mandag, november 07, 2011

State of climate - an update

It's been some time since I wrote my piece on the state of climate and I've hopefully grown wiser ever since. I would like to share some simple observations first.

In the state of climate article I showed you this sketch from a National Geographic article from the mid 70's (I don't trust the modern products all too much, so it's nice with some counterbalance from a time, when people still had respect for 'objective' science).

I've now superimposed my graph of solar cycle length on that sketch (That would be the red line). And you may notice that they seem somewhat in tune. Now have a look at this graph:

If you click on the images you'll get an enlargement. Please note the dates of polynomic intersection between the AMO (North Atlantic) and the PDO (North Pasific). I get 1934, 1968 and 1998. I also believe, that if the data had reached further back in time you would have been able to locate an intersection around 1900-1910. 

There's some history to this: The Titanic sunk by ice berg 1915, 1934 warmest year in the US thermal record, 1976 marked the year of the great pacific climate shift (changing PDO), the great El Nino of that previous year made 1998 the hottest year on the global record, and scared the easily scared alarmists out of their wits. Compare with the modern global temperature scare product (on the left) and viola, how could anybody miss these striking 'coincidences'. Well the answer is: it takes an enormous amount of bias.  Compare the steep climb of late thermometer record with the satellites gentle hump:

Check also the previously mentioned years of AMO/PDO intersections with some Arctic history: 

Warming Arctic Climate Melting Glaciers Faster, Raising Ocean Level, Scientist Says - “A mysterious warming of the climate is slowly manifesting itself in the Arctic, engendering a “serious international problem,” Dr. Hans Ahlmann, noted Swedish geophysicist, said today. - New York Times, May 30, 1937

“The United States and the Soviet Union are mounting large-scale investigations to determine why the Arctic climate is becoming more frigid, why parts of the Arctic sea ice have recently become ominously thicker and whether the extent of that ice cover contributes to the onset of ice ages.” - New York Times, July 18, 1970  

Arctic warming has become so dramatic that the North Pole may melt this summer (2008), report scientists studying the effects of climate change in the field. “We’re actually projecting this year that the North Pole may be free of ice for the first time [in history],” David Barber, of the University of Manitoba, told National Geographic News aboard the C.C.G.S. Amundsen, a Canadian research icebreaker. - National Geographic News, June 20, 2008 

Of course the North Pole is not melting catastrofically and it is now reported, that sea ice has been refreezing at 40% the average rate (Sat history rate that is) during  this October.

Idealised sketch showing typical areas of low pressure 
thermal expansion, as well as high pressure migration routes 
out of the arctic.

As the pole heats up due to the warmer waters arriving in the region (forced by solar insolation in the tropics and possibly modulated by cloud and galactic cosmic rays), convective expansion pushes cold airmasses to the south over the continents (colder winters warmer summers in the interior). Eventually the cooler drier northern airmasses reaches tropical waters as they move south east where they fascilitate an enhanced Hadley circulation and upwelling regime. The northern warming cools the southern regions. As the south gets colder so, eventualy, do the hot waters which are pushed to the poles at the western plate boundaries. Eventually the north cools. Possibly solar forcing and magnetic fields (both the Suns and the Earths) modulate the polar atmosphere in various ways: cloud, moisture, temps.

The water temperature in the four regions marked in red  determines the level of thermal expansion around the region. In combination with the state of the polar cells pressure/temperature this determines where Arctic breakouts happen (blue arrows) and how intense the events. The PDO and AMO patterns are characteristics of this combined ocean/atmosphere behaviour and is actually an expression of a comprehensive northern hemosphere climate state which modulates the route of the northern jet stream. It defines the polar vortex and the meandering of high pressure systems. As this system feeds back on itself it oscillates between the phases shown in figure 2. The keen observer may notice, that the AMO seems to warm and cool with the cycles of the sun. While the PDO seems to respond to the AMO. And the PDO seems to 'regulate' global temperature. So there's a delay of about 15 years from the warming AMO until the Pasific starts cooling 'way down', which in turn starts cooling the AMO. The 'global' cooling is setting in right about now.

The danish meterological institute has a Java animation (Bottom of the page) simulating atmospheric circulation for the next week. Running this regularly, you can study the high pressure migration, and  the thermal expansion (low pressure) areas and the interaction between them. 
As the North Atlantic atmosperic thermal expansion becomes stronger than the Pasific thermal expansion cold air is pushed between them and the Atlantic wins: the tropical Pasific cools because cooler drier anticyclones enhances Hadley circulation and cold water upwelling. This drives hot water masses north (and south) at the west Pasific plate boundaries: the North Pasific warms. Eventualy the North Pasific will start pushing cold air masses into the North Atlantic creating blocking and cooling. The two oceans move in phase. During the next 20 years a warming North Pasific will graduately cool the North Atlantic.

Obviously this is a highly idealised schematic: a multitude of parameters most of them probably unknown modulate the highly complex climate system. Nothing is for sure!

Ocean temperature anomalies presented by NOAA as of October 26, 2011. 
Showing a cold PDO and a positive NAO.

As I see it, we seem to be in a somewhat simular situation as around World War II, where Hitlers armies perished in Russia due to extremely cold winters, and Scandinavia was hit by severe ice winters. While at the same time the Arctic was melting.

When we look at solar cycle length, it would seem that the recent warming in the 90's was somewhat stronger than the warming in the 30's. However, the present solar cycle lengths should provide a strong cooling effect... all in all we will probably be somewhere near 70's temperatures in roughly 25 years - somewhere around 2035. A cycle length of 60 years. By then we should have a good grasp on what the real effect of co2 looks like.

Oh I should mention, the colder, drier polar airmasses moving on the tropics should generate a lot of downpour. This would spell true in the North as well, as the thermal expansion areas (d)rain away. All this work will remove heat from the oceans, cool the planet and grow the glaciers by a small amount.