Posts Tagged ‘Climate sensitivity’

Climate models would fit data better if they drastically reduced carbon dioxide “forcings”

August 9, 2015

It is almost the first lesson I was taught when I started doing “research”. Research 101. If the data does not fit the model, you change the model – not the data. The fundamental problem with climate models is that they are not falsifiable. And as long as “climate science” can not, or will not, put forward falsifiable hypotheses, it is not Science. The models all start with assumptions which are approved by the high-priests of the religion. The results are then “forced” to fit with past data and are then used to assert that the initial assumptions are correct. When they are then used for making forecasts they invariably fail. They then try to “adjust” the data (cooling the past) rather than change their religiously-held assumptions.

Five year running mean temperatures predicted by UN IPCC models and observations by weather balloons and satellites. University of Alabama’s John Christy presentation to the House Committee on Natural Resources on May 15, 2015.

Five year running mean temperatures predicted by UN IPCC models and observations by weather balloons and satellites. University of Alabama’s John Christy presentation to the House Committee on Natural Resources on May 15, 2015.

Just the effect of carbon dioxide concentration on incoming and outgoing radiation is small, easy to include and not really an issue. The problem arises because of the assumptions made of the feedback loops and the subsequent “forcing” attributed to carbon dioxide concentration. It is politically incorrect and therefore no climate model is ever allowed to ignore carbon dioxide “forcings”. Even though the “forcings” are largely conjecture. The feedback loops due to changes in carbon dioxide concentration acting through consequent changes in water vapour concentration and cloud cover are not only not known – it is not even known if they are net positive or net negative on temperature. The unknown “forcings” are called “climate sensitivity”, just to make it sound better, but these “climate sensitivities” are little better than fudge factors used by each model. (Even more fudge factors are applied to assert how man-made carbon dioxide emissions affect the carbon dioxide concentration even though the long-term data show that carbon dioxide concentration lags temperature). What I note is that the error between the models and real data is of the same magnitude as ascribed to the effects – with “forcing” – of carbon dioxide concentration in the atmosphere. There is no evidence that the assumed “forcings” are valid. The obvious correction to be made in the model assumptions is that the “climate sensitivity” assumed for carbon dioxide concentration is too high and that any “forcing” effects must be scaled down. But that, of course, is politically incorrect. You cannot get funding for developing a model which does not pay homage to the orthodoxy.

A simple sanity check shows that every single climate model used by the UN’s IPCC would fit real data better if it used a much lower sensitivity to carbon dioxide concentration by using a lower level of assumed forcing.

Another unverifiable doomsday model predicts 4°C rise by 2100

December 31, 2013

What must first be noted is that the lead author, Steve Sherwood,  is from the Climate Change Research Centre, University of New South Wales and is a colleague of Chris Turney – the global warming cheer-leader currently stuck in the Antarctic ice. The paper is largely unfounded speculation – no evidence or measurements in sight –  but speculation alarmist enough for Nature to publish it. The paper – according to the Nature Editor

offers an explanation for the long-standing uncertainty in predictions of global warming derived from climate models. Uncertainties in predicted climate sensitivity — the magnitude of global warming due to an external influence — range from 1.5° C to 5° C for a doubling of atmospheric CO2. It has been assumed that uncertainties in cloud simulations are at the root of the model disparities, and here Steven Sherwood et al. examine the output of 43 climate models and demonstrate that about half of the total uncertainty in climate sensitivity can be traced to the varying treatment of mixing between the lower and middle troposphere — and mostly in the tropics. When constrained by observations, the authors’ modelling suggests that climate sensitivity is likely to exceed 3° C rather than the currently estimated lower limit of 1.5° C, thereby constraining model projections towards more severe future warming.

Clouds are not well understood it seems but they are the answer!

The time-scale for their predictions – till 2100 is sufficiently far away that nothing can be confirmed or denied.

Presumably Sherwood was one of those advising the pilgrims trapped in the Antarctic.

Spread in model climate sensitivity traced to atmospheric convective mixing, Steven C. Sherwood, Sandrine Bony & Jean-Louis Dufresne, Nature 505, 37–42, doi:10.1038/nature12829

Abstract:Equilibrium climate sensitivity refers to the ultimate change in global mean temperature in response to a change in external forcing. Despite decades of research attempting to narrow uncertainties, equilibrium climate sensitivity estimates from climate models still span roughly 1.5 to 5 degrees Celsius for a doubling of atmospheric carbon dioxide concentration, precluding accurate projections of future climate. The spread arises largely from differences in the feedback from low clouds, for reasons not yet understood. Here we show that differences in the simulated strength of convective mixing between the lower and middle tropical troposphere explain about half of the variance in climate sensitivity estimated by 43 climate models. The apparent mechanism is that such mixing dehydrates the low-cloud layer at a rate that increases as the climate warms, and this rate of increase depends on the initial mixing strength, linking the mixing to cloud feedback. The mixing inferred from observations appears to be sufficiently strong to imply a climate sensitivity of more than 3 degrees for a doubling of carbon dioxide. This is significantly higher than the currently accepted lower bound of 1.5 degrees, thereby constraining model projections towards relatively severe future warming.

It all smacks of post-rationalisation.

Garbage In Garbage Out.

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