What happened the last time the icecaps melted?

Illustration for article titled What happened the last time the icecaps melted?

The fact that sea levels are rising probably won't come as a huge surprise. But we now have some much-needed historical context for the melting icecaps and rising waters...and there's zero doubt that, in geological history, higher sea levels meant higher temperatures.


An international team led by researchers at the University of Pennsylvania created the first ever reconstruction of the last 2,000 years worth of changing sea levels. They were able to do this thanks to tiny fossils known as foraminifera, which can be found in sediment cores in North Carolina's coastal marshes.

To make sure these fossils could be used as an accurate barometer of sea level at different points in history, they compared the last 80 years worth of foraminifera data with contemporaneous North Carolina tidal gauge records. Once they had created the reconstructive technique, they then compared that with 300 years of global sea level records.

Here's what they found. The sea level changed very little between 200 and 1,000 C.E., then it began to climb by about half a millimeter per year for 400 years. This fits well with a known climate spike that began in the 11th century, which is known as the Medieval Climate Anomaly. Sea levels drop again in the mid-17th century, which is right on time for the advent of the Little Ice Age, which lasted from 1645 to 1715.

That drop continues until the beginning of the late 19th century, when the industrial revolution was in full swing. At that point, sea levels start climbing at an average rate of two millimeters per year, and the seas have been rising that much ever since. The research confirms what has often been assumed, that there's a very strong link between sea levels and temperatures. More worryingly, it also seems to confirm just how uniquely pronounced the current climate change really is.

Via Proceedings for the National Academy of Science. Image via.


I hate to nitpick here, but the headline implies that the article contains some sort of information about the effect of melting icecaps in the geologic past, but the article merely covers how data were obtained to indicate that sea level is linked to global temperature.

Unfortunately, by using the scientifically controversial term "Medieval Climate Anomaly" in regard to the well-known spike in global temperature that occurred in the 11th century, the article also abandons objectivity in favor of global warming alarmist rhetoric. This alarmist stance concludes with the scientifically insupportable comment, "it also SEEMS to confirm." Science does not SEEM to confirm anything; it either empirically supports a supposition, or it does not. In this case, by referring to a vast body of collected data as an "anomaly," the article follows global warming rhetoric by discarding inconvenient contradictory data in a manner that is unsupportable by scientific method.

Two thousand years is barely a blink of the geologic eye. Data collected for this period are certainly worth studying, but when compared to true geologic time, using this data to draw climatalogical conclusions is like polling a dozen people in a limited area and using their opinions to assess the will of the entire human race. No, the data in question draws no conclusion. However, it does add to what we know. In using that knowledge, we cannot ignore the part of that data that fails to support what we already believe. That is institutionalized confirmation-bias on the same magnitude as the 16th century church repressing the discoveries of Galileo.

From this, you may jump to the conclusion that I do not support global warming theory. That conclusion is inaccurate. I do see that there is a trend that humanity must examine and understand to accurately determine our impact on the environment. What I cannot abide is anecdotal observation masquerading as science, selectively quoting climate-change scripture to falsely support a point of view that has yet to be proven scientifically.