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globalwarming awareness2007
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Autumnmae a posté une photo :
So if you think there is no global warming or greenhouse effect look at this. It is the middle of January and it was 75 damn degrees at 430 in the afternoon. I know you midwest and east coast folks hate us bad out here. Its a shame I've never owned a heavy coat all my life and I've only been in the snow once. *Sigh*
As the climatic situation to come will be probably unknown since the man started his terrestrial existence, the only tools we currently have to try to know what can occur in the future are climatic models.
A climatic model is not anything else perhaps (the climatologists will find that it is already not so badly!) that a very complex software, of which the goal is to as accurately reproduce as possible the behavior of the terrestrial climate. It is thus about a large program for computer, built in the following way:
one ?models?, i.e. that one represents, by mathematical equations, the principal laws who govern our atmosphere,
one transforms these equations into lines of data-processing code,
as one cannot describe what occurs absolutely everywhere (that would require to treat an infinite number of points, and no computer likes much the infinite one), one makes a grid: one covers our planet with an imaginary net of which the mesh (as for a fishing net, the mesh is the distance which separates two wire) measurement about a few hundred km on side (depends on the models),
Example of grid above Europe for the English model of Hadley Centers. One sees clearly, for example, whom France counts only for 4 meshs (it is the order of magnitude in all the total models; certain models known as regional use smaller meshs - about 50 km - above a particular area but then the meshs for the rest of the world can measure up to 1000 km on side). One includes/understands better than the reliable regional forecasts do not form part of the schedule of conditions of these models (to establish total forecasts one is already crowned task!).
as it is acted in fact of a system in 3 dimensions, the world is not cut out in small squares but rather out of shoe boxes, with a few tens of levels of ?boxes? along the vertical,
within each ?shoe box? one defines starting conditions (corresponds to firm ground or water, occupied or not by a cloud, etc)
Overall diagram of a particular model. Headings (in English, alas!) indicate the elements and interactions taken into account in the model. Source: Hadley Centers.
at each ?node? of this grid in three dimensions (i.e. at the tops of each shoe box), or within each box (that depends on the parameter considered), one fixes the starting conditions by indicating the initial values of the various parameters with which the computer will work: temperature, pressure, moisture, salinity for sea water, cloud cover, wind?,
then one makes ?turn the model?, i.e. that the computer calculates, on the basis of of the equations and the values intiales, how evolve/move the things with each ?node? of the net with intervals of regular times (according to the data-processing power which one lays out, they will be every month or every half-hour!).
One of the advantages of these models is that they can easily take into account a disturbance which evolves/moves in the course of time, for example the increase in the content gas for purpose of greenhouse awareness2007: it is enough to add an equation in the list.
Modeling is a discipline which does not go back to yesterday: the first models date from the Sixties (the first atmospheric model goes back even to 1950, and was tested on the first existing computer, the ENIAC). What allowed a fast rise of the discipline is more the increase of the data-processing power available than the improvement of the knowledge of the operation of the atmosphere, operation which was already rather well known there are a few tens of years (with as consequence that first ?alarms? on the climatic globalwarming date from the end of 1960).
For example, the computing time to simulate one month of evolution was divided by more than 100 between 1980 and our days!
The more the data-processing power increases, and the more one can use meshs of small size. The more one works over short periods, and the more one can also decrease the mesh (what increases the precision of the forecasts): the meteorologists, who are not interested in the climate that there will be in a few centuries, but with that which ago tomorrow or in 3 days, work on models rather close to those which the climatologists use, but with meshs of a few kilometers only.
A small glossary
According to the way in which they are built and what it take into account, the models are indicated with different initials. Here are some:
GCM means ?Total Model Circulation?, and thus in Model French ?of Total Circulation?. It is about a total model, with broad meshs, to give tendencies of long term on broad zones.
AGCM means ?Atmospheric Global Model Circulation?. It is about a particular category of GCM, which take into account only the atmosphere. That gives valid predictions only as long as the other components (grounds, oceans, ices) do not move, and in practice they are the models used for the forecasts weather.
AOGCM means ?Atmospheric Oceanic Global Model Circulation?. It is about another category of GCM, which take into account the atmosphere and the ocean. One sometimes also sees ?Atmospheric Oceanic Global Coupled Model?, bus in these models not only the ocean is taken into account, but also the interactions between the ocean and the atmosphere. These are the models which are used in climatology.
It happens finally that the letter R intercalates some share in the place of G: they are then regional models.
How much models?
