I spent a large part of my early career in mathematical modelling (of combustion systems and of heat flow) and have a very clear idea of what models can do and what they can’t. Models after all are used primarily to simplify complex systems which are otherwise intractable. They are – always – severely limited by the assumptions and simplifying approximations that have to be introduced. Models are a powerful tool for investigation but are only as good as their most inaccurate assumption. But they are a tool primarily for investigation — and can be dangerous when used for decision making based on their imperfect predictions. The spectacular failures of mathematical models of the global economy are a case in point. It is worth noting that in spite of the great strides made in weather forecasting for example – much of which is empirical – the simple statement that “tomorrows weather will be like today’s” is as correct – statistically – as the most complex model running on some super-computer somewhere.
It has therefore always amazed me that so-called “scientists” would be so certain about their approximate models of climate systems – which are perhaps as complex, chaotic and “unknown” systems as any one could study. It has been a boon for politicians looking for new ways of raising revenue. It has been exploited by the alarmists since the alarmist predictions cannot be tested. The wide spread of results from climate models is rarely mentioned.
When reality does not match model forecasts it is time to back off and rethink the models and hopefully they will be better next time. And it is time to back track from all the political decisions made on the basis of patently incomplete and inaccurate models.
The simple reality about climate is that rather than being a “settled science”
- we don’t know the impact of solar effects on climate
- we don’t know the impact of clouds or even if they are net “warmers” or net “coolers”
- we don’t know how much of the earth’s radiative energy balance is dependent upon carbon dioxide
- we don’t know how much carbon dioxide is absorbed by the oceans and living things
- we don’t know the impact of aerosols and particles in the atmosphere
- we don’t know the role of the oceans in transporting heat around the globe
- we don’t know how much heat is stored in the oceans and how it varies
- we don’t know the impact of solar effects on cloud formation
- we don’t know what triggers ice ages, and
- we don’t know what we don’t know.
This from Dr. Roy Spencer and the ridiculously wide spread of the model results and the obvious deviation of reality from model results are particularly striking:
Since the slowdown in surface warming over the last 15 years has been a popular topic recently, I thought I would show results for the lower tropospheric temperature (LT) compared to climate models calculated over the same atmospheric layers the satellites sense.
Courtesy of John Christy, and based upon data from the KNMI Climate Explorer, below is a comparison of 44 climate models versus the UAH and RSS satellite observations for global lower tropospheric temperature variations, for the period 1979-2012 from the satellites, and for 1975 – 2025 for the models:
Clearly, there is increasing divergence over the years between the satellite observations (UAH, RSS) and the models. The reasons for the disagreement are not obvious, since there are at least a few possibilities:
The dark line in the above plot is the 44-model average, and it approximately represents what the IPCC uses for its official best estimate of projected warming. Obviously, there is a substantial disconnect between the models and observations for this statistic.
I find it disingenuous for those who claim that, because not ALL of individual the models disagree with the observations, the models are somehow vindicated. What those pundits fail to mention is that the few models which support weaker warming through 2012 are usually those with lower climate sensitivity.
So, if you are going to claim that the observations support some of the models, and least be honest and admit they support the models that are NOT consistent with the IPCC best estimates of warming.