Drill cores taken from Greenland's vast ice sheets show that Earth's climate is capable of very rapid transitions - more of a mystery is why abrupt climate changes like that happen.
Layers of ancient snow accumulated and became compact to form the ice-sheets we see today. Each layer of ice can reveal past temperatures and even evidence for the timing and magnitude of distant storms or volcanic eruptions. By drilling cores in the ice scientists have reconstructed an incredible record of past climates. Those temperature records from Greenland covered only the last 100,000 years or so.
The new reconstruction is based on the much longer ice core temperature record retrieved from Antarctica and uses a mathematical formulation to extend the Greenland record beyond its current limit. Some calibration is in order, they note. Any time you have an assumption-based model there may be issues of method but, as Dr. Stephen Barker of Cardiff University explains, "Our approach is based on an earlier suggestion that the record of Antarctic temperature variability could be derived from the Greenland record. "However, we turned this idea on its head to derive a much longer record for Greenland using the available records from Antarctica."
Their prediction says that abrupt climate change has been a systemic feature of Earth's climate for hundreds of thousands of years and may play an active role in longer term climate variability through its influence on ice age terminations.
Barker added: "It is intriguing to get an insight into what abrupt climate variability may have looked like before the Greenland records begin. We now have to wait until longer Greenland records are produced so that we can see how successful our prediction is."
The new predictions provide an extended testing bed for the climate models that are used to predict future climate variability.
The collaborative research was funded in part by a Leverhulme Trust Philip Leverhulme Prize awarded to Barker at Cardiff University. The Natural Environment Research Council and National Science Foundation in the United States also funded the research.