A paper published Friday in the Journal of Geophysical Research (GRL) finds that a known and natural atmospheric oscillation, the Southern Annular Mode or SAM, is correlated with observed increases in cloud cover resulting in regional cooling of approximately -2.5C. See for example this comparison from the paper with MODIS satellite data:
From UCAR:
The Southern Annular Mode (SAM), which is defined by changes in the westerly winds that are driven by temperature contrasts between the tropics and southern polar areas. The annular modes generally take a circular pattern (‘annular’ means ring-shaped) and see-saw between positive and negative phases for weeks or months. In the SAM’s positive mode, the ring is stronger and further south, inhibiting Antarctic air outbreaks. In the negative mode, a weaker, more variable vortex allows Antarctic air to spill north more easily.
The Southern Annular Mode has steadily trended positive in recent decades. Computer models indicate this trend is related to ozone depletion above Antarctica and increases in greenhouse gases. (Image courtesy Jianping Li, China Institute for Atmospheric Physics.)
As presently programmed, climate models assume clouds result in net positive feedback and increased temperatures, however this new paper and several others that have recently been published show that clouds instead result in net negative feedback and cooling.
Key Points of the paper:
- Sudden regional increases in cloud cover are detected over S. America
- Changes linked to the Southern Annular Mode
- The cloud changes are associated with regional temperature reductions
The paper and abstract:
Understanding sudden changes in cloud amount: The Southern Annular Mode and South American weather fluctuations
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 117, D13103, 7 PP., 2012
doi:10.1029/2012JD017626
Benjamin A. Laken Instituto de Astrofísica de Canarias, La Laguna, Spain, Department of Astrophysics, Faculty of Physics, Universidad de La Laguna, La Laguna, Spain
Enric Pallé Instituto de Astrofísica de Canarias, La Laguna, Spain, Department of Astrophysics, Faculty of Physics, Universidad de La Laguna, La Laguna, Spain
This work investigates the cause and effects of extreme changes in synoptic-scale cloud cover operating at daily timescales using a variety of satellite-based and reanalysis data sets. It is found that the largest sudden increases detected in globally averaged cloud cover over the last ten years of satellite-based observations occur following positively correlated shifts in the phase of the Southern Annular Mode (SAM) index. The associated pressure anomalies are found to generate frontal cloud formation over large areas of the South American continent, increasing regional cloud cover by up to 20%; these changes are correlated to statistically significant reductions in local temperatures of approximately −2.5°C with a +1 day time lag, indicating the SAM index is associated with large scale weather fluctuations over South America.
joel shore,
Give it up, loser. If it weren’t for moving the goal posts you wouldn’t have much to say.
I don’t “let” anyone do anything, they post what they find relevant. And you “explain” nothing, you only accuse people you don’t agree with as being “ideologues”. That’s because you cannot refute what I post.
I can defend anything I post, you just don’t like it when I easily deconstruct your globalobney nonsense. All you ever post is baseless opinion that tries to contradict what Planet Earth is telling us: CAGW is complete nonsense.
Run along now to your thinly trafficked RealClimatePropaganda or Pseudo-Skeptical Pseudo-Science blogs. You desperately need some new talking points. The ones you’ve been using are old and busted.
Shawnhet says:
Since you are getting more WV in an atmosphere that can also hold more WV before that WV condenses, it is not obvious how this goes. I am not saying it leads to less cloudiness. I am just saying that things are not so obvious that it leads to more that you can conclude this from simple arguments.
You are basically arguing that you can tell from simple principles what will happen in processes that climate scientists have been discussing for years. You are basically saying that you are so much smarter than them that you can intuitively figure it out while they are struggling to understand how cloudiness changes! I think such a monumental claim puts the responsibility in your court to come up with compelling arguments backed up by data to supportr this.
Joel Shore:”Since you are getting more WV in an atmosphere that can also hold more WV before that WV condenses, it is not obvious how this goes. I am not saying it leads to less cloudiness. I am just saying that things are not so obvious that it leads to more that you can conclude this from simple arguments.
You are basically arguing that you can tell from simple principles what will happen in processes that climate scientists have been discussing for years. You are basically saying that you are so much smarter than them that you can intuitively figure it out while they are struggling to understand how cloudiness changes! I think such a monumental claim puts the responsibility in your court to come up with compelling arguments backed up by data to supportr this.”
I fully understand that my simple model *might be* wrong but just because something is simple is not an argument that it *is* wrong What you fail to recognize is that all the reasons you have raised why it might be wrong *do not hold water*. For instance, you are correct that warmer air will hold more WV but we can go out and observe what the effects of different levels of water vapor and temperatures in the atmosphere are on the overall levels of cloudiness but, by and large, this data will agree with my position. Do you really dispute that, a climate with an average RH of 60% and an average temp of 20C will not be cloudier that one with an RH of 60% and a temperature of 10C? I would say that this is a pretty compelling relationship.
IAC, just to be fair, I believe that it is plausible that cloud feedback might be negative but it would most likely require that RH not be constant. This would involve clouds not lasting as long when there is more WV in the air. The logic would go like this, more WV forms more cloud but because precipitation efficiency is greater they rain themselves out faster and last less long. This would be, as far as I can tell, consistent with the evidence and would involve more that just saying something really complicated and mysterious *might be* going on ;).
Cheers, 🙂