An underwater hockey stick
Posted on 1 October 2010 by John Cook
A new paper adds another piece of the puzzle to our understanding of past climate change. This one is Twentieth century warming in deep waters of the Gulf of St. Lawrence: A unique feature of the last millennium (Thibodeau et al 2010). In this paper, the authors reconstruct North Atlantic water temperature over the last millennium using oxygen isotopes from ocean sediment cores on the Canadian east coast. What they found is the warming over the 20th Century has had no equivalent over the last thousand years.
Figure 1: Temperature anomaly calculated from oxygen isotope composition. The grey lines to the right of the graph are shaded as that part of the core was disturbed by the coring process.
As the temperature record only represents one particular region, they also plot two reconstructions of Northern Hemisphere temperature which I've reproduced below (I use a colour version of the Moberg reconstruction with the instrumental record included).
Figure 2: Two reconstructions of Northern Hemisphere temperature from 1100 to present (Crowley 2000, Moberg et al 2005).
The growing body of evidence is strengthening the view that current warming is unprecedented over the past 1000 years, as confirmed by a number of temperature reconstructions.