Minority report: 50 year warming due to natural causes: 06/08/10 By Roy W Spencer, PhD

Minority report: 50 year warming due to natural causes

Minority report: 50 year warming due to natural causesPosted on June 7, 2010 by Anthony Watts  http://wattsupwiththat.com/2010/06/07/minority-report-50-year-warming-due-to-natural-causes/

Warming in Last 50 Years Predicted by Natural Climate Cycles

by Roy W. Spencer, Ph. D.

One of the main conclusions of the 2007 IPCC report was that the warming over the last 50 years was most likely due to anthropogenic pollution, especially increasing atmospheric CO2 from fossil fuel burning.

But a minority of climate researchers have maintained that some — or even most — of that warming could have been due to natural causes. For instance, the Pacific Decadal Oscillation (PDO) and Atlantic Multi-decadal Oscillation (AMO) are natural modes of climate variability which have similar time scales to warming and cooling periods during the 20th Century. Also, El Nino — which is known to cause global-average warmth — has been more frequent in the last 30 years or so; the Southern Oscillation Index (SOI) is a measure of El Nino and La Nina activity.

A simple way to examine the possibility that these climate cycles might be involved in the warming over the last 50 years is to do a statistical comparison of the yearly temperature variations versus the PDO, AMO, and SOI yearly values. But of course, correlation does not prove causation.

So, what if we use the statistics BEFORE the last 50 years to come up with a model of temperature variability, and then see if that statistical model can “predict” the strong warming over the most recent 50 year period? That would be much more convincing because, if the relationship between temperature and these 3 climate indicies for the first half of the 20th Century just happened to be accidental, we sure wouldn’t expect it to accidentally predict the strong warming which has occurred in the second half of the 20th Century, would we?

Temperature, or Temperature Change Rate?
This kind of statistical comparison is usually performed with temperature. But there is greater physical justification for using the temperature change rate, instead of temperature. This is because if natural climate cycles are correlated to the time rate of change of temperature, that means they represent heating or cooling influences, such as changes in global cloud cover (albedo).

Such a relationship, shown in the plot below, would provide a causal link of these natural cycles as forcing mechanisms for temperature change, since the peak forcing then precedes the peak temperature.
                                                                     

Predicting Northern Hemispheric Warming Since 1960
Since most of the recent warming has occurred over the Northern Hemisphere, I chose to use the CRUTem3 yearly record of Northern Hemispheric temperature variations for the period 1900 through 2009. From this record I computed the yearly change rates in temperature. I then linearly regressed these 1-year temperature change rates against the yearly average values of the PDO, AMO, and SOI.

I used the period from 1900 through 1960 for “training” to derive this statistical relationship, then applied it to the period 1961 through 2009 to see how well it predicted the yearly temperature change rates for that 50 year period. Then, to get the model-predicted temperatures, I simply added up the temperature change rates over time.

The result of this exercise in shown in the following plot.

What is rather amazing is that the rate of observed warming of the Northern Hemisphere since the 1970’s matches that which the PDO, AMO, and SOI together predict, based upon those natural cycles’ PREVIOUS relationships to the temperature change rate (prior to 1960).

Again I want to emphasize that my use of the temperature change rate, rather than temperature, as the predicted variable is based upon the expectation that these natural modes of climate variability represent forcing mechanisms — I believe through changes in cloud cover — which then cause a lagged temperature response.

This is powerful evidence that most of the warming that the IPCC has attributed to human activities over the last 50 years could simply be due to natural, internal variability in the climate system. If true, this would also mean that (1) the climate system is much less sensitive to the CO2 content of the atmosphere than the IPCC claims, and (2) future warming from greenhouse gas emissions will be small.

http://wattsupwiththat.com/2010/06/07/minority-report-50-year-warming-due-to-natural-causes/

Global Warming Myths Debunked – Great Lakes Freeze Over

Lake Superior is freezing over

7 03 2009

Lake Superior last froze over in 2003. It has now, again, frozen over. The frequency of freeze overs has historically been around once every 20 years. Now, in the last decade, we have seen two freeze overs.

The picture below is a beautiful satellite photo of Lake Superior from yesterday. With the well below freezing temperatures seen over the region Thursday night (-20 F), any isolated open water could have frozen.

Lake Superior satellite image

The NWS in Marquette MI writes:

Due to the recent cold spell and below normal temperatures for much of the winter of 2008-2009, ice covers nearly all of Lake Superior. Only small areas of open water remain. This image was taken on Tuesday, March 3rd. If arctic air does not return in the next couple of weeks, it is likely that this will be the day of maximum ice cover on Lake Superior for this winter as warmer weather and periods of stronger winds through the end of this week will cause open water areas to expand. Click on the image to view a higher resolution satellite picture (image is large — just under 1mb).

http://wattsupwiththat.com/2009/03/07/lake-superior-is-freezing-over/

Lake Superior will freeze completely over approximately once in 20 years. When looking at past statistics ice coverage is measured in percentages. According to the Great Lakes Aquarium, Lake Superior froze over nearly 100 percent in 1996 96 percent in 1994 and about 95 percent in 1972. The last records of complete ice coverage on the big lake is 1979 and 1962.

http://climate.umn.edu/doc/journal/superior030603.htm

Published March 6, 2003

HOUGHTON, Mich. — Record-shattering cold temperatures threaten to freeze massive Lake Superior’s surface for the first time in more than two decades.

 

Great Lakes Freeze For First Time in More than a Decade

Three Great Lakes freeze over

 

 

A month of frigid weather leads to 24-inch icecap

Reuters News Service, March 12, 2003

TORONTO  Three of North Americas Great Lakes  Lake Huron, Lake Superior and Lake Erie  have frozen over for the first time in nearly a decade after icy weather lasting more than a month, experts at Environment Canada said on Tuesday.

A month of temperatures below minus 4 Fahrenheit has caused an ice blanket averaging as much as 24 inches on the lakes, creating problems for shipping companies and ferries.

“The large lakes freeze once every decade,” said John Falkingham, chief of forecast operations, at the Canadian Ice Service, which is part of Environment Canada. “A sustained long, cold spell causes such an extensive ice cover.”

MINUS 13 DEGREES

That frigid weather continued into March. Last week, the temperature fell below minus 13 Fahrenheit in southern Ontario, the coldest March in a century, according to Environment Canada.

The cold weather has affected the St. Lawrence Seaway, which will now open on March 31, almost a week behind schedule, said Ivan Lantz, director of marine operations for the Shipping Federation of Canada, an organization of ship owners and agents involved in the overseas trade.

“My estimate is that before the 15th of April, shipping is going to be very difficult,” Lantz said.    http://www.heatisonline.org/contentserver/objecthandlers/index.cfm?id=4240&method=full


 

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