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Developments in the Middle Ages

Figure shows the evolution of temperatures during the last 2000 years. Temperatures in the graph are averages figured one every 10 years. Since there is no direct temperature measurements in this period, temperatures were reconstructed based on thickness measurements of tree ring growth and ice thickness. Dating of tree rings can be made on the basis of determining the concentration of carbon-14 biological activity in the last thousand years is shown at right.

Climatic variations in the Middle Ages were not so great as during glaciation. However, the last thousand years there is a warm period in the tenth century and the eleventh-century medieval period called maximum. It is time when the Vikings discovered Greenland, whose name, “Green Country” shows a landscape with vegetation, not snow and ice covered.

But still, during (1550 – 1850) was followed by a cooling small ice age, the winters were very cold, especially that between the years 1708 – 1709

Developments in the current period

As temperatures reconstructed from climatologists, the last decade of the twentieth century and early twenty-first century is the warmest period of the last 2000 years (see figure above). The current era is hot a few tenths of a degree from medieval peak.

Causes of warming

The climate is changing due to external forcing, depending on the influence of movement in orbit around the sun, volcanic eruptions and greenhouse effect. Share of various causes of warming is under investigation, but the consensus of scientists is that the main cause is increasing greenhouse gas concentrations due to human activities in the era of industrialization. Especially in the last 50 years, when detailed data are available, this is obvious. However, there are other assumptions, which gives heating solar activity variations

The effects of forcing are instantaneous. Studies indicate that climate models, even if concentrations of greenhouse could find would remain at that of 2000, climate would still have warm by 0.5 ° C.

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