There is currently about fifteen models all over the world, on which approximately 2.000 scientists work. However the total number of scientists of different disciplines which concourrent with the construction or the food of the models is quite higher, at least of a factor 10: ?to know what to put? in these models it is necessary to call upon physicists, chemists, biologists, geologists, oceanographers, aerologists, glaciologists, energeticians, demographers?
The laws of physics remain the same ones of course everywhere and all the time, but these models are nevertheless rather different from/to each other: the ones take into account the effects of the clouds like this, the others like that, the ones take into account certain phenomena of the biosphere (the biosphere is the whole of the alive beings), the others not, etc
In France, one of the poles of modeling and study of the climate is the Institute Pierre Simon Laplace (IPSL), gathering:
the Dynamic Laboratory of Meteorology of CNRS (unit common to the Teacher training school, the Polytechnic School, and the University of Paris VI - Jussieu)
the Laboratory of Sciences of the Climate and the Environment (mixed unit ECA - CNRS).
the Dynamic Laboratory of Oceanography and Climatology (mixed unit IRD - CNRS - Jussieu).
service of Aéronomie (mixed unit CNRS - Jussieu - University of Versailles-Saint Quentin).
the Terrestrial Center of study of the Environments and Planet gears (mixed unit CNRS - Jussieu - University of Versailles-Saint Quentin).
the Laboratory of Physics and Chemistry Navy
What do they take in account?
All the models do not take the same thing in account. Here principal the items taken into account. Caution! Taken into account does not want to say that all is known on the point considered, but simply that ?one speaks about it? in the model:
energy exchanges, in particular in the form of electromagnetic radiation, between the Earth, the ocean, atmosphere and space (all models).
radiative transfers in the atmosphere, i.e. the way in which the solar radiation and that emitted by the Earth cross the atmosphere or are absorbed by various gases for purpose of greenhouse awareness2007 contained in the latter,
As one saw, it does not have only one there but several gases for purpose of greenhouse awareness2007. These gases are not taken into account in an independent way in the models: one starts by making the ?amount? of various producedes gas, by balancing them by their respective capacities of globalwarming, and it is this ?amount? which one uses to represent the emissions of all gases for purpose of greenhouse awareness2007.
This precision is important, because it prevents from easily studying by the results of modeling the effects of a beginning of globalwarming on the ?natural? gas emissions for purpose of greenhouse awareness2007 taken one by one. It is in particular the case for the methane, of which the speed of elimination in the atmosphere depends significantly on its concentration.
air circulation in the atmosphere (all models), and thus transport of water which is associated there,
oceanic circulation (all models), and interactions between the ocean and the atmosphere (most recent),
the clouds (most recent), but a correct modeling of the clouds remains one of the points where the margin of progression is very important,
the exchanges of carbon enters the atmosphere and the planet (all models, but with different degrees of sophistication), and recently certain feedbacks of the globalwarming on the gas emissions for purpose of greenhouse awareness2007 (not all, and with different degrees of sophistications).
Which are their weaknesses?
The three great sources of uncertainty of the models are as follows:
First of all our atmospheric system is not entirely foreseeable. It is well for that which it happens that the weather - which works with the same models - is mistaken, even if, statistically, it is right often (but one especially intends to speak about the times where it is mistaken, which induces an effect of deformation: only the tree is not needed masks the forest!),
Then there are inevitable simplifications when a model is built. It is however legitimate and current to proceed of the kind: the simple fact that one made a simplification is not necessarily a source of error. For example, the plan of the architect does not reproduce all the details of the future building but only the ?most important things?: for as much, will one have a bad idea of the facility with which one will circulate in the building?
they represent always only part of the system (but the scientists think that it is the principal one). Among the elements which must be better taken into account, one can quote:
clouds (because they are objects of small size relative to the size of the mesh, therefore that one is thus obliged to treat in an approximate way),
well and sources of oceanic and continental carbon, and in particular influence of the biosphere,
the continental evaporation, which also utilizes of the processes of small scale (i.e. of ?small size? compared to the size of the mesh),
major oceanic circulation (that it is difficult to measure, therefore for which it is difficult to compare what says the model with reality),
the cycle of methane (the gas of ?rotting?), and of the nitrogen protoxide,
the taking into account of the increase in tropospheric ozone (that which is close to the ground),
the role of the organic or mineral aerosols (dust).
But it would not have to be deduced owing to the fact that there remain zones of shades which one can be unaware of the results, which would be to throw the baby with the water of the bath! Moreover, these tools are in perpetual evolution, and thus in perpetual improvement.
