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|Subject: Re: How warm was 2010?||Date: 12/31/2010 7:26 PM|
|Author: putnid||Number: 547300 of 708777|
So typical of Watts...he kinda left out a few details. Note that his whole piece is based on the Greenland ice core data. From that, he insinuates that the entire planet was warmer 10,000 years ago.
We're talkin' about the "Holocene Climatic Optimum":
The Holocene Climate Optimum was a warm period during roughly the interval 9,000 to 5,000 years B.P.. This event has also been known by many other names, including: Hypsithermal, Altithermal, Climatic Optimum, Holocene Optimum, Holocene Thermal Maximum, and Holocene Megathermal.
This warm period was followed by a gradual decline until about 2,000 years ago.
The Holocene Climate Optimum warm event consisted of increases of up to 4 °C near the North Pole (in one study, winter warming of 3 to 9 °C and summer of 2 to 6 °C in northern central Siberia). Northwestern Europe experienced warming, while there was cooling in the south. The average temperature change appears to have declined rapidly with latitude so that essentially no change in mean temperature is reported at low and mid latitudes.
In terms of the global average, temperatures were probably colder than present day (depending on estimates of latitude dependence and seasonality in response patterns). While temperatures in the Northern Hemisphere were warmer than average during the summers, the tropics and areas of the Southern Hemisphere were colder than average which comprised an average global temperature still overall lower than present day temperatures.
This climatic event was probably a result of predictable changes in the Earth's orbit (Milankovitch cycles) and a continuation of changes that caused the end of the last glacial period.
The effect would have had maximum Northern Hemisphere heating 9,000 years ago when axial tilt was 24° and nearest approach to the Sun (perihelion) was during boreal summer. The calculated Milankovitch forcing would have provided 8% more solar radiation (+40W/m²) to the Northern Hemisphere in summer, tending to cause greater heating at that time.
Ah, the games the skeptics play. Where are we today in relation to the Milankovitch cycles? We should be cooling appreciably.
The planet grows warmer. Go figure.
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