Norwegian research shows that current warming is not unusual

Researchers from the University of Bergen and the University of Colorado studied marine sediment cores from the Norwegian continental margin.  They were able to get accurate dates from lead isotope dating of interspersed volcanic rocks in the core.  They examined oxygen-18 isotopes from the calcium carbonate in the shells of planktonic foraminifera to reconstruct temperature. (Oxygen-18 is a proxy for temperature, see NASA’s Earth Observatory explanation of the method here.)

This allowed the researchers to come up with what they call “near surface water summer temperature.” for the past 2,000 years.  The following graph depicts their temperature reconstruction:


The graph shows that the current warm period is cooler than the Medieval and Roman warm periods.  The researchers report a statistically significant correlation with the Gleissberg solar cycle.  This is more evidence that the forces of natural variability overcome the effect, if any, of anthropogenic carbon dioxide emissions, and it shows that current warming is neither unprecedented nor unusual.


Sejrup, H.P., Haflidason, H. and Andrews, J.T. 2011. A Holocene North Atlantic SST record and regional climate variability. Quaternary Science Reviews 30: 3181-3195.   Abstract here.



  1. What does this study tell us about past sea, land surface and atmospheric GLOBAL temperatures? Nothing. To understand global climate, it’s necessary to collate global data. That has been done. In the United States, the U.S. Global Change Research Program coordinates and integrates federal research on climate. Its 2009 report concluded: “Observations show that warming of the climate is unequivocal. The global warming observed over the past 50 years is due primarily to human-induced emissions of heat-trapping gases. These emissions come mainly from the burning of fossil fuels (coal, oil, and gas), with important contributions from the clearing of forests, agricultural practices, and other activities.” Unlike the regional sample shown above, the USGCRP has collated the global data.

    1. Your argument is spurious. A collation is a collection from individual sources. This is one of those places. Similar data have been reported from other places. Besides, I’m not saying that there has been no warming. You are, again, deflecting the argument. I’m only showing current warming in relation to other warm periods. Does USGCRP have specific evidence to show that recent warming is “due primarily to human-induced emissions of heat-trapping gases?”

  2. First of all, the word collate means to compare and analyze data, which in this case USGCR did. Secondly, you are not “… only showing current warming in relation to other warm periods.” You are showing sea surface temperatures in ONE REGION over a period of time. Lastly, you can see the evidence on which USGCR based it’s conclusions here: JP

  3. Global warming is GLOBAL.  Specific areas may not have lineal rises with others, but there should be some increase in almost all areas.  Furthermore, if global warming is such an active event, how would a marine environment NOT be affected?
    Picking and choosing areas that have had an increased temperature rise in five years doesn’t validate the entire argument that the sky is falling.  An argument that seems to lose traction every time a non-biased research project is done. 
    Just my 2c

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