Radiative forcing is a fundamental quantity for understanding both anthropogenic and natural changes in climate. It measures the extent to which human activities [such as the emission of carbon dioxide (CO2), see the image] and natural events (such as volcanic eruptions) perturb the flow of energy into and out of the climate system. This perturbation initiates all other changes of the climate in response to external forcings. Inconsistencies in the calculation of radiative forcing by CO2 introduce uncertainties in model projections of climate change, a problem that has persisted for more than two decades. The explicit calculation of radiative forcing and a careful vetting of radiative transfer parameterizations provide a straightforward means to substantially reduce these uncertainties and improve the projections.

Read more:
http://science.sciencemag.org/content/361/6400/326

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Reading the full article, one starts to ponder how the devil one goes about this. The problem of prediction via this kind of modelling still persists despite more and more data. I am in favour of simplicity and base my own flimsy models on empirical estimates extracted from past data (including Vostok). 

Because of politics, scientists need to produce a complicated formula to constraint the possibility of global warming in terms to what everyone can agree upon. The problem of “radiative forcing” has been raised by the denialist lobby with a vengeance. So the Paris agreement was set at less than 2 degrees Celsius with “reduction of emission of CO2 to match”, while considering the radiative forcing. In my book, this is politics, not science. 

As the full article points out: This limit should be established by a multimodel ensemble, but the corresponding range of allowable CO2 concentrations is unnecessary large because the ensemble does not consistently incorporate known and established physics that relate rising CO2 concentrations to radiative forcing...


Houston, we have a problem. 

Most of the models of global warming have not been implemented with accurate calculations of radiative forcing, because "it does not really matter" says Gus...

So what is radiative forcing?

Radiative forcing or climate forcing is the difference between insolation (sunlight) absorbed by the Earth and energy radiated back to space.

Simple, yet very complicated, because as the surface of the earth warms up under global warming condition, there is a possibility that more energy is radiated back to space. At which point is this going to balance out, and prevent the surface of the planet to warm up more? 

This is a bit like cooking with or without a lid on top of the saucepan.

It’s going to take longer and use more energy to achieve boiling point without a lid. At this stage, planet earth has a variety of lids that are at iffy-stiffy stage. Concentrations of radiatively active gases, commonly known as greenhouse gases, and aerosols can alter the forcing very quickly, and at which altitude are we going to see some influences that will interfere with our calculations. So new models are studying data from about 12 kilometres above the surface while others will study the forcing from the edge of the atmosphere. By knowing this energy lost and the energy gained we should be able to gauge the difference — i.e. global warming. 

Apparently, there has not been any progress for the last 25 years on assessing the energy lost (radiative forcing), and the climate sensitivity (global warming) is thus estimated as 1.5 to 4 degrees Celsius at the moment. 

This is why I do not try this caper. I have too little computing power in my head. But I can do better estimates. 

How much is radiative forcing increasing when the global temperature changes from 7 degrees Celsius (Ice ages) and 15 degrees Celsius (warmer climes)? This is a relative minor change of the earth surface temperature, yet important enough in its resulting status. But is the radiative forcing much different? My personal guess would be not much considering the actual temperature of space which is about 3 degrees K — cosmic background temperature, which is minus 455 degrees Fahrenheit or minus 270.45 Celsius.

This means we would have to consider a difference of running potential between 270 + 7 (cool) and 270 + 15 in normal warm condition which is 285 divided by 277 (cool) or around 0.102 per cent fluctuation. Is the forcing going to change much with an extra 4 degrees on the surface? the difference of running potential is 0.104. Not much difference. 

Even with a twelve degrees extra due to global warming, the difference is 0.1072. So when estimated such, the radiative forcing is going to be far less influential than the actual warming. And with the measured observations of the forcing being a bit all over the place (we know that atoms in the thermosphere oscillate between 500 and 2000 degrees Celsius), it would be a good idea to discount it for the plebs like us (and the politicians)— and keep this small interference in global warming between Chardonnay sipping specialists. 

No matter what, with an extra 110 ppm of CO2 above the natural setting of warm climate of 300 ppm, at this level we can estimate a MAJOR warming problem. 

At this stage we thus have to go back to the drawing board and find a reference point already established: with no CO2 in the atmosphere, the temperature of the surface of the earth would be minus 35 degrees Celsius.

This is our relative bottom limit. So with 180 ppm above this 0 level of CO2 we reach the glorious temperature (cool) of 42 degrees Celsius (35 + 7). With 300 ppm of CO2 we know we reach the temperature (warm) of 50 degrees above this (35 + 15). Extrapolate the next level of temperature with an extra 100+ anthropogenic ppm (400+) and the temperature is between 56 and 58 degrees above the minimum with no CO2 in the atmosphere. That is to say, with the amount of CO2 we ALREADY have added in the atmosphere, we are on the way to a BASIC temperature INCREASE of 6 to 8 degrees above our present average of 15 degrees (50 degrees Celsius above our atmosphere with zero CO2 [minus 35 degrees Celsius]). The radiative forcing would have a minimalist effect on these changes, as the radiative forcing influence has to be established from the minimum cosmic temperature.

There are many feedback mechanisms that are retarding the surface temperature increase, as well as other feedback mechanism that are pushing it up. Here we have to consider the melting of the ice sheets and glaciers all over the world that have a major impact in RETARDING the warming process. Important other factors which will increase the temperature are METHANE and NOx. 

Now the increase of radiative forcing is minimal compared to the POTENTIAL INCREASE of temperature. 

With the extra CO2 we’re going to let ourselves indulge in the next few years, my calculations tells me that the temperature will plateau at about 12 degrees Celsius on top of present temperatures, by around 2250. 


No kidding. And I could be wrong!


Gus Leonisky 

Your local former mathematician/accountant

Read also:
http://www.yourdemocracy.net.au/drupal/node/33287


Update: by 2032, the EXTRA anthropogenic and from disturbance to photosynthesis CO2 emissions are likely to reach 500 ppm. At this stage the potential warming will be around 12 degrees Celsius. Mitigating/retarding factors such as melting of ice-sheets will delay the onslaught, masking the true potential of increase warming yet the atmospheric perturbations could be catastrophic. See: wearing a beige cardigan on a hot day at the beach because mum said so...

 

By then, the rise of the oceans level will become highly noticeable to reach at least a metre on present levels by 2100.