This item points out that the two historic warm eras were matched by cold waters in the tropical Pacific. This is my link to the Global Counter Current. It is the only mechanism in place able to actually link the two and balance them off. That they were balanced is important.
First, it excludes the sun and local events as drivers. It tells us that a change in the global ocean circulation of major proportions chilled surface waters in part of the Pacific and that the
Atlantic added two degrees in warmth (earlier post). This actually is huge and informs us of about how much change can take place.
The present warming of the
Arctic suggests that this switch is once again under way and will slowly develop over the next century or two. The historic strength of the warming effect is such that it might well also explain the Bronze Age optimum.
As I have also pointed out in an earlier post, it is pretty clear that we have a 1200 year climate cycle that apparently operates to balance the two hemispheres. We can tell this because the actual switching event is abrupt enough to be noticed as an abrupt chilling that freezes rivers. The warming also has measurable peaks but is less obvious.
It appears that the counter current slows. This permits an expansion of warm surface waters in the
Atlantic and an increase in temperature. The result is more warm water been pushed into the Arctic. It also allows the expansion of cold Antarctic waters into the South Pacific. For the present we are assuming these are all surface waters. The appearance of a global balance is in evidence.
Last year I was looking to the currents to explain some of the global climate issues. Today with the CO2 hypothesis effectively disproven, at least with current CO2 levels, it leaves water temperatures or other unusual atmospheric inputs to argue the case. I now suspect that atmospheric inputs beside solar and ocean temperatures are simply way too ineffective.
However, water temperature is clearly effective and solar variation is rather small and possibly too small. The mistaken assumption was to assume that water temperature had little variation. That is nonsense. The two degree shift by the
Atlantic is a massive change when compared to solar variation.
The bottom line is that climate is driven by sun and ocean surface temperature (and its natural sibling vapor pressure of water). The known variation in climate coincides with the known variation in the surface temperature of the
Atlantic and water temperature drives climate rather than the reverse. This is a classic case of fresh evidence resolving old issues.
Climatic warming in the Northern Hemisphere is taking place because the heat content of the surface waters of the
Atlantic is increasing. We can additionally state that the change averages 0.4 degrees per century or something that appears close. The actual rise may never be abrupt but that may also be only the present indication. The clearing of Arctic sea ice now happening may allow an abrupt temperature rise to take place in the Atlantic over a much shorter time period ending in a stable two degree warmer Atlantic for several centuries.
The connection between global warming as we understand it and rising Atlantic surface temperatures is specific and coincidal and linked to a balancing change of equal apparent strength in the South Pacific. That is the big picture and we have about eight hundred years of good climate to enjoy.
What Explains Past Climate Change?
Was the climate really hotter during medieval times? David Biello reports
Roughly 1,000 years ago,
Europe enjoyed several centuries of balmier average temperatures. Dubbed the "Medieval Warm Period," it was the last time before the present that agriculture could flourish in Greenland. This era also shows yet again that changes to natural systems can drive local climate change—and provided fodder for countless misunderstandings about the nature of present day global warming.
But new research shows that the MWP, as it is affectionately known in acronym-happy science circles, as well as the "Little Ice Age" that almost immediately followed it (and spelled doom for the
Greenland Norse) were likely the result of fluctuations in the sun's strength and the frequency of volcanic eruptions, among other natural causes.
Cores drilled from ancient ice sheets as well as of the coral reef and lake sediment varieties show that at the same time as Europe enjoyed average temperatures as warm as today, the tropical Pacific was unusually cold. This suggests that natural cycles—such as the succession of El Nino and La Nina conditions in the
Pacific Ocean—forced these climate anomalies.
Unfortunately, neither the sun nor other natural cycles can entirely explain the recent warming trend that has brought potatoes back to coastal
Greenland. To date, the only explanation that matches those observations are a concurrent rise in greenhouse gas concentrations in the atmosphere.
CO2 and its peers now are responsible for trapping an extra three watts per square meter of planet. And if that continues, the MWP will end up looking like an ice age.