Guest essay by Tony Brown
Some readers might recall my recent article ‘The Long Slow Thaw?’
In this I reconstructed Central England temperature to 1538 from its current instrumental date of 1659.
I was surprised by two notable periods of warmth around 1630 and 1530. I am indebted amongst other material, to Phil Jones excellent book ‘Climate since 1500 AD’ plus such books as Le Roy Laduries’ Times of feast times of famine’ which confirm that these were indeed warm periods.
The graph below is from my article but to it has been added the official co2 levels. CET is seen by many scientists as a reasonable but by no means perfect proxy for Northern Hemisphere and Global temperatures.
Please note that the graphing package somewhat inflates the warmth in the decade around 1540, although my recent research- which will extend CET to 1498-demonstrates that the period 1500 to 1540 does indeed appear to be around as warm as the warm period in the recent CET period ending around the year 2000, characterised by the distinct hump.
Also from a graphing viewpoint it is debatable as to where the CO2 line should be placed. I chose to place it around the black trend line as the CO2 and temperature trend line probably needs to start together at the same place. This also provides clarity and context to the graphic although others might feel the CO2 line should be placed elsewhere.
However these are all nuances and the point I want to put over is that temperature is highly variable throughout the CET record -which is at variance to Dr Mann’s (global) work and the assertions of the Met office. This is despite a constant level of co2 until around 1900. The temperature decline since 2000 as the CO2 line rises ever further is especially intriguing.
Does it demonstrate that once you get to around the 300ppm level that the law of diminishing returns sets in as the logarithmic curve of CO2 versus temperatures takes effect? Does it illustrate nothing and the current downward CET slope is merely a blip that will increase sharply again as more CO2 is added?
The apparent effects of adding additional CO2 was clearly shown in an article by David Archibald several years ago,
http://wattsupwiththat.com/2010/03/08/the-logarithmic-effect-of-carbon-dioxide/
I merely present my research and findings for comment. An apparent decline perhaps as the logarithmic effect ceases to have any real world meaning? Or merely a hiatus in the ever upwards rise of temperatures since the start of the record in 1659 which may or may not be affected by CO2 and radiative physics?
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herkimer
You pose some interesting concepts there.
If I can use an analogy, I live in a coastal village that has just had a flood defence wall built. The village has never been flooded but I welcomed it because it could have been many times IF;
The river (we are on an estuary) had been in substantial flood due to prolonged rain
It was an exceptionally high spring tide.
It was no more than an hour either side of the spring tide.
The wind was blowing gale force from the east (heaping up the waves)
There was a low pressure system sitting in the ‘wrong’ place.
If only a few of these factors are in position there is likely to be no problem
Similarly, I think that for extreme conditions such as the little ice age periods to occur we would also need a coincidental set of circumstances-if they dont happen all around the same time the impacts are lessened. They include;
The jet stream stuck in the ‘wrong’ place
A corresponding high pressure feeding in winds consistently from the North or East (in winter)
SST’s at a low temperature
The ‘gulf’ stream to be either diverted or weaker than normal
The AO at a certain stage in its cycle
Solar cycle at a certain stage (few sunspots?)
A substantial La Nina or El Nino
Numerous other factors we know of (such as Volcanoes)
Numereous other factors we don’t know of.
I suspect this last factor is at least as big as all the other factors listed added together.
How all these climate factors interact with each other is nowhere near as certain as the factors that could cause flooding in my village.
That we may discover WHY temperatures rise and fall-sometimes for long enough periods to create an MWP or LIA -I have no doubt we will figure out one day but I think we are an awful long way from that point and your post is as good an explanation as any.
tonyb
tonyb
Good comments . I have been looking into the behaviour of AMO during these solar minimums and it behaves totally different in each case assuming that all our data is correct. In the case of Maunder , AMO was rising during much of the early minimum[for 45 years ] and then dropped for the latter part[1690-1720]. During Dalton , AMO went cold in 1780 or 10 years before the start of the Minimum and then stayed cold well through the minimum all the way to 1850. During the 1880-1910 Minimum it only went negative after 2 low solar cycles or about 20 years after 1880 starting in 1990 to 1926. There appears to be a lag AMO cooling effect that seems to kick in after the solar minimum proceeeds long enough that makes the AMO turn cold or extend longer as we saw with the Dalton case
herkimer
I don’t think I have seen you writing a piece here so I would encourage you to put your thoughts into an article and get some input here.
There is no doubt that sometimes things happen in climate in ways we dont expect. I put CET into 10 year and 50 year anomalies and it is surprising how much the climate shifts up and down sometimes by quite large amounts. Why?
Here is a link to my graphs;
http://climatereason.com/Graphs/
The first few graphs show glacier advances and retreats and they are there in order to provide some context to warming and cooling periods.
Of course the glaciers don’t abruptly retreat or advance in the manner the vertical lines suggest, so the graphic needs to be refined, but it illustrates that it takes time before the glaciers have definitively moved. It may well be that one of the graphs may give you some more clues to the various things you have observed.
tonyb
herkimer says:
May 10, 2013 at 7:46 am
“So the solar minimum was not affecting the Ocean sst.”
If you look in much finer detail you can see many places where the North Atlantic SST’s drop when CET is high, and rise when CET is low: http://1.2.3.13/bmi/i36.tinypic.com/wld5kl.jpg
Probably a southerly jet stream position transports more warmer sea water further north than a northerly jet stream position can. Though incursions of Arctic air may damp the response.
