1. Computer models that forecast the weather
Gareth Renowden at Hot Topic has finally lost whatever finger-nail grip he ever had on climate science.
He now claims (incredibly) that national temperature records “play no part in planning” since forecasts come from computer models, not carefully-kept historical records. It’s sad, really, that NIWA totally disagrees with him. And we shall prove it.
Our good friend Chris de Freitas wrote an excellent article for the NBR on 14 November reporting on the paper by him and his co-authors—a reanalysis of the NZ temperature record (NZTR), published last month in Environmental Modeling & Assessment. Renowden first quotes de Freitas:
National temperature trends are widely used for a large number of societal design and planning purposes and it is important that they should be as reliable as modern methods allow.
This is transparent nonsense. Historical temperature trends are interesting, but they play no useful part in future planning. To plan in the face of rapid climate change, we need good regional projections for temperature changes, sea level rise and increases in weather extremes. Those will come from climate models, not temperature records.
We do agree that New Zealand’s national and regional temperature projections will continue to come from NIWA’s uber-expensive super computer. But you have to feed it something. So the 64,000-dollar question is: Where does the mathematical model come from and what data goes into it?
In simple terms: what on earth does it start with? The answer is, of course, it starts with reality: with now.
Historical observations are used to develop regression equations that relate local climate fluctuations to changes at the larger scale. These historical observations are then replaced by the model changes in the regression equations to produce the fine-scale projections. [emphasis added]
So, historical observations of the New Zealand climate (for example, the 7SS temperatures) are the starting point for downscaling the global models. This is hardly surprising, as every projected trend is by definition an extension of past trends. You have to know accurately where you are to start with.
NIWA doesn’t say whether it uses the 7SS raw data or the homogenised series set out in Mullan10, but I’m betting it’s the latter. That means the downscaling project is fed with a temperature trend that’s 300% too high.
It has proved impossible to verify climate models. Their projections have a very poor record world-wide and virtually all the CMIP3 models have consistently over-stated global mean surface temperatures for the past 20 years. However, an effort is invariably made to improve performance by calibrating and tweaking the model until it is able to “hindcast” the observed temperature record for previous decades.
David Wratt and Brett Mullan say on the NIWA website:
If we are to have confidence in future projections of climate models, it is vital to first test them against observed climate to see whether they realistically simulate different climatic conditions which were observed during the earth’s past. [emphasis added]
So the downscaled NIWA model has been calibrated by reference to Mullan’s version of the 7SS, using exaggerated adjustments. If it is managing to hindcast the national temperature trend as warming at the rate of 0.91°C/century, its untestable future projections are completely useless.
An important example of misleading projections from the NIWA model is that of mean sea level rise (MSLR). We know from tide gauges that there has been no acceleration of MSLR around New Zealand during the past century. The NIWA model should therefore pick up the fact that the MSLR has not been compatible with the temperature data it has been fed from Mullan’s 7SS. But it doesn’t, because it uses a calculated history of global SLR drawn from satellite data, and ignores the actual painstaking readings that New Zealand scientists have recorded for decades, in some of the longest records in the Southern Hemisphere.
So, Gareth, what do you have to say now about the “transparent nonsense” you alleged of Chris de Freitas? What he said is a perfectly accurate reflection of what NIWA does. What you said is demonstrably wrong—you can check the references for yourself. I think the least you can do is to apologise.
Wratt and Mullan also say on the web site:
Confidence in the ability of climate models to estimate future climate changes comes from the fact that they are based on accepted physical laws such as conservation of mass, energy and momentum, as well as a wealth of observations for their more empirically-based components such as cloud reflectivities or infrared absorptive properties of greenhouse gases. [emphasis added]
Errors in any of these components render the computer model output useless and should be corrected as soon as possible.
Imagine that overseas scientists reported that NIWA was using an incorrectly stated law of physics: say, an incorrect constant value, or a wrongly formed equation. NIWA scientists would move so quickly to fix a mistake like that that they would be mere blurs in the corridors, their speed immense. They have put in an enormous amount of work to build up credibility with colleagues around the world and would spare no effort to correct such critical errors.
Well, we don’t need to imagine anything, because this is reality: what has actually happened is that local scientists have reported that NIWA has been using an incorrectly stated national temperature record. Why are they not running to fix it? Do they disagree with the laws of physics?
We haven’t seen a reply yet to our rebuttals of your debating points, Gareth.