Can climate models recreate the observed variations in global temperatures?

Question

Which climate model best matches the observed changes in global temperature?

Answer 1

Very good question. A simple answer would be that they can but with limitations.



There are numerous climate models, some quite simple and others that are incredibly complex, by and large there’s not really that much difference in accuracy. The main difference is that the complex models look at more aspects of the climate.



Indeed, the very first climate model was one developed in the 1970’s by the JASON’s and was simply called The Climate Model of the World. It’s predictions have been very accurate with all temperature predictions coming within 0.05°C of real-world values.



When it comes to actually recreating past temperatures, all models are very good at doing this. In producing the model, one of the things that the modellers will do is to produce hindcasts (opposite of forecasts). The models can be tweaked to accurately recreate the historical climate and in doing so, make them better at forecasting.



Even a basic model will factors in many variables including:



• The land↔atmosphere interaction



• The soil↔biosphere interaction



• The atmosphere↔biosphere interaction



• The ice↔ocean interaction



• The atmpsphere↔ice interaction



• Cryospherics: Glaciers, ice sheets, ice shelves, sea-ice, snow, permafrost, frozen ground etc



• Land surfaces: Vegetation, geomorphology, ecosystems, land use, land use change, albedo, volcanoes



• Oceanics: Biogeochemistry, thermohaline and other circulations, sea-levels



• Hydrology: Evapouration, transpiration, precipitation, cloud cover



• Weather: Wind stresses, wind dynamics, thermodynamics



• Oscillations in the oceans and atmosphere. Very long term models will take planetary oscillations into account.



• Radiation: Terrestrial and solar, changes to both



• Boundary transitions



• Changes in solar activity



• Changes in human activity



All the models will produce forecasts that include basics such as temperature and atmospheric changes, most models will also focus on some specific areas of the climate.



The overall accuracy varies greatly, some models have been way off the mark, others have been spot on. No model has been completely wrong, similarly none of them have been entirely accurate either. The early simple models perhaps had an accuracy of 70%, today’s complex models have about the same degree of accuracy. I wouldn’t like to single any one out as being the best or the worst as they all have their uses.



More info…



Climate Models: An Assessment of Strengths and Limitations

http://www.clivar.org/organization/wgcm/references/sap3-climate-models.pdf



Climate Models and Their Evaluation

http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter8.pdf



The JASON’s climate model of the world (the first real climate model)

http://www.nap.edu/catalog.php?record_id=12181



IPCC Model Outputs

http://www.ipcc-data.org/ar4/gcm_data.html

Answer 2

So far they have failed miserably. James Hansen is the head of the NASA unit making predictions about Global Warming. Have a look at his prediction below:



James Hansen Climate Prediction

http://c3headlines.typepad.com/.a/6a010536b58035970c015392efff32970b-pi



Do you see the GREEN line at the top? That was Hansen's prediction for "business as usual" or -- "no CO2 reductions," and of course CO2 has NOT been reduced. According to the GREEN line we should be seeing about 1.2C above 'normal' by now ---- BUT WHAT ARE WE ACTUALLY SEEING?



THAT WOULD BE THE RED LINE, yes, that's right, the line at the very bottom, showing only about 0.3C of warming is the ACTUAL temperature at the time this graph was produced.



Hansen gave himself three scenarios in order to give himself a wide range in which he could say he was correct. But he STILL GOT IT WRONG !!



Climate models have proven themselves worthless. That's because they are based on the nonsense that CO2 drives temperature --- which it does NOT.



You should watch these and see some of the world's top climate scientists explain it in detail.





The Great Global Warming Swindle

http://www.youtube.com/watch?v=Ov0WwtPcALE



Global Warming Doomsday Called Off

http://video.google.com/videoplay?docid=-3309910462407994295#



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Answer 3

Sure they can. The best fit to actual observations is an average of several climate models, or even the average of one model run many times (see link).

Answer 4

Yes, but this is of minimal relevance to the basic science.



The models are tools that help researchers to discover the science, but the science itself does not depend on them. What human-caused increases in greenhouse gases do to the global climate, and what global climate change does to the global environment and global economy, do not depend on how exact or inexact the models are in predicting either the short term variations or the long term pattern of gas concentrations, average temperature increases, feedbacks, natural cycles, etc.



By analogy, no economic model has ever been able to consistently predict the future trend of the stock markets, but this doesn't mean that if the government taxes corporate profits and equities trading, and increases such taxes steadily year after year, that there won't be a predictable and negative effect on the long term trend of stock prices.



Continually increasing taxes on corporate equities (or you could substitute collusion amongst traders to steadily increase their margins) are analogous to the increasing tax or economic burden imposed on the future global economy by its long term dependency on climate-disrupting fossil fuels.



By the way, since the science-flunking climate change deniers have since come out in force on this pasge, here is that basic science, as concluded by TOP REAL scientists, not the charlatans and pseudo-scientists which the deniers endless copy and paste:



U.S. National Academy of Sciences, 2010:

http://books.nap.edu/openbook.php?record_id=12782&page=1

“Climate change is occurring, is caused largely by human activities, and poses significant risks for a broad range of human and natural systems.”

http://nationalacademies.org/morenews/20100716.html

“Choices made now about carbon dioxide emissions reductions will affect climate change impacts experienced not just over the next few decades but also in coming centuries and millennia…Because CO2 in the atmosphere is long lived, it can effectively lock the Earth and future generations into a range of impacts, some of which could become very severe.”

http://www.physics.fsu.edu/awards/NAS/

“The Academy membership is composed of approximately 2,100 members and 380 foreign associates, of whom nearly 200 have won Nobel Prizes. Members and foreign associates of the Academy are elected in recognition of their distinguished and continuing achievements in original research; election to the Academy is considered one of the highest honors that can be accorded a scientist or engineer.”



For further details see:

http://www.newscientist.com/topic/climate-change

http://www.aps.org/publications/apsnews/200602/backpage.cfm

http://www.aip.org/history/climate/timeline.htm

http://www.skeptic.com/eskeptic/12-02-08/#feature

http://www.newsweek.com/2007/08/13/the-truth-about-denial.htmlhttp://opinionator.blogs.nytimes.com/2011/07/12/on-experts-and-global-warming/

http://en.wikipedia.org/wiki/Global_warming

Answer 5

No.



That is why so many of us rejct them. Only "adjusted" models can meet the "adjusted" data sets provided to them.



They do NOT publicize nor do they release how and/or why models and datasets are "adjusted".