This is a rather welcome bit of data that pins down the proper time frames alluded to in my many postings on the driving role of ocean temperature as a climate control factor. My investigations had led me to the acceptance of ocean surface temperature as the forcing agent rather than the reverse as was been argued by the global warming crowd.
I had identified the Arctic as the key problem that needed to be understood. The evidence showed that the Arctic had been adding extra heat sufficient to reduce thickness by sixty percent by 2000 from 1959. This warming has continued unabated for the past decade and we are now approaching the final reduction of Arctic sea ice.
The heat input was switched on and it could reasonably be expected to be an annual constant C. The open question was to ask when it may have started.
A switching action was observed around 1970. Hot or cold does not matter because the micro adjustments are what we actually experience. In this case, it meant more warm water began finding its way into the Arctic .
This means that on average, the Arctic began losing up to 2% of its original ice every year. However since the effect is non linear, the percentage of ice loss accelerates toward the end rather dramatically. We are now in the dramatic phase. Look at the chart and recall that the summer months were even stronger. This curve has left the linear down trend channel and we have now entered the visible ice breakup zone as full collapse sets in.
For the record, this phenomenon has nothing to do with atmospheric warming as a cause. Rather we have quite the reverse. A change in the current system has apparently warmed the Northern Hemisphere and cooled the Southern with all the attendant variations. The take home lesson is that if you hope to understand historic climate trends, it is necessary to start with the ocean.
Past Ocean Cold Snap More Dramatic Than Thought
By Wynne Parry, LiveScience Senior Writer
24 September 2010
Though climate change has been warming the oceans, several temperature dips have also occurred. And now scientists have found that one such cold spell, which happened around 1970, was more dramatic than previously thought.
Over the course of the 20th century, the Earth's surface has warmed by more than 0.9 degrees Fahrenheit (0.5 degrees Celsius), according to the United Nations' Intergovernmental Panel on Climate Change. However, the warming in the oceans, particularly in the Northern Hemisphere, has been less straightforward.
World average sea surface temperatures plummeted around 1945 and then again around 1970, before continuing to warm, data has shown. The first dip is believed to be an anomaly, caused by problems with the instruments used to measure it. New research indicates, however, that the second cold snap was both quite real and quite significant.
The study found that between 1968 and 1972, the sea surface temperature of the Northern Hemisphere dropped by about 0.54 degrees F (0.3 degrees C), a change so dramatic that it cannot be explained by natural cycles in ocean temperature or cooling caused by aerosols, small particles of pollution, which can reflect sunlight and cool Earth's surface.
Unlike data for the earlier drop, evidence of cooling temperatures around 1970 exists in numerous measurements of sea surface temperatures. The researchers liken the speed of the cooling to "abrupt climate change," which the IPCC describes in a 2007 report as a regional change of several degrees Celsius within several decades. On the other end of the scale, climate change caused by astronomical factors, such as changes in the Earth's orbit, progresses over thousands of years, according to the report.
The most marked cooling during this period occurred in the North Atlantic Ocean , and the authors speculate that it may be connected to a decrease in salinity (the salt content of the ocean) there in the late 1960s and early 1970s. This is the only potential cause the researchers offer.
Meanwhile in the Southern Hemisphere, surface temperatures rose steadily during the second half of the century, according to the report. Researchers were already aware that the Southern Hemisphere had warmed more than the Northern Hemisphere during this time, however, this new study revealed the sudden nature of the gap between the two hemispheres, according to study researcher David Thompson, an atmospheric scientist at Colorado State University
Most previous work "is based on 'smoothed' versions of the data, and thus the suddenness of the difference around 1970 was largely overlooked," he told LiveScience in an email.
Thompson and the other researchers used a method that reduced year-to-year variation in temperatures caused by variation in air circulation; the El Nino Southern Oscillation, a periodic ocean−atmosphere fluctuation that affects weather around the globe; and volcanic eruptions, which like humans, spew potentially cooling aerosols into the atmosphere. These short-term phenomena can obscure significant events, such as this sudden, northern cooling, the researchers wrote in the Sept. 23 issue of the journal Nature.
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