Is 0.5 C above average a normal deviation range?

Question

I'm blocked from a similar question, so I'll post it again here where open dissent and alternative views can be expressed.

I did a little analysis of the GISS temperature dataset. I computed the Standard Deviation of the average global temperature from 1880 - 1909 (30 years). I got 0.146 C.

The most recent 12-months (2/2007 - 1/2008) is 0.5 C above the average computed between 1951 - 1980. So could the current 0.5 C above average be merely considered a normal deviation range?

Answer 1

Changes of .5'C are not uncommon even during an interglacial period. What is "normal" is subjective, and really doesn't mean anything.

Answer 2

Oddly enough he's unblocked me (go figure).  His question was half about standard variations in the temperature range and half about what groups like NASA use as the "average" reference point.  He feels they're trying to be deceptive, though I can't figure out why.  Here was some of my answer:

"1) That depends on how you define "normal".  The only time the planet's temperature has changed at this rate is when it's entering or exiting an ice age.  Since we're currently in a warm period, I would say no, in no way is the current climate change "normal".

2) The "average" is an arbitrary value.  NASA picks 1951-1980 as its average because it yields a nice round number of 14°C.  The "average" is just a reference point.

4) No, as stated in point #2, the reference period is arbitrary.  The rate of change has nothing to do with the reference point, and changing the reference point in no way alters one's perception of the rate of warming (steepness of the graph)."

He's really grasping for straws in this question.

Answer 3

Ken someone keeps reporting questions and answers about certain topics and getting them deleted, even while questions and answers from the alternative viewpoint on the same topics are allowed.....

The MWP for example.....   Posts that point to reconstructions using proxy data remain while posts that point to evidence of what grew when and where are removed......

Posts citing Mann and Hansen remain, while posts citing Bryson and Lamb, do not - which itself says something since Lamb was to climate science what Mendeleev was to chemistry.

Someone on your "side" is reporting questions and answers with which he disagrees rather than just trying to argue his own point of view.

It's more difficult to do that if you're blocked.

It has to be a regular so that limits it to about a half dozen of you.

If you think you're right, why not just argue the point instead of trying to get the other side's arguments silenced?

Answer 4

No, not when the temperature increase coincides with a dramatic increase in atmospheric carbon dioxide.  CO2 continues to affect climate for 1000+ years, so we have to be very careful about what we set in motion.

Although some people seem to be lulled into a false sense of security by the PR slogan "the climate has changed naturally in the past", the evidence of past climate change associated with CO2 increases confirms that we can't take the risk lightly:

Climate sensitivity constrained by CO2 concentrations over the past 420 million years

http://www.nature.com/nature/journal/v44...

"A firm understanding of the relationship between atmospheric carbon dioxide concentration and temperature is critical for interpreting past climate change and for predicting future climate change1. A recent synthesis2 suggests that the increase in global-mean surface temperature in response to a doubling of the atmospheric carbon dioxide concentration, termed 'climate sensitivity', is between 1.5 and 6.2 °C..."

As for the results of such levels of natural greenhouse gas warming in the past:

http://www.aip.org/history/climate/co2.h...

It was less reassuring to notice what the climate had looked like in certain ancient times when CO2 had stood at a high level... a level that humanity would eventually reach if we went on burning all available oil and coal. The Earth had been virtually a different planet, with tropical forests near the poles and sea levels a hundred meters higher. Worse, as one group pointed out, unchecked emissions seemed bound to bring not only "a warming unprecedented in the past million years," but changes "much faster than previously experienced by natural ecosystems..."(57)

It takes a while for expanses of ice as massive as the Greenland ice sheet to melt, but keep an eye on it in 2009 or 2010 when the next El Nino weather influence, plus the underlying trend of global climate warming, promises to set a new record for global temperatures.  Already there is evidence that the consequences may be coming faster than many scientists (such as last year's IPCC report) predicted:

"Instead of sea levels rising by about 40 centimetres, as the IPCC predicts in one of its computer forecasts, the true rise might be as great as several metres by 2100. That is why, they say, planet Earth today is in 'imminent peril.'"

http://www.heatisonline.org/contentserve...

I don't think that using any 12 month period for comparison has any validity since normal year to year weather variations due to the Eln Nino Southern Oscillation can throw individual years hotter or colder, but using a 5 year average takes most of that noise out of the data:

http://www.columbia.edu/~jeh1/mailings/2...

So the fact that we've only seen the first degree of warming over the past 100+ years is no consolation, since we know the outcome of greenhouse gas warming in the past, and there's no end in sight to our emissions or to the warming that will result.