There are now more studies that show recent warming is unprecedented – in magnitude and speed and cause — than you can shake a stick at!
As with a pride of lions, and a conspiracy of disinformers [or is that a delusion of disinformers?], perhaps the grouping should get its own name, like “a team of hockey sticks” (see “The Curious Case of the Hockey Stick that Didn’t Disappear“).
- GRL: “We conclude that the 20th century warming of the incoming intermediate North Atlantic water has had no equivalent during the last thousand years.“
- JGR: “The last decades of the past millennium are characterized again by warm temperatures that seem to be unprecedented in the context of the last 1600 years.” [figure below]
Reconstructed tropical South American temperature anomalies (normalized to the 1961–1990AD average) for the last ∼1600 years (red curve, smoothed with a 39‐year Gaussian filter). The shaded region envelops the ±2s uncertainty as derived from the validation period. Poor core quality precluded any chemical analysis for the time interval between 1580 and 1640 AD.
Yes, the 39‐year Gaussian filter appears to wipe out over half of the warming since 1950 as this NASA chart makes clear:
As WAG notes, within a few decades, nobody is going to be talking about hockey sticks, they will be talking about right angles (or hockey skates):
The rate of human-driven warming in the last century has exceeded the rate of the underlying natural trend by more than a factor of 10, possibly much more. And warming this century on our current path of unrestricted greenhouse gas emissions is projected to cause a rate of warming that is another factor of 5 or more greater than that of the last century. We are punching the climate beast — and she ain’t happy about it!
What’s amusing is that Anthony Watts actually focuses on this Journal of Geophysical Research paper, “Ammonium concentration in ice cores: A new proxy for regional temperature reconstruction?” in his post, “Study: Ammonium as ice core proxy shows strong Medieval Warm Period in the tropics.”
For the record, even a moderate MWP (even if it were global, which remains unproven) does nothing whatsoever to undermine our understanding of human-caused global warming. The temperature trend in the past millennium prior to about 1850 is well explained in the scientific literature as primarily due to changes in the solar forcing along with the effect of volcanoes, whereas the recent rise in temperature has been driven primarily — if not almost entirely — by human activity (see Scientist: “Our conclusions were misinterpreted” by Inhofe, CO2 — but not the sun — “is significantly correlated” with temperature since 1850 and a post to be named later).
The Geophysical Research Letters paper, “Twentieth century warming in deep waters of the Gulf of St. Lawrence: A unique feature of the last millennium” concludes:
… irrespective of the precise mechanisms responsible for the temperature variations reconstructed from core MD99‐2220, it is unquestionable that the last century has been marked there by a warming trend having no equivalent over the last millennium.
For those keeping score at home, here are a few more members of the team of hockey sticks (although the last two aren’t actually independent, as discussed here).
And from McShane and Wyner (2010):
And yes, McShane and Wyner has been debunked in the blogosphere — see I went to a statistician fight and a hockey stick broke out — and is currently being eviscerated in the original journal itself.