Uncovering Natural Trends in Hydroclimatology

[Andre]

At last, what we have been waiting for:

http://www.agu.org/pubs/crossref/2005/2005GL024476.shtml

Abstract
Hydroclimatological time series often exhibit trends. While trend magnitude can be determined with little ambiguity, the corresponding statistical significance, sometimes cited to bolster scientific and political argument, is less certain because significance depends critically on the null hypothesis which in turn reflects subjective notions about what one expects to see. We consider statistical trend tests of hydroclimatological data in the presence of long-term persistence (LTP).

Monte Carlo experiments employing FARIMA models indicate that trend tests which fail to consider LTP greatly overstate the statistical significance of observed trends when LTP is present. A new test is presented that avoids this problem. From a practical standpoint, however, it may be preferable to acknowledge that the concept of statistical significance is meaningless when discussing poorly understood systems.

And telling it's conclusion in my own words so not to infringe copyright. Costs 9$ to check if I'm cheating:

The authors conclude that their findings have implications for both science and public policy. The evidence is rather convincing that the planet has warmed in the 20th century. Assuming that the current knowlegde about complexity, long-term persistence, and non-linearity of the climate system is correct, this warming could have been caused by natural dynamics.

The reported trends are real but actually insignificant. This suggests that natural climatic variation may be much larger than assumed; large enough to make the observations of the past century insignificant, whether human-induced or not.

 

[Andre]

The insignificance of anthropogenic global warming, yes or no, could be illustrated by projecting the assumed warming of 0.8C since 1850AD on the http://home.wanadoo.nl/bijkerk/alley-3.GIF . It's the red line on the magnification of the last 4000 years.

Curious btw that such historically major publication gets so much reactions in a thread. Also the media are on to it: shouting headlines everywhere. Just check google:

"No More Global Warming" BBC reports

"Global Warming Scare Terminated, Kyoto to be abandoned" The Herald Tribune

"Natural or Human, Global Warming Insignificant anyway", New Science

etc, etc,

Now think about this, what would have been the role of the media in creating the myth of global warming? and what would happen to first one who proves conclusively that the hype is unfounded? He'll be shot and disappear quietly, nobody needs to know.

 

[EdGCM_Project]

Statistics aren't required to forecast global warming

Andre, could you confirm your BBC, Herald Tribune, and New Science quotes with a URL or citation? I can't locate them anywhere.

Also, the key line in the abstract you quoted seems to me to be: "it may be preferable to acknowledge that the concept of statistical significance is meaningless when discussing poorly understood systems." Since the Earth's climate system is complex, it qualifies. However, there are many, many systems (e.g. the human body, economics) that also qualify as complex and yet experts in those fields are able to make substantial progress and useful forecasts. Though not always correct in every detail, fundamental predictions about complex systems prove fantastically useful to society all the time.

Most important, please be aware that forecasts of global warming are not based solely on 20th century trends of temperature. In fact, the trend in the forcings (greenhouse gas increase) is highly significant and an understanding of the basic physics of planetary warming due to the trapping of longwave radiation allows us to make predictions that are based more soundly on physical mechanisms than on statistical methods.

"No More Global Warming" BBC reports
"Global Warming Scare Terminated, Kyoto to be abandoned" The Herald Tribune
"Natural or Human, Global Warming Insignificant anyway", New Science
etc, etc,
Now think about this, what would have been the role of the media in creating the myth of global warming? and what would happen to first one who proves conclusively that the hype is unfounded? He'll be shot and disappear quietly, nobody needs to know.

 

[Andre]

Any idea what cynism is?

It's called: How to ignore really important news

 

[Andre]

please be aware that forecasts of global warming are not based solely on 20th century trends of temperature. In fact, the trend in the forcings (greenhouse gas increase) is highly significant and an understanding of the basic physics of planetary warming due to the trapping of longwave radiation allows us to make predictions that are based more soundly on physical mechanisms than on statistical methods.

Please run that again after having read a few threads here.

https://www.physicsforums.com/forum...p=40&sort=postusername&order=asc&daysprune=-1

We really don't know nothing and your parametrization is based on quicksand.

 

[Mk]

the trapping of longwave radiation allows us to make predictions that are based more soundly on physical mechanisms than on statistical methods.

Of course a theory is nothing, without [statistical] data to back it up completely.

 

[oblong]

The insignificance of anthropogenic global warming, yes or no, could be illustrated by projecting the assumed warming of 0.8C since 1850AD on the http://home.wanadoo.nl/bijkerk/alley-3.GIF . It's the red line on the magnification of the last 4000 years.

Of course applying an 0.8C rise to a graph of global average temperature for the last 20,000 years does show a significant increase.

 

[EdGCM_Project]

Models, Data, Observations

Of course a theory is nothing, without [statistical] data to back it up completely.

If by "[statistical] data" you mean "observations" I agree. But, for global climate we are dealing with a drastically under-observed system that, nevertheless, we as a society need to be able to make predictions about. Numerical simulations, based on physics fundamentals, provide two things that statistical analysis of data alone cannot: 1) they allow us to explore the interplay of mechanisms so we can explore the myriad of feedback processes that occur between cause and effect, 2) even if the system is forced in ways that are outside the realm of the observed database we may still be able to make useful predictions. For example, it was useful to have a few test flights of Boeing 777's prior to moving them into production, but computer simulations allowed them to be "tested" under extreme conditions that wouldn't be reasonable to test empirically (emergency landings, effects of extreme turbulence, etc.). Thus, computer simulations served a "predictive" capacity in the absence of observations. You're correct that no theories are proven in this manner, but pragmatic scientific concerns can be addressed with great success.