Northern hemisphere warming more rapidly than the south

University of Alabama at Huntsville (UAH)) MSU satellite temperature data for the lower troposphere still has the northern hemisphere warming at a greater rate than the southern. In March 2008 the difference is trending at a huge 0.52 degrees C over the 29 years (352 months) of the data, Dec 1978 to Mar 2008.

7 comments to Northern hemisphere warming more rapidly than the south

  • Andrew

    Sounds like a finger print. Of soot, though, not CO2!

  • Philip_B

    The real news is the SH hasn’t warmed at all over the satellite period. If anything there has been a slight cooling.

  • MattN

    So, it’s northern hemisphere warming, instead of global warming. Right?

    Agreed on the soot. I blame China. Seriously, they have no standards, and don’t seem to care.

  • Bob Tisdale

    Before you conclude that soot is the culprit, note the correlation between the hemispheric temperature difference (NH minus SH) and the AMO.

    Unsmoothed:

    i30.tinypic.com/23mn96c.jpg

    Smoothed:

    i30.tinypic.com/mafpm0.jpg

  • Andrew

    Bob Tisdale, interesting point, however, 1. we are speaking of the satellite data. 2. AMO as I understand it is detrended temperatures from somewhere in the Atlantic, and I think that it is well established that the apparent roughly 60 year cycle in all three data sets is of varying amplitude. It maybe that what you have done is somewhat like detrending revealing a strong cycle in the data by removing from it a trending data set with a weaker cycle. I hope that didn’t just go way over your head, becuase I barely understood it! It seems to me that the best explanation for the NH lower troposphere warming more than the SH is that there is a radiative forcing effect present there that is weaker/non existent in the SH (that is, soot). I’m having troubling seeing how an oscillatory mode could make one hemisphere warm faster than the other.

  • Bob Tisdale

    Andrew: When you included the statement in your post, “I hope that didn’t just go way over your head,” you were speaking down to me, which started us off on the wrong foot. But that aside:

    I have no idea why you would begin with a note that you’re discussing satellite data. I understand that UAH MSU in Warwick’s graph is satellite data. My previous post was intended to bring a longer term temperature record into the discussion, so that you could consider possibilities other than soot. The blue curves in my graphs are the same variable as the one Warwick posted above (the difference between NH and SH temperature anomalies) except that the ones I posted goes back to 1850. Mine use a different source, the Hadley Centre, since the MSU data only go back 30 years, but basically they’re the same. Those graphs illustrate the findings of multiple studies: that the AMO impacts northern hemisphere temperatures.

    For the sake of the following, let’s forget about differences in albedo relating to hemispheric land to ocean surface area ratios, something else your soot hypothesis overlooks.

    The Atlantic Multidecadal Oscillation is calculated by subtracting global SST from the entire North Atlantic SST, not just “somewhere in the Atlantic”. Assume for example that the North Atlantic represent 20% of the surface area of the northern hemisphere. If the North Atlantic temperature rose 0.5 deg C over the last 33 years (a little longer than the satellite temperature record) above and beyond the rest of the oceans due to natural causes (thermohaline circulation), wouldn’t the measurement of that higher North Atlantic SST (or that greater lower troposphere temperature over the North Atlantic) impact the calculation of northern hemisphere temperature? And wouldn’t a warmer North Atlantic provide additional heat to NH land areas when SSTs are greater than LST (winter) and less cooling when SSTs are lower than LST (summer)?

    Here are two links to discussions of the AMO. The first is from the RealClimate glossary. Gavin et al state the AMO contributes significantly to NH temperature anomaly.

    www.realclimate.org/index.php?p=38

    The second is a Knight et al paper that quantifies AMO contributions to NH and Global temperature. Assuming the paper is right, it’s not as much as RealClimate claims.

    holocene.meteo.psu.edu/shared/articles/KnightetalGRL05.pdf

    Regarding your comment on cycles: My AMO vs Hemispheric Temperature Difference graphs simply illustrate that the two cycles are coincidental over the past 158 years. If you take into consideration the impact of other natural variables that impact temperature–stratospheric volcanic aerosols (DVI), solar irradiance(TSI), El Nino/Southern Oscillation (ENSO)–the correlation isn’t bad. Can you provide a graph of data for 158 years, supported by studies, that indicates the same for soot? Soot might contribute to the hemispheric temperature difference, but the AMO is one of the significant drivers.

    Still having trouble “seeing how an oscillatory mode could make one hemisphere warm faster than the other”? Think of the AMO as a thirty-year-long El Nino in the northern hemisphere. Currently, we’re probably a couple of years past the peak of the AMO warm cycle.

    Regards

  • Andrew

    Bob Tisdale, hi, sorry if some stupid statements in my last post offended you. I have no tact. Anyway, the reason I’m harping on looking at the satellites versus the surface is because there is rather strong evidence that latter are at least to some degree contaminated by land use effects. I suppose I get what you are saying about AMO being like a long period El Nino in the Northern Hemisphere. I acknowledge you may be on to something with this idea, but what is still bothering me is that AMO is supposed to only effect one hemisphere-and don’t think I’ll believe RC about this either. I still think that what you have found is mostly result of the slightly weaker cycle in one hemisphere than the other, essentially making one a bit like a trend line being removed from the other.

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