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Author Topic: Why is the top of the earth warming faster than the bottom?  (Read 3294 times)

Offline CliffordK

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Here is a 10-year average temperature chart by NASA, 1999 to 2009 vs the 1951 to 1980 mean.
http://www.nasa.gov/topics/earth/features/temp-analysis-2009.html


As we all know, heat rises...  but, it doesn't quite work that way with a global map.

While we've been hitting significant 30 year lows for Arctic sea ice, the Antarctic sea ice extent has been running at average, or even slightly above average.
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.recent.antarctic.png

Likewise, with the exception of the Antarctic Peninsula, the Antarctic temperatures have been close to average, and looking at past maps, the Antarctic Peninsula seems to go through phases of warm vs cold periods.

One hypothesis, of course, is that if CO2 is a greenhouse gas, then it would have greater effect in regions with lower humidity due to a wider IR window, and thus its effect is greater at the poles than in the tropics.  However, this doesn't account for the north/south difference.

So, should we be looking for something that man does that would impact the northern hemisphere greater than the southern hemisphere?

Sulfur Dioxide (SO2) has been in the news periodically as an agent that reflects sunlight.  Atmospheric SO2 has been decreasing due to fuel and power plant changes over the last few decades, presumably with greatest impact in the northern hemisphere (however, I don't have data for hemispheric differences at this time).

http://earthobservatory.nasa.gov/Features/GISSTemperature/giss_temperature4.php


One of the things about sulfur dioxide is that it's half-life (a few days) in the atmosphere is shorter than carbon dioxide, and thus has less north/south mixing.  So, one might expect a northern hemisphere pulse would have less effect on the south.

So, the baseline period for the NASA GIS maps (1951 to 1980) was from a peak period in SO2, and a correspondingly cold period in northern hemisphere temperatures.

And, if you look at the full GIS animation , what one finds is that peak northern hemisphere temperatures also occurred in the late 30's and early 40's.

I decided to compare the Sulfur Dioxide to the North Atlantic Oscillation.  I had to shift the charts slightly for them to line up (about + 5 years for the NAO.  I would have expected a slight delay, but I'm attributing it to the Greenland Proxy data collection methods for the SO2 data).  I thought the results were powerful enough to spin off a separate topic.

Sorry for the crude hack-job on the chart.


The point is that there may be some pretty startling effects of an earlier peak, and later reduction in northern hemisphere SO2 levels that could account for much of the hemisphere differences in temperature anomaly distribution.



 

Offline Don_1

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Could the simple fact be that the south has much more ocean, which takes longer to warm, while the north, with a greater land mass, heats that much quicker? That, combined with a greater CO2 concentration which would help retain the heat and the heat generated by large towns and cities may be having a greater effect than we realise. Also the greater area of the southern polar region would reflect more sunlight than the north. And what part might oceanic currents play in this?
 

Offline CliffordK

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Much of Canada and Russia, of course, become snow covered in the winter, when the sun doesn't shine, so albedo may only be an issue in the spring and fall (and summer).

It is a good point that the oceans provide an enormous heat sink, with slow mixing down several hundred feet, perhaps also providing a break between weather patterns between continents.

Is there that great of a north/south CO2 difference?



I see there is a bit of a peak over the northern continents.
Although, this entire scale covers 10ppm, hardly 5 years CO2 accumulation, and it may be misleading because the CO2 concentration always goes up in the summer.  Does the south see higher levels in December?

It is interesting to see the prominence of the Amazon and Congo.
 

Offline CliffordK

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I was thinking today about the differences between the Arctic and the Antarctic.

One of the differences is elevation.  Much of Antarctica is 2000 to 4000 meters in elevation.

Part of the AGW hypothesis is that the CO2 will cause an increase in temperature in the lower troposphere, and a decrease in temperature in the stratosphere. 

Perhaps the high elevation temperatures in central Antarctica are more stable than the low elevation Arctic temperatures due to thinner air.
 

Offline damocles

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From CliffordK:
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Does the south see higher levels [of CO2] in December?

In the Northern hemisphere, the great Northern forests shut down their photosynthesis activities for the harsh winters. At the same time the humans do a lot more fuel burning to keep warm, and for other purposes. Carbon dioxide levels climb from the late autumn, through winter, and reach a peak around mid May, when the trees have their new foliage in full swing and the humans shut off their fires and emerge into the open again.

In the Southern hemisphere, little land, few forests, and we have mainly evergreen trees anyway, mild winters, and few humans. The carbon dioxide monitoring stations show only very small seasonal fluctuations

Compare http://www.csiro.au/greenhouse-gases/ data from Cape Grim in Western Tasmania with the Mauna Loa record http://www.esrl.noaa.gov/gmd/ccgg/trends/
 

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