Evolution of the degree of complexity of the models since 1970. Source GIEC, 2001 (technical summary WG1)
First conclusions of the models
An essential point is that, even if they are built in a different way, even if the quantified results to which they arrive are not rigorously identical, all these models arrive at conclusions of comparable nature: the man modifies the climate in the direction of a total globalwarming of planet. Moreover these models also state that the human influence will be increasingly strong if the gas emissions for purpose of greenhouse awareness2007 continue like now.
The average temperature of planet will increase (cf below). The fork of the evaluations goes from 1,5 to 6 °C at the one century horizon.
On the graph above one represented, at a rate of a curve per model, the increase in average temperature of the air on the level of the ground (what one calls ?the average temperature of the Earth?) according to the years (the 0 corresponds to today). The vertical axis is graduated in degrees.
All the models were fed with the same assumption: a CO2 concentration which increases by 1% per annum (what is about the rate/rhythm of evolution today). Source PCMDI/IPSL
The exchanges of water between surface and the atmosphere will increase (cf diagram below). That can be explained rather simply (even without model!) : an air overall hotter can contain more steam, and thus evaporation will increase. As the steam does not accumulate in the atmopshère, all that goes up must go down again, and thus an increased evaporation will generate overall more precipitations (and remainder for the ice ages, during which the climate is colder, it makes much drier). That will mean that it will more often rain, or?.more extremely (with an increase in the risk of innondations in this last case)
The curves above (a curve by model) give the evolution of annual average precipitations compared to the current situation (0 of the ordinates). All the models leave the same assumption of a CO2 concentration which increases by 1% per annum. The vertical axis is graduated in millimetres of water per day.
When a curve crosses value 0,05, for example, that means that at this time there average precipitations on the surface of the sphere increase by 0,05 mm water per day, either a little more than 18 mm of water per annum, or still 3,5% of current precipitations (520 mm of water per annum on average).
However this surplus of precipitations would not be distributed in an equal way everywhere: the models envisage great disparities according to the lattitude.
The curves above (a curve by model) give the distribution of the surplus (or the deficit) of precipitations according to the latitude to the moment or the concentration of CO2 in the atmosphere will have doubled (in 60 to 80 years if ?nothing changes?). The vertical axis is graduated in mm of water per day, and thus gives the difference of the average day labourer of precipitations (for the whole ground) between the future situation of simulation and today.
One sees for example that with the Northern latitude 60° (North of Scotland, South of Norway, where it already does not rain badly, it would rain even more (70 mm of water per annum in on average) whereas towards 30°N (California, the Sahara, Mongolia, in short of the little sprinkled places) it would rain as much or rather less, and that towards 30 °S (South Africa, Australia, Argentina) it would rain rather a little less. Source PCMDI/IPSL
Finally there will be a globalwarming more pronounced:
the night (in opposition to the day),
the winter (in opposition to the summer, which is not without consequence for the vegetation, to see further),
with the poles (in opposition to the average latitudes),
The curves above (a curve by model) give the increase in temperature according to the latitude to the moment or the concentration of CO2 in the atmosphere will have doubled (in 60 to 80 years if ?nothing changes?). It is seen that the ices of the North Pole (90° of Northern latitude, on the left on the figure) are the first concerned: at this time there, the average increase in temperature to the North Pole could go until 8° C!
The 3 differences mentioned above come can be explained with the same reason: the effect of greenhouse awareness2007 rises from the terrestrial radiation, which does not disparait the night or the winter. This effect is thus proportionally more important when there is no sun. Indeed, in the absence of our star of the day, the direct effect of the solar heating does not exist any more (or is low in winter), while the indirect effect of heating of the ground coming from the effect of greenhouse awareness2007 décroit less quickly. This fact the relative effect of its increase (of the effect of greenhouse awareness2007) is more sensitive when there is no sun (in winter and the night). Another process goes in the same direction: when there is no sun, the air is colder, therefore drier, and the ?natural? effect of greenhouse awareness2007 of to the steam is weaker. Consequently, the additional effect of greenhouse awareness2007 of to the increase in CO2 in the air (which is distributed in a way homogeneous and independent of the temperature) is proportionally higher where the temperature is low. That explains part of the increase in temperature more marked close to the poles.
on the continents (in opposition to the oceans), because the thermal inertia of the great water masses is much higher than that of the ground; a factor 1,5 being perfectly possible enters the total increase and that above the continents of the Northern hemisphere. That means that for 3 °C increase in the average temperature, which is the median forecast (?medium?) for 2100, we could have close to 5° C of average increase above the continents. And that to say when it is known that the average temperature could go up from 8 to 9 °C from here at 2 centuries! They are major variations taking into consideration what one knows of the climate of the past.
