Garth Paltridge: Climate’s Uncertainty Principle

Fine summer weather [image credit: BBC]

Plenty of assertions, but we’re still no nearer to knowing ‘what fraction of the observed rise in global surface temperature over the last thirty or so years…is attributable to the human-induced increase in atmospheric carbon dioxide’. It could be anything, including nothing. We don’t even have a CO2 number to work with, as any natural increases are hard to quantify. But in many countries national energy policy ploughs on regardless of the huge uncertainties.

The bottom line of politically correct thought on climate alarm is so full of holes that it brings the overall sanity of mankind into question, argues Garth Paltridge.

That is, we need to put a dollar number to the cost of doing something now, a dollar number to the benefit thus obtained by the future generations, and a number to a thing called “discount for the future”—this last being the rate at which our concern for the welfare of future generations falls away as we look further and further ahead.

Only the first of these numbers can be estimated with any degree of reliability.

Suffice it to say, if the climate-change establishment were to have its way with its proposed conversion of the global usage of energy to a usage based solely on renewable energy, the costs of the conversion would be horrifically large. It is extraordinary that such costs can even be contemplated when the numbers for both the future benefit and the discount for the future are little more than abstract guesses.

Assessment of the future benefit is largely based on two types of numerical modelling. First, there are the vast computer models that attempt to forecast the future change in Earth’s climate when atmospheric carbon dioxide has increased as a consequence of the human activity of burning fossil fuel.

Second, there are the computer-based economic models which attempt to calculate the economic and social impact of the forecasted change of climate. Reduction of that impact (by reducing the human input of carbon dioxide to the atmosphere) is the “benefit” in the cost-benefit calculations.

Taking the climate change calculations first, it should be emphasised that in order to be really useful, the forecast must necessarily be of the future distribution of climate about the world—on the scale of areas as small as individual nations and regions. Calculating only the global average of such things as the future temperature and rainfall is not useful. The economic models need input data relevant to individual nations, not just the world as a whole.

Which is a bit of a problem. The uncertainty associated with climate prediction derives basically from the turbulent nature of the processes going on within the atmosphere and oceans. Such predictability as there is in turbulent fluids is governed by the size (the “scale”) of the boundaries that contain and limit the size to which random turbulent eddies can grow.

Thus reasonably correct forecasts of the average climate of the world might be possible in principle. On the scale of regions (anything much smaller than the scale of the major ocean basins for example) it has yet to be shown that useful long-term climate forecasting is possible even in principle.

Continued here.

Full essay here.