I should imagine that it is seasonally variable, and may correlate better with winter temperatures rather than annual CET, for example the cold winters though the 1770’s where the North Atlantic SST’s are rising, but CET annual is not that cold: http://climexp.knmi.nl/data/tcet.dat
Take a look at temperatures in the 1570’s at the big spike in the reconstructed SST’s:
http://booty.org.uk/booty.weather/climate/1500_1599.htm
URIC LYONS
I appreciate your comments.There can be short term exceptions My comments referred to. a relatively long period or trend of 1600-1715 when solar activity was dropping and went to zero sun spots by 1645 and this continued until 1715.The North Atlantic SST was rising from 1600-1690. CET was mostly in a cold mode except about 1610-1650 when it had a brief warm period .. The Atlantic continued to be in the warm mode after solar sun spot activity went to zero 1645 and never was in the cold mode during Maunder Minimum.but was so after 1720..
@herkimer
The short term behaviour helps explain the long term, that’s why it is worth examining finely. And I’m sure with an general increase in frequency of cold events and decrease in warm events through the 1600’s the trend in N. Atlantic SST should be upwards, and show why SST’s are warmest in the 1670-90’s.
So a few threads back, we were warned about graphing 2 data sets on the same graph without having a proper known relation between the 2 sets. What I’d like to know is why so many insist on using temperature and CO2. Yes, I know they are related….but the relationship isn’t 1:1 it’s logarithmic. So, shouldn’t proper scaling on the right hand side of all these graphs be logarithmic?
Maybe I’m just thinking too much. But then, if you showed CO2 on that kind of scale..there wouldn’t be much to see..
Serendipity
herkimer says:
May 10, 2013 at 7:46 am
“So the solar minimum was not affecting the Ocean sst.”
‘If you look in much finer detail you can see many places where the North Atlantic SST’s drop when CET is high, and rise when CET is low:
http://1.2.3.13/bmi/i36.tinypic.com/wld5kl.jpg‘
Today at WUWT we have a post by Bob Tisdale on Specific Humidity and SST and global land + sea temperatures showing apparent direct linkage. What is interesting is to watch the animation covering the La Nina and El Nino periods especially in the CET versus N Atlantic and Europe area. This shows, at least in this period, that the CET area often responds differently such that we would expect during these times a different temperature. It also shows that using global average data is misguided.
If you look in much finer detail you can see many places where the North Atlantic SST’s drop when CET is high, and rise when CET is low.
One of the NAO’s consequences.
There is a chain of natural variability in the N. Atlantic illustrated here:
http://www.vukcevic.talktalk.net/NA-NV.htm
-Tectonic activity in the N. Atlantic for some unknown reason correlates with sunspot count
– tectonics continuously varies balance of warm and cold currents to the north and south of Iceland.
– where there is strong sea-atmosphere interaction, several hundred of W/m2 of heat is released into atmosphere, cooling warm currents before their down-welling.
– released heat changes atmospheric pressure around Iceland (principal NAO component), altering path of the polar jet-stream.
– the effect of the jet-stream meandering is well understood.
The one climate factor that behaved consistently during the period noted on the graph of this post was Greenland temperatures . During every minimum, the temperatures dropped as measured by oxygen isotope records per Don Easterbrook studies .. In the case of Maunder Minimum, the temperatures started to drop about the same time as the minimum started in1640 and except for 2 very brief warm spikes , it was colder than normal until 1740.. So with the Arctic colder than normal, the solar suspot cycles at zero and a series of at least 8 major volcanic eruptions during the Maunder , the CET tempertures had to drop.. Why AMO or the North Atlantic stayed postive until about 1890 is not clear.?It clearly has its own tempearture driver and cycle . This could have signifigance for us today as the AMO is also still positive, the sunspot cycle is predicted to go to zero or to a lower level and the Arctic is just starting to signs of cooling .I look to the Arctic for cotinued cooling to drive this next cooling cycle from now to 2030.and many more years of negative AO.
herkimer says:
May 11, 2013 at 6:18 am
Why AMO or the North Atlantic stayed positive until about 1890 is not clear.?
It is again to do with Iceland.
AMO is controlled by Suppolar gyre (SPG) , which is driven by mixture of cold and warm currents. The SPG is the engine of the heat transport across the North Atlantic Ocean, it is a region of the intense ocean – atmosphere interaction. Cold winds remove the surface heat at rates of several hundred watts per square meter, resulting in deep water convection. These changes in turn affect the strength and character of the Atlantic thermohaline circulation (THC) and the horizontal flow of the upper ocean, thereby altering the oceanic poleward heat transport and the distribution of sea surface temperature (SST). The SPG’s northern section is made of cold and warm surface currents, follow images in reverse order in this link
http://www.vukcevic.talktalk.net/DStr.htm
Warm current is split by Reykjanes ridge, the larger part loops westward, while minor turns northward via shallow Denmark Strait.
By far strongest part of the cold current is the Arctic outflow along the Greenland’s coast, the route for the southwards drifting icebergs. An iceberg 10-20m above surface would be 90-180m below surface.
Back to the Maunder Minimum; at first many icebergs would be cluttering Denmark Strait, which eventually could have been partially or completely frozen, currents flows in both directions would be impeded to depth of several tens of meters; result:. more warm and less cold currents into the SPG, keeping the AMO high.
VUKCEVIC
Many thanks for the clarification. I like your CET graphs as well and refer to them quite often.
@vukcevic
Considering the influence of the trade winds on ENSO phase, I would suggest that the jet stream latitude is very influential in Atlantic circulation patterns. And given the short term solar forcing on the AO/NAO, the jet latitude should lead the changes in regional SST’s.
Steven Mosher said @ur momisugly May 9, 2013 at 11:42 am
You dont need to know anything about climate history to understand that feeding the plants c02 at will is not a wonderful risk free idea… They might become angry if we stop 🙂
I still say its just changes in the jet stream, the rising temperatures were going their way for awhile but natural changes will now lower them and make them look foolish. THanks for the graph