John Penhallurick’s Blog 2 Evidence from past climate change


Evidence from past climate change

The IPCC and its supporters seem to assume that the climate showed no change prior to the advent of the industrial age in Europe. The authors and supporters of the notorious “Hockey Stick” version of climate change over the last 1,000 years certainly tried to give that impression. An obvious reason for this position is to try to show that the most recent warming is unique, and so must be due to changing human activities. This is a total fallacy. It is no accident that many of the scientists who do not subscribe to the IPCC’s propaganda come from a background as geologists or paleoclimatologists. It cannot be denied that there have been a number of significant climate changes over the last three thousand years, as can be seen in Figure 1. The highest temperatures in the last 11,000 years were during the Holocene  Climate Optima which occurred from about 8,000-6,000

Figure 1

Global Temperature Variation over the last 11,000 years

years BP and again from 5,000 to 3,500 BP. Then we have the Minoan Warming from about 3,200-2,900 years BP; then a very cold period from about 2,800-2,400 year BP. This was followed by the Roman Warming from about 2,300-1,700 year BP; the minor Dark Ages Cooling; then the Medieval Warm Period, followed by the Little Ice Age, and since about 190-180 years BP the Modern Warming. Such data are nonetheless embarrassing for the warmists’ case, as human emissions can have played no part in climate change prior to 1850. Taking account of this historical perspective, it is inconceivable that the recent warming is solely or even mainly due to a new factor, human emissions of CO2, and that natural variability, which was responsible for all previous warmings and coolings, has suddenly stopped playing any role.

One response that I have received from supporters of the IPCC is to ask why we should worry about the past when the needs of the present and future are so important, which needs no further comment. Judged in terms of the requirements of objective, evidence-based science, such a response is beneatrh contempt. Another standard response to such data from such people is to claim that the climate fluctuations mentioned above affected only Europe. But these periods were worldwide in their effects. Just to cite evidence from the two most recent completed climate fluctuations: there is ample evidence that the Early Medieval Warming 900-1300 AD was global. Tree ring studies from California suggest North America was also warmer (see Becker, W. S. 2001). Greenland was settled by the Vikings during this period. In East Africa, the same period of warming is shown from evidence using sediments, fossil diatoms and numbers of species of midges, which shows alternating dry and wet conditions. China flourished during this period. In Argentina, the carbon chemistry of prehistoric villages shows that villagers clustered in the lower valleys during the Dark Age Cooling; that they moved upslope to 4300m in the Central Peruvian Andes during the period of the Early Medieval Warming, and that they moved back downslope with the onset of the Little Ice Age in 1320. (see Cioccale, M. A, 1999).

Recent scientific data suggest that far from the Early Medieval Warming being a minor and local fluctuation, temperatures up to 1° warmer than the current temperature occurred. Surge & Barrett (2012) stated: Seasonal sea-surface temperature (SST) variability during the Medieval Climate Anomaly (MCA), which corresponds to the height of Viking exploration (800–1200 AD), was estimated using oxygen isotope ratios (δ18O) obtained from high-resolution samples micromilled from archaeological shells of the European limpet,Patella vulgata. Our findings illustrate the advantage of targeting SST archives from fast-growing, short-lived molluscs that capture summer and winter seasons simultaneously. Shells from the 10th to 12th centuries (early MCA) were collected from well-stratified horizons, which accumulated in Viking shell and fish middens at Quoygrew on Westray in the archipelago of Orkney, Scotland. Their ages were constrained based on artifacts and radiocarbon dating of bone, charred cereal grain, and the shells used in this study. We used measured δ18OWATER values taken from nearby Rack Wick Bay (average 0.31 ± 0.17‰ VSMOW, n = 11) to estimate SST from δ18OSHELL values. The standard deviation of δ18OWATER values resulted in an error in SST estimates of ± 0.7 °C. The coldest winter months recorded in the shells averaged 6.0 ± 0.6 °C and the warmest summer months averaged 14.1 ± 0.7 °C. Winter and summer SST during the late 20th century (1961–1990) was 7.77 ± 0.40 °C and 12.42 ± 0.41 °C, respectively. Thus, during the 10th to 12th centuries winters were colder and summers were warmer by ~2°C and seasonality was higher relative to the late 20th century. Without the benefit of seasonal resolution, SST averaged from shell time series would be weighted toward the fast-growing summer season, resulting in the conclusion that the early MCA was warmer than the late 20th century by ~ 1 °C. This conclusion is broadly true for the summer season, but not true for the winter season. Higher seasonality and cooler winters during early medieval times may result from a weakened North Atlantic Oscillation index.

The beginning of the Little Ice Age 1280-1300 to 1850 AD (which none of the Climate models can explain) coincided with the Wolf Minimum of the Sun(1280-1340 AD). Other solar minima during this period include the Spörer Minimum (1450-1540 AD), the Maunder Minimum (1645-1715 AD), the coldest period in the Little Ice Age; and the Dalton Minimum (1795-1825 AD). Not surprisingly, since these events involved solar minima, their effects were experienced world-wide. That it affected all continents and all major islands from New Zealand in the South Pacific to Svalbard in the ArcticSea is clear. (see Grove, J. M. 1988) The Little Ice Age was not a uniformly cold episode, however. In Europe and North America, at least six phases of glacial expansion occurred. These were separated by warmer periods.

You can now either go back to my post no.1 to access all pages by clicking on the following line

1. Evidence that the IPCC’s case is a fraud.

or you can go on to the next document:

3. How the IPCC has corrupted science.

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About jpenhall

I am a keen birder and have devoted my life especially since retirement to a study of the world's birds. But I was also a professor, with thirty years experience of both carrying out and evaluating research.But I detest shoddy research. Thus I reject almost wholly the propaganda of the IPCC and its minions
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One Response to John Penhallurick’s Blog 2 Evidence from past climate change

  1. Pingback: John Penhallurick’s Blog 1:Evidence that the IPCC’s case is a fraud | jpenhall

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