of the American continent, in the Baltic Sea, North Sea and in... 

Fig. 7-10. Calculated values of seasonally varying temperatures at three latitudes in the Northern Hemisphere, plotted as solid lines. Observed zonally averaged temperatures at these latitudes are plotted as symbols.

Fig. 7-14. The seasonal variation of temperature in the Northern Hemisphere plotted as solid lines for DAV10, with permanent ice at high latitudes, and as dashed lines for the reference results, DAV09. The new calculations are started with the same initial values. It takes a few years for the influence of the initial values to die out.

The calculated temperatures are plotted in Figures 7-26 and 7-27, with the changes at the middle and low latitudes in the Southern Hemisphere being quite small. The seasonal amplitude in the south polar region has increased from the Miocene to the present, however, because of the increase in land fraction. Changes in the Northern Hemisphere are the opposite, with the seasonal amplitude having increased slightly at middle and low latitudes because land fraction has increased from the Miocene to the... 

In the northern hemisphere, meteorologists measured record-setting spring and summer temperatures in 2004 and the level of atmospheric carbon dioxide also reached a record high, averaging 379 parts per million, a jump from 2003 levels that was much greater than the average annual increase of 1.8 parts per million recorded over the past decade. 

At sea level, Pj is approximately 1 atm, but exhibits some temporal and spatial variability. For example, the annual mean pressure in the northern hemisphere is 0.969 atm and in the southern hemisphere is 0.974 atm, with monthly averages varying by as much as 0.0001 atm, i.e., about 1 mbar (1 atm = 1013.25 mbar). These fluctuations are caused by spatial and temporal variations in atmospheric temperature and water vapor content associated with weather, and seasonal and longer-term climate shifts. Pj is also affected by diurnal atmospheric tides, and it decreases with increasing altitude above sea level. Some gases, such CO2 and O2, exhibit seasonal variability that is caused in part by seasonal variability in plant and animal activity (see Figures 25.4 and 6.7). 

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