It is well formulated by the the IPCC climate doomsday hive-mind that only CO2 can produce unprecedented global warming, plus any other extreme climate change - thus, the low Medieval CO2 levels must be the actual cause of Scottish temperatures being 1 degree higher than modern temperatures
Read here. The global warming alarmists have established a multi-billion dollar industry based purely on the hypothesis that high atmospheric CO2 levels cause unprecedented warming. This means that no other natural, solar and/or cosmic factors could be responsible.
Yet, in study after study, researchers keep discovering long ago periods (when CO2 levels were low) that experienced extremely high temperatures - indeed, unprecedented warming. The latest such study to do so, was the research conducted on limpet shells from the waters off Scotland's coast.
"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...Our findings illustrate the advantage of targeting SST archives from fast-growing, short-lived molluscs that capture summer and winter seasons simultaneously...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." [Donna Surge, James H. Barrett 2012: Palaeogeography, Palaeoclimatology, Palaeoecology]
Because of the restrictive orthodoxy of the IPCC green fundamentalists, the only conclusion that can be drawn from this new study, and others that find unprecedented warming in other regions, is that indeed the magical CO2 greenhouse gas has the power to cause extreme temperatures even under low CO2 conditions. This must be since the IPCC consensus has determined no other forces could possibly produce such high temperatures.
Of course, when one considers the above IPCC science, one quickly realizes how moronic their CO2 hypothesis is. It's so moronic, that even the IPCC realized it, and that's why the hockey-stick temperature representation came about. Since their CO2 hypothesis could not explain the Medieval Warming, they just found themselves a "scientist" who would erase the earlier Medieval high temperatures - and voila, the infamous hockey-stick came about.
Conclusion: This new study and previous research provides an abundance of scientific evidence that the Medieval Warming existed across many regions of the Northern and Southern Hemisphere. It was an unprecedented global warming. This warming was not due to high CO2 levels, which ultimately means that other natural/solar/cosmic forces are the primary cause of both extreme climate and temperature changes of the past, in the present and for the future.