One purpose of science is to determine the Cause and Effect of a system. When it comes to climate, that can be difficult as one change can cause so many other changes. For instance, a change in water temperature causes a change in atmospheric CO2 levels. That could cause a feedback effect, but it isn’t the cause of the change itself.
Last week I showed that the seasons in the Northern Hemisphere have the biggest impact of the global temperature average. I also showed how the climate sensitivity could be determined from changes in the summer energy of the Northern Hemisphere (NH). I might have gotten ahead of myself with that one. So I will add this article in to show how significantly the current climate of the Earth has been determined by the amount of energy the NH receives from the sun.
The last glacial (ice age) was ending about 17,000 years ago. The cause of its end was an increase in the solar energy the NH was getting from the sun during the summer months. This resulted in what is referred to as the Holocene Interglacial. That is the warm period that we are currently living in. Here is a chart that shows the temperature of both poles and the amount of energy the NH has been getting during the summer months.
This shows that well before the temperature started to increase in either hemisphere, the amount of energy in the NH started to increase during the summer months. Since the peak summer energy levels in the NH started dropping 9,000 years ago, the NH has started cooling. This is shown in all of the NH ice core data. That is why I show a NH ice core as the chart on the header for this website.
That the NH has been cooling for the past 6,000 years has found new supporting evidence in a recent article (Jakobsson, 2010) that states in the abstract:
“The combined sea ice data suggest that the seasonal Arctic sea ice cover was strongly reduced during most of the early Holocene and there appear to have been periods of ice free summers in the central Arctic Ocean.“
The ice core data and this most recent article all point to the early Holocene being warmer in the Arctic than it currently is. A period of warmth like that would have caused more ice melt in Greenland than what is currently taking place. Almost all claims of the “dangers” of global warming existed in the early Holocene. What is proposed as being unnatural, just happened a short few thousand years ago.
The counter claim to that would be, “now CO2 levels are high.” Here is my very simple response to that.
CO2 levels have been increasing (due to warmer ocean temperatures) for thousands of years. The strong forcing factor of NH summer energy levels has been cooling the NH which has caused the summer Arctic ice to return in the same period that the CO2 levels have been rising. Much like I have shown before, CO2 has never been able to prevent the Earth from cooling. The increasing CO2 levels for the past 10,000 years have not prevented decreasing NH temperatures. Nor is there any indicator that they will be able to in the future.
Vostok Ice Core: Temperature and CO2.
Taylor Ice Dome: CO2
NGRIP: Greenland Ice Core
Northern Hemisphere: Summer Insolation