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Did the Climate ‘Shift’ in 2001/02?
Kyle Swanson and Anastasios Tsonis have a new GRL paper ‘in press’ entitled: ‘Has the climate recently shifted?’
The Abstract states:
This paper provides an update to an earlier work that showed specific changes in the aggregate time evolution of major Northern Hemispheric atmospheric and oceanic modes of variability serve as a harbinger of climate shifts. Specifically, when the major modes of Northern Hemisphere climate variability are synchronized, or resonate, and the coupling between those modes simultaneously increases, the climate system appears to be thrown into a new state, marked by a break in the global mean temperature trend and in the character of El Ni˜no/Southern Oscillation variability. Here, a new and improved means to quantify the coupling between climate modes confirms that another synchronization of these modes, followed by an increase in coupling occurred in 2001/02. This suggests that a break in the global mean temperature trend from the consistent warming over the 1976/77–2001/02 period may have occurred.
The paper concludes:
If as suggested here, a dynamically driven climate shift has occurred, the duration of similar shifts during the 20th century suggests the new global mean temperature trend may persist for several decades. Of course, it is purely speculative to presume that the global mean temperature will remain near current levels for such an extended period of time. Moreover, we caution that the shifts described here are presumably superimposed upon a long term warming trend due to anthropogenic forcing. However, the nature of these past shifts in climate state suggests the possibility of near constant temperature lasting a decade or more into the future must at least be entertained. The apparent lack of a proximate cause behind the halt in warming post 2001/02 challenges our understanding of the climate system, specifically the physical reasoning and causal links between longer time-scale modes of internal climate variability and the impact of such modes upon global temperature. Fortunately, climate science is rapidly developing the tools to meet this challenge, as in the near future it will be possible to attribute cause and effect in decadal scale climate variability within the context of a seamless climate forecast system [Palmer et al. 2008]. Doing so is vital, as the future evolution of the global mean temperature may hold surprises on both the warm and cold ends of the spectrum due entirely to internal variability that lie well outside the envelope of a steadily increasing global mean temperature.
March 6th, 2009 at 12:23 am
“the shifts described here are presumably superimposed upon a long term warming trend”
What does “presumably” mean in this sentence?
“We can’t find the warming trend because the ‘natural’ variations of unknown origin are overwhelming, but since there’s a consensus and all, there must be a warming trend in there somewhere.”
March 6th, 2009 at 12:56 am
Yes, it is customary to give the consenus a nod even if the paper doesn’t support it.
March 17th, 2009 at 1:25 am
Hmmmm, and just where is the evidence in the most recent data for “a steadily increasing global mean temperature”??