Are 400 ppm of CO2 the border to beginning the Armageddon, or not?

At last we arrived at 400 ppm of CO2 in the atmosphere.  Two decades of conferences, commitments and challenges don’t stop the growth of CO2 atmospheric concentration. But we aren’t listening celestial trumpets or seeing angels armed with fire-swords down from heaven. It’s true, the predicted Apocalypse doesn’t start yet, but the barrier of two times the concentration of CO2 of pre-industrial age is significant not to be a round number bur it had never exceeded in the last 600,000 years. However importance is that in first we are entering in ‘terra incognita’ with respect to fossil records, and second ours mathematic climatic models are out too of confidence interval; and now anything unforeseen or expected can happen.

What does it mean Terra Incognita? As I explained in: Really are temperatures stopping its rice, climate models are a set of nonlinear differential equations and as such are very conditioned to the boundary conditions; this determines the calculation in long term so that the evolution of the real current weather change forecast. Moreover these equations have coefficients and parameters which we have been found empirically; and the modern climatology only has data of the last 200 years, and really precise the last 50; therefore the coefficients are tabulated in this short period of climatic conditions, and no one really knows if these are valid for a higher quantity of CO2 for example. So our forecasts will now have a greater degree of uncertainty, and they are more subject to the assumptions of the model.
This doesn’t mean that climatology forecast will be bad, only it means that temporal projection suffers more deviation. Overall climate will change for the simple reason that global conditions have changed too, but to lose the validity of the parameters we must made assumptions that depend on each modeling, and so some modeling show a warmer climate, others drier, another colder... but this is the destination in the long term that will be clarified as they improve the parameters; still the uncertainty arising from the imposition of chaos can’t ever eliminate. But when I refer to terra incognita is in the sense that the evolution in the short and medium term, with high degree of precision today, it will become less precise, even it’s affecting meteorological models, which will difficult work of warning the population that it has saved so many lives until today.
In this sense it’s here where they have begun to sound the alarm* for two reasons: first as I said before, CO2 records have never surpassed this level during 600,000 years of complete records, and therefore we don’t know exactly how the climate behaves in this conditions having to go back to the Pliocene to find these ranges; and the second about an estimate made by the IPCC which shows what would happen with double CO2 in the atmosphere, this being a little controversy because it us a parameter ‘Climate Sensitivity’. The Guardian article "What you need to know about climate sensitivity," explains a bit although it is not quite that, then I do a little explanation.
Regarding the Pliocene, this is a warm period within a current ice age, Cenozoic, just before the arrival of Homo genus** 1.8 million ago, and began 5 million years. With these dates accurate radioactive date stamps, as the C-14, will not work because they have gone (this is the reason that I call them complete records to distinguish them of indirect methods, they are not necessarily bad, but less accurate, it is own nomenclature), so we have to be guided by indirect methods to locate in time the fossil record. In the case evolve into the Pliocene we find a much warmer climate and a drastic reduction of the continental ice, I must say that Antarctica wouldn’t lose its ice so even sea level rise, this would not exceed few tens meters, fatal to the coastal lowlands and islands, but not the 200 meters or more that produces the disappearance of the Antarctic ice. But that does not mean the end of humanity necessarily, but as I said many times warmer weather generates a displacement of both animal and plant species, with consequent chaos in agriculture; this will not be the end of humanity but a very traumatic goal for it.
The IPCC forecast is another matter. Nonlinear expressions with more than three variables, and climate has many more, suffering in the forecast when we will propagate in time. So we chose a linear character expression: if we look at graphic up write, we can see that temperatures evolve lineal and concentration CO2 as exponential so we can deduce that the temperature is a function of the logarithm of the concentration (1); we don’t know what function is but we can develop in potential series around a known point with temperature and concentration (XCO2) knowing (2), where lambda is a parameter that we call Climate Sensitivity.

To get lambda we would just use another known point, but this is too simple expression for lambda must be significant. In this regard we must find a better expression, and this we will achieve, not from the concentration of CO2, but rather from its consequence what is the change in energy balance that produces, this is called Radiative Forcing. From expression (3) we can get a better value of lambda because we can find dependence of it (4) with real values on the planet.

Lambda, as shows (4), only depends on the Heat Capacity of the Planet Cortex (Cp) *** (continent, oceans and atmosphere) and a constant (tau). The Cp is the amount of energy stored per degree of body temperature increases. If we put something on a stove to heat up, the time it takes to heat up depends on the value of this constant, always the fire burn constant, which we can see every day, water is heating more slowly than oil. To find this quantity we need to isolate the body in question apply a constant energy and observed temperature change, something totally impossible to make to terrestrial crust. Luckily, most of whom you are the ocean energy (85%), and we know Cp. of water. After we only have associated the increase of see water energy from Global Surface Mean Temperature (GSMT) getting enough real value of earth's crust Cp. The tau is something a little more esoteric, in fact it is a time (and it must be because the exponential is dimensionless) represents the time it takes to feel the effect from the forcing. The value of this delay we can get from occasional increases of CO2, such as volcanic eruptions, and find the average time between the increase and the change in GSMT.
Despite they are clearly defined magnitudes, to get the value it isn’t so simple. As for the tau example volcanoes simultaneously they fill the air with dust that reduces radiation, and even increase the energy absorption capacity of the crust to get less energy not seen significant increases;  and other types of forcing are other variables that attenuate or magnify as explained in Feedback. This set of difficulties force to make corrections which have to take assumptions which have more or less weight depending on the author, so we can find values that range from 11 years to 5 years errors of +-3 or 1 years. But it isn’t easy to get Cp, even we restrict it to the ocean energy to know it isn’t easy. Not have full details of the temperatures of the ocean water and less its global evolutions, therefore this empirical value has also very dear, although there is enough consensus value but very subject to change. In short it is difficult to obtain this value and adds uncertainty to the forecast, which the skeptics are profiting to take advantage.

Really did we pass the border that brings disaster? At first glance it would seem that no, we have the concentration and we still haven’t the temperature, therefore appears that the forecast has failed. However we aren’t so far from the IPCC forecasts regarding temperatures; to have Pliocene order concentration to CO2 and to be far from its temperature doesn’t mean anything, Pliocene lasted 4 million years and current CO2 concentration only two weeks ago, on the other hand I said before that the accuracy isn’t great and we know the average values of a long period where temperatures and CO2 fluctuated sure. But the thing that covered value more in border is twice the distance from the base value of CO2, and therefore the linear approximation is no longer valid having to add additional terms, which need more sensitivity coefficients with the problem to find their values.
In definite when I say ‘terra incognita’ it means that there is only a sure thing: the weather will not be like before. A change of climate that changes coastlines, current distribution and production of crops, and the structure of species on earth which will be clearly affecting the microbial world and repercussion of these to the health (reasons exposed in the perfect storm). And amazingly this news has gone unnoticed in the mass-media, it has come out as press releases or directly in tabloid specializing in climate (often with exaggerated claims). Meanwhile oil companies and economic lobbies are indecent amounts for giving voice to climate-skeptic, consumer groups are demanding the right to unlimited energy and governments forget their commitments.

 

* Alarms have sounded to burn but it seems that our leaders are deaf
** Technically are right when they say which are historically the largest concentrations
*** p means at pressure constant, the pressure does not change in global