An honest and balanced understanding of the position of slavery in the American experience requires a serious attempt to place the institution in historical context and to clear-away some of the common myths and distortions.
Posted on February 6, by curryja Comments by Greg Goodman Satellite data for the period surrounding the Mt Pinatubo eruption in provide a means of estimating the scale of the volcanic forcing in the tropics. A simple relaxation model is used to examine how temporal evolution of the climate response will differ from the that of the radiative forcing.
Taking this difference into account is essential for proper detection and attribution of the relevant physical processes.
Estimations are derived for both the forcing and time-constant of the climate response. These are found to support values derived in earlier studies which vary considerably from those of current climate models.
The implications of these differences in inferring climate sensitivity are discussed. The study reveals the importance of secondary effects of major eruptions pointing to a persistent warming effect in the decade following the eruption.
The inadequacy of the traditional application of linear regression to climate data is highlighted, showing how this will typically lead to erroneous results and thus the likelihood of false attribution. The implications of this false attribution to the post divergence between climate models and observations is discussed.
Analysis of these radiation measurements allows an assessment of the system response to changes in the radiation budget.
Pinatubo eruption provides a particularly useful natural experiment, since the spread of the effects were centred in the tropics and dispersed fairly evenly between the hemispheres. The derived scaling factor to convert AOD into radiative flux, supports earlier estimations  based on observations from the El Chichon eruption.
These observationally derived values of the strength of the radiative disturbance caused by major stratospheric eruptions are considerably greater than those currently used as input parameters for general circulation climate models GCMs.
Method Changes in net TOA radiative flux, measured by satellite, were compared to volcanic forcing estimated from measurements of atmospheric optical depth. Regional optical depth data, with monthly resolution, are available in latitude bands for four height ranges between 15 and 35 km [DS1] and these values were averaged from 20S to 20N to provide a monthly mean time series for the tropics.
Since optical depth is a logarithmic scale, the values for the four height bands were added at each geographic location. Lacis et al  suggest that aerosol radiative forcing can be approximated by a linear scaling factor of AOD over the range of values concerned.
This is the approach usually adopted in IPCC reviewed assessments and is used here. As a result the vertical summations are averaged across the tropical latitude range for comparison with radiation data.
One notable effect of the eruption of Mt Pinatubo on tropical energy balance is a variation in the nature of the annual cycle, as see by subtracting the pre-eruption, mean annual variation. Following the eruption, the residual variability also shows a six monthly cycle.
The semi-annual variability changed and only returned to similar levels after the El Nino. Figure 1 showing the variability of the annual cycle in net TOA radiation flux in tropics. Click to enlarge It follows that using a single period as the basis for the anomaly leaves significant annual residuals.
To minimise the residual, three different periods each a multiple of 12 months were used to remove the annual variations: The three resultant anomaly series were combined, ensuring the difference in the means of each period were respected. The mean of the earlier, pre-eruption annual cycles was taken as the zero reference for the whole series.
There is a clearly repetitive variation during the pre-eruption period that produces a significant downward trend starting 18 months before the Mt. Since it may be important not to confound this with the variation due to the volcanic aerosols, it was characterised by fitting a simple cosine function.
This was subtracted from the fitting period.
Though the degree to which this can be reasonably assumed to continue is speculative, it seems some account needs to be taken of this pre-existing variability.
The effect this has on the result of the analysis is assessed. The break of four months in the ERBE data at the end of was filled with the anomaly mean for the period to provide a continuous series. This involves some approximations. Firstly, since the data is restricted to the tropical regions, the vertical energy budget does not fully account for energy entering and leaving the region.Abstract: The bacterial flagellum is a complex molecular system with multiple components required for functional motility.
Such systems are sometimes proposed as puzzles for evolutionary theory on the assumption that selection would have no function to act on until all components are in place. Many important points are made in this Commentary by David.
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Hi 1. Iceland is an island created by magma (high basalt content) pouring out between separating plates. Subduction areas volcanoes are result of sinking and melting of the crust, thus amount of magma expelled is dependent the amount of sinking material.
Michał Kalecki ([ˈmixau̯ kaˈlɛt͡ski]; 22 June – 18 April ) was a Polish plombier-nemours.com the course of his life, Kalecki worked at the London School of Economics, University of Cambridge, University of Oxford and Warsaw School of Economics and was an economic advisor to the governments of Poland, France, Cuba, Israel, Mexico and India.
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One of the key problems of present-day economics is the role of money and other liquid assets in the structure of economic decisions—particularly in the decisions of firms and households to save and to invest in durable real assets, such as factories, machinery, houses, and vehicles.