Russ Steele
The warmers in Sacramento are all worried over a 2 degree increase by 2100, which could cause a tipping point, bringing the world we know it to an end. Yet, we know from paleoclimate records the Sierra was 2-3 degrees warmer in the past, and now we find out the Great Plains were also 2 degrees hotter than today, and that the mean temperature fluctuated over 10 degrees Fahrenheit. And we are still here?
Today Science News Reports:
While temperature records dating back thousands of years already exist for certain regions of the United States, like the East Coast and the Northwest, no such record exists for the North American Great Plains. But now, a Baylor University researcher along with a team of scientists has developed a new method to measure temperature fluctuations in the Great Plains, creating a temperature record for that area of the country dating back 12,000 years.
ooo
In the Great Plains, Nordt found the annual mean temperature fluctuated about 10 degrees Fahrenheit over the last 12,000 years. Between 12,000 and 7,000 years ago, the annual mean temperature was significantly cooler than what it is today, Nordt said, even though the earth was coming out of an ice age and the sun's intensity on earth was steadily increasing. From 7,000 to 5,000 years ago, temperatures finally warmed to the point that it was about 2 degrees hotter than it is today. It has since gradually declined to present day temperatures.
"The results really surprised us, especially between 12,000 and 7,000 years ago," Nordt said. "Earth temperatures should have been getting warmer during that time, but they weren't. We concluded it was caused by negative feedback from the melting glaciers. The ocean water temperature was colder because the glaciers were melting. That, in turn, caused temperatures to drop."
Nordt said the sun's intensity on earth is the main reason why temperatures generally warmed over the last 12,000 years, but that intensity is now decreasing. Yet temperatures are not decreasing.
Science Daily has the rest of the above story.
I am a little concerned about the last paragraph above. The sun is now more active than in the last 100 years. The sun's visible output has not changed much, but the total energy has been steadily increasing over the last 100 years. This output impacts the number of cosmic rays striking the earth and may be connected to cloud formation. A highly active sun limits the number of cosmic rays reaching low altitude regions on the earth, where they promote highly reflective cloud formation. This could account for the rising temperatures, fewer reflective clouds, more sun reaches the surface, increasing temperatures. More details on this process can be found in my paper on the return of the Dalton Minimum, which can be downloaded from the SESF web site.
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