Contrary to the global warmers' computer predictions, the concentrations of carbon dioxide in the atmosphere, the most important among the man-made greenhouse gases, were out of phase with the changes of near-surface air temperature, both recently and in the distant past. This is clearly seen in Antarctic and Greenland ice cores, where high CO2 concentrations in air bubbles preserved in polar ice appear 1,000 to 13,000 years after a change in the isotopic composition of H2O, signalling the warming of the atmosphere. (29) In ancient times, the CO2 concentration in the air has been significantly higher than today, with no dramatic impact on the temperature. In the Eocene period (50 million years ago), this concentration was 6 times larger than now, but the temperature was only 1.5°C higher. In the Cretaceous period (90 million years ago), the CO2 concentration was 7 times higher than today, and in the Carboniferous period (340 million years ago), the CO2 concentration was nearly 12 times higher. (30) When the CO2 concentration was 18 times higher, 440 million years ago (during the Ordovician period), glaciers existed on the continents of both hemispheres.
At the end of the 19th Century, the amount of CO2 discharged into the atmosphere by world industry was 13 times smaller than now. (31) But the climate at that time had warmed up, as a result of natural causes, emerging from the 500-year long Little Ice Age, which prevailed approximately from 1350 to 1880. This was not a regional European phenomenon, but extended throughout the whole Earth( 19,20) During this epoch, the average global temperature was 1°C lower than now. Festivals were organized on the frozen Thames River, and people travelled from Poland to Sweden, crossing the Baltic Sea on sleighs and staying overnight in a tavern build on ice.
This epoch is well illustrated by the paintings by Pieter Breughel and Hendrick Avercamp. In the mountains of Scotland, the snowline stretched down 300 to 400 meters lower than today. In the vicinity of Iceland and Greenland, the sea ice was so extensive that the access to a Greenland Viking colony, established in 985, was completely cut off; the colony was finally smashed by the Little Ice Age.
All this was preceded by the Middle Ages Warming, which lasted for more than 300 years (900 to 1100), and during which the temperature reached its maximum (1.5°C more than today) around the year 990. Both the Little Ice Age and the Middle Ages Warming, were not regional phenomena as implied by Mann and his co-authors, (32) but were global and were observed around the North Atlantic Ocean, in Europe, Asia, South America, Australia, and Antarctica. (33,34)
During the Medieval Warming, the forest boundary in Canada reached 130 kilometers farther north than today, and in Poland, England, and Scotland vineyards for altar wine production flourished—only to be destroyed by the Little Ice Age. Still earlier, 3,500 to 6,000 years ago, a long-lasting Holocene Warming took place, when the average air temperature exceeded the current one by 2°C (See Direct Temperatures Measured In A Greenland Glacier Bore Hole ).
The Little Ice Age is not yet completely behind us. Stenothermal (warm-loving) diatom species, which reigned in the Baltic Sea during the Medieval Warming, have not yet returned. (35) Diatom assemblages obtained from sediment core from the seabed of the north Icelandic shelf indicate that during the past 4,600 years the warmest summer sea-surface temperatures, about 8.1°C, occurred at 4,400 years before the present. Thereafter the climate cooled, with a warmer interlude of about 1°C near 850 years before the present. This was followed again by a cold span of the Little Ice Age, which brought mean summer sea-surface temperatures down by about 2.2°C. Today's temperature of only 6.3°C still has not reached the Holocene warming level of 8.1°C. (36)
The fastest temperature growth occurred in the early 20th Century, and the maximum was reached around 1940. It was then that the mountain and Arctic glaciers were shrinking violently, but their retreat from the record sizes (during the coldest part of Little Ice Age) had started 200 years earlier, around 1750, when no one even dreamed of industrial CO2 emissions. An illustration of this process is a map of glacier front changes between 1750 and 1961, at what is probably the best studied Storbreen Glacier in Norway, in which the first measurements of CO2 in ice were performed in 1956 (See Retreat Of The Storbreen Glacier In Norway). The attack of glaciers on Swiss villages in the 17th and 18th centuries — sometimes the velocity of ice movement reached 20 meters annually, destroying homes and fields — as perceived as a calamity. Yet, the withdrawal of glaciers in the 20th Century has been deemed, somewhat foolishly, to be a disaster.
Since the exceptionally hot 1940s, until 1975, the Earth's climate cooled down by about 0.3°C, despite a more than three-fold increase of annual industrial CO2 emission during this period. After 1975, meteorological station measurements indicated that the average global temperature started to rise again, despite the decline in "human" CO2 emissions. However, it turns out that it was probably a measuring artifact, brought about by the growth of the cities and resulting "urban heat island" effect. Meteorological stations, which used to be sited outside of urban centers, have been absorbed by the cities, where the temperature is higher than in the countryside.
Outside the cities of the United States and Europe, the observed temperature is lower, rather than higher, as demonstrated by the data of NASA's Goddard Institute, reviewed recently by J. Daly. (37)
The same is true also for the polar regions, where the models predict the largest increase in air temperature. As stated by Rajmund Przybylak, a climatologist from the Nicolaus Copernicus University in Torun, Poland, in polar regions "warming and cooling epochs should be seen most clearly. . . and should also occur earlier than in other parts of the world." Therefore, these regions, he says, "should play a very important role in the detection of global changes." (38)
Przybylak collected data covering the period 1874 to 2000, from 46 Arctic and subarctic stations managed by Danish, Norwegian, American, Canadian, and Russian meteorological and other institutes. His study demonstrates the following:
These findings are similar to temperature changes in the Arctic found in data collected by NASA(37,38) and in earlier studies reviewed by Jaworowski. (13)
In a new study covering the air surface temperature and sea level pressure data from 70 stations in the circum-Arctic region northward of 62°N, over the period from 1875 to 2000, Polyakov et al. (39) found that the temperature data consist of two cold and two warm phases of multidecadal variability, at a time scale of 50 to 80 years, superimposed on a background of a long warming trend. This variability appears to originate in the North Atlantic, and is likely induced by slow changes in oceanic thermohaline circulation, and in the complex interactions between the Arctic and North Atlantic.
The two warm periods occurred in the Arctic in the late 1930s through the early 1940s, and in the 1980s through the 1990s. The earlier period was warmer than the last two decades. Since 1875, the Arctic has warmed by 1.2°C, and for the entire recorded temperature record, the temperature warming trend was 0.094°C per decade. For the 20th Century alone, the warming trend was 0.05°C per decade; that is, close to the Northern Hemispheric trend of 0.06°C per decade. Because the temperature in the 1930s-1940s was higher than in recent decades, a trend calculated for the period 1920 to the present actually shows cooling.