Is global warming causing global cooling?

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It's called thermohaline circulation, or the ocean conveyor belt, and it is a delicate pattern of circulation within the world's oceans that balances water density gradients generated from surface heat and freshwater entries.

It is an established fact that the ocean conveyor belt regulates climate.  "warm waters around the equator flow northward and bring heat to Northern Europe, while cool waters from the polar region flow southward".  Without the circulation of ocean waters, some regions of the planet where human civilization has been established would no longer be comfortably hospitable to us.

The global warming skeptics who cite a recent downward trend in global temperatures since 2002 may very well be pointing to evidence that global warming is already at work.  Human activity may very well be speeding up a natural cycle that would usually take several centuries to evolve.

The Pleistocene period, an historical era that has lasted roughly for the past 2.5 million years, is marked by cycles of ice ages and warming periods.  The pattern has repeated itself, experts believe from looking at ice core samples, more than 80 times.  Interglacial, or warming periods are marked by increases in plant and animal communities, as marked by the fossil record.  Glacial periods marked extinction events for species not able to adapt to cooler temperatures or unable to migrate from advancing glaciers.

The Holocene period, the only era after the Pleistocene, is simply the latest 10,000 year warming period.  Some experts do not delineate between the Pleistocene and Holocene and state simply that the pattern of glacial and interglacial periods has not yet been broken.

The distinguishing fator that makes the Holocene period different from the Pleistocene is the introduction of human civilization.  Contrary to all of the other glacial periods in the Pleistocene, now humans have the capacity to influence some of the factors to speed along the cycle of glacial-interglacial.

What happens if the thermohaline circulation is disrupted?  Can humans disrupt the circulation pattern in the world's oceans?  NASA states: "If the poles warm, it is possible that melt water from glaciers and the polar ice cap can shut off this circulation and interrupt this circulation system. The melt water is fresher and hence less dense than the ocean water it melts into, and thus the melt water will tend to accumulate near the surface. This layer of fresh water acts as an insulating barrier between the atmosphere and the normal ocean water. The water from the tropics can not release its heat to the atmosphere, and the circulation loop is interrupted. The mechanism has a positive feedback potential in that if the ocean circulation slows, then even less heat will make it to the higher latitudes re-enforcing an effect that will cool the climate at these higher latitudes". 

In plain English, if we melt our glaciers quicker than they would normally in natural cycles, and we release enormous amounts of cool freshwater into the ocean conveyor belt, then global temperatures will plummet faster than natural systems can adapt.  By adding more CO2 into the atmosphere, we are speeding up a cycle that has shown its consistency over the past 2 million years.  (CO2 is a greenhouse gas; greenhouse gases trap heat)

Global warming deniers who simply state that the earth is cooling as their sole data for denial do not realize that they are making the case for global warming.  After warming and melting ice that is frozen on land, earth's temperature drops because the warm ocean currents that regulate our temperatures are disrupted.

Why then were ocean temperatures so warm this summer.  I don't know.  Watch this video from NASA to see what happens to the Atlantic Ocean's circulation when glaciers on Greenland melt.  The whole circulation pattern stops and warm water is backed up along the Eastern U.S. coast.  Perhaps wild fluctuations become the norm until an equillibrium can be established.  Regardless, the idea that global warming can cause global cooling in the long run should make us think about whether both sides of this debate are making the same case.

For more info:   The cryosphere; Wikipedia. Cryosphere: Earth's frozen assets; NASA.

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