Guest Post by Wim Röst
Today ‘warm’ is strongly connected with ‘climate change’, if not with ‘dangerous climate change’. In the minds of people ‘cold’ should be more stable. But, paleo data show that it is ‘cold’ that is unstable. While ‘warm’ always shows a high stability in climatic conditions.
Warm is stable, Cold is ‘change’
As is clearly visible in figure 1, temperatures were much more stable during the Pliocene, 5 to 3 million years ago: to the left in figure 1. The temperatures were a little bit warmer than they are now (the dashed line = present temperature). During the warm Pliocene, temperatures showed little variability when compared to the Quaternary period, the geologic period we now live in.
Figure 1: Temperature development in the last five million years according to the Antarctic Vostok Ice Core. ‘Warm’ shows small variances in temperature. ‘Cold’ means high variability.
The difference in temperature variance is better shown, when we look at the two parts on both ends of the past 5 million years in figure 2.
Figure 2: Variance in temperature during warm and cold periods – the same graphic as above. The length of the arrows shows the difference in variance between ‘warm’ and ‘cold’ phases. Variance during cycles grows during the period from less than two degrees to more than 8 degrees. On the right of the figure we find ‘climate change’ in perfect form, in the coldest part of the Quaternary.
Greenland ice cores show, in more detail, over a shorter period, the same pattern of instability / stability. Until 15,000 years ago in the full depth of the most recent glacial advance, variance even within a 1000-year period was huge. In the last 10,000 years, our warm Holocene temperatures (upper right) only showed small fluctuations – if compared to the glacial period as shown left below. Figure 3.
Figure 3: Variance in temperatures during the last 21.000 years according to NGRIP Greenland ice core
Surface temperatures show the same pattern: as it becomes colder (red line in figure 4), variance grows. Until 5 million years ago, the variance between smaller periods was up to two degrees. At the end of the Quaternary, variance grew to 6 degrees or more. Warm was stable and ‘cold’ meant ‘intense climate change’.
Figure 4: Variance in surface temperatures from the Pliocene into the Pleistocene.
Causes of the growing climate instability at lowering temperatures
The unstable Quaternary is characterised by glacial periods in which large surfaces are covered by ice and snow, large areas that are reflecting the sun and in doing so, strongly are cooling the Earth as a whole. ‘Snow coverage’ has a seasonal character and variations in the snow cover enhance the yearly, decadal and multidecadal temperature changes. Those temperature changes have huge consequences for other aspects of the climate system like winds, evaporation, the strength and the position of pressure areas. As figure 3 shows, the ‘glacial climate state’ is a very unstable climate state.
The switch into the interglacial showed huge temperature rises – in part, due to the effect of diminishing snow and ice – and only during the warmer periods less variance appears as shown in figure 3. Ice and snow lost their destabilizing role as soon as temperatures reached a certain level: the level we know from the warmer period just before the Quaternary.
Unfortunately, interglacials (like the period we are living in) are short lived. The stability of our Holocene could end as soon as new cooling enhances the growth of surfaces with ice and snow.
Contrary to mainstream thinking, warm is not unstable but very stable. Very unstable are colder periods as shown in our Quaternary.
Within the glacials a huge variance is demonstrated, reflecting a very unstable climate state. Large ‘climate changes’ are shown many times even within every 1000-year period of the cold glacial.
The only possible conclusions are, that ‘Warm is stable’ and that ‘Cold means Climate Change’.
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About the author: Wim Röst studied human geography in Utrecht, the Netherlands. The above is his personal view. He is not connected to firms or foundations nor is he funded by government(s).
Andy May was so kind to read the original text and improve the English where necessary. Thanks Andy!