, -intenational Cooperation on Investigation and Resean:h of Marine Natural Resoitn:e and Environment- _
PROBLEMS OF THE RECENT CLIMATE EVOLUTION THEORY R.I. Nigmatulln Shirshov Institute of Oceanology, Russian Academy of Sciences 36, Nahimovski prospect, Moscow, Russia, 117997 EmaiL [email protected]; Phone: -^7 (495) 1245996; fax: +7 (499) 124598}
Numerical modeling of climatic processes is based on the three-dimensional Reynolds-averaged Navier-Stokes equations (with scalar viscosity) taking account of the gravity and Coriolis forces (the equation of heat influx with scalar turbulent heat conductivity). These equations are solved for the ocean and the atmosphere proceeding from the real bottom and land topography. On the inter-phase boundaries (atmosphere-ocean, atmosphere-land), use is made of the empirical formulas (of parameterization) for heat exchange and stress between air and fluid, between air and hard land. Solutions are sought on a three-dimensional finite- difference grid of the ocean and the atmosphere size with the use of numerical codes for supercomputers. The smaller the grid cell sizes, the more precise and more detailed the solution but the more powerful the computer should be. Modern supercomputers make it possible to assimilate tens of millions of cells. This means that cell sizes are 10-100 km horizontally over the whole Earth's surface and about 0.1-1 km vertically.
The computer codes described were used to solve the initial problem at a time step of the order of 10 min with a successive calculation of all daily and seasonal variations. Parameters that determine phase transfer and interaction coefficients (ocean, land, atmosphere) in the climatic system were chosen so that numerical calculation be in conformity with the well-known history of the variations of climatic parameters (the distribution of average temperatures, pressure, precipitation). The choice was followed by a calculated forecast of the evolution of these parameters for different scenarios of anthropogenic C02 emission.
According to the calculations, we should expect global warming a considerable contribution to which will be made by anthropogenic C02 emission: the global temperature will show 1°C rise by 2030, and 2 ^ ° C rise by 2100, depending on the emission growth rate. The maximum temperate rise is predicted on land and in the high latitudes (in the Arctic 2°C rise by 2030 and 7.5°C rise by 2100). The same calculations show precipitation growth in the high latitudes and precipitation decrease in the subtropical regions.
In a few years more powerful computers that are expected to appear will allow for the assimilation of milliards of cells and the use of more detailed grids with cell sizes of 1-10 km horizontally and 10-100 km vertically which will make the
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calculations more precise. However this way without radical improvement of the numerical model will not allow to obtain more reliable results for the following reasons:
First, C 0 2 balance and turnover in nature, in particular, the increase of C02 reworking by the green mass of the ocean and land with a temperature rise is insufficiently substantiated and detailed;
Second, even a 10 times smaller difference grid (10 km x 10 km x 100 m) and its corresponding difference detalization are not sufficient to resolve the above- mentioned thin gradient zones abundant in the ocean which contribute essentially to heat transfer. And such difference grid requires more than a 1 000-fold increase of the calculation scope for which purpose a fantastic supercomputer is needed.
To overcome the obstacle it is necessary to solve the problem of the multiscale character of the ocean, to learn to identify and to calculate the "singularities" in the
Third, the above-mentioned detalization does not allows one to calculate mesoscale circulation currents which are 10-30 km horizontally and 500-1000 km vertically. Hence, the energy of these currents and their contribution to mass, impulse and energy transfer should be taken into account as energy of horizontal and vertical mesoscale currents or as undergrid turbulence. Its horizontal linear scale is ~10 km and vertical -100 m. Such turbulence cannot be isotropic and its transfer characteristics (viscosity, heat conductivity) should be determined not by a scaler but by a second-rank tensor. If cylindrical symmetry in the horizontal plane of mesoscale currents is accepted the transfer characteristics are determined by two main quantities of different orders of magnitude - horizontal and vertical viscosity (heat conductivity). Their values depend on the energy of small-scale (turbulent) currents, horizontal and vertical separately, which should be included into equations as two variables kinetically independent of the average current field.
That is, instead of the Navier-Stokes type equations one should use equations of the type of the k-E-model of turbulent currents;
Finally, fourth, an essential numerical modernization Is necessary.
The thing is that the intensity of the global temperature rise (1°C during tens of years which is 10-4°C/day) is negligible compared to the intensity of daily (to 10°C/day) and seasonal (lO-TC/day) temperature oscillations. The calculations described above are made using a small time step relative to a day (At ~ 10 min « 24 hours). Calculations for 30 years ahead require several millions of steps which results in the accumulation of calculation errors and too much time. To cope with the problem it is necessary to reveal minor changes of the averages at a great
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Workshop; -Intetnational ^.•.•r.^;n;vw;nlnvestitation and Research of Marine Natural Resoutce and Environmenf
number of periodic changes using the N.N. Bogolyubov averaging method with identification of slow and fast variables:
T(t, (p, w, z)= r((Bg,oba|f. f~ v. z) "^
+ ATJ^eason) ("globalf• <?. V . ^ j ^'"C^V'^O + + A f „ a y ) K l o b a l f . f. v . z ) S i " ( " V ) -
fOyear = I day"', "day = | day''. iBgi„tai = ecOy„, 8 « 1).
2jt 365 27t'
Here 9, v, i. are the coordinates of the ocean and atmosphere soze, -' is the average annual temperature, T, AT(season) „ AT^ay) ^^^ jj^^iy changing average annual temperatures and space distributed amplitudes of the seasonal and daily oscillations.
By summing up the above-stated, it necessary to emphasize that anthropogenic impacts on climate are very small compared to the natural impacts and climate changes under discussion are small as well. However, even these small climate changes can affect essentially the people's lives. The analysis of anthropogenic effects is insufficiently complete to make global macroeconomic decisions. Yet such an analysis is extremely timely.
In conclusion a question should be put: what is to be done under the threat of climate change if one believes that the anthropogenic factor is essential?
First of all, there is every reason to think that mankind will be able to adapt to climatic changes. The increase of fuel combustion and C02 emission Is expected to continue during several decades to come. The Earth's population has been growing and now approaches 7 milliard people, whereas 70 years ago it made up 2 milliards. As for the calls to cut the emissions, it should be noted that to-day 90%
of anthropogenic C02 emission is caused by only 25% of the Earth's population inhabiting the territories of the industrial countries. 'These territories embrace countries of North America, Europe (Russia included). Chin?. Japan, South Korea and a number of other countries. Per-capita use of energy (in oil equivalent) per year is 8.7 tons in USA, 4.2 tons in Europe and 2 tons in Russia. As is well known, the deindustrialization in Russia in the 1990th has resulted in a two-fold decrease in the use of energy.
For Russia, China, India and for those 75% of our planet's population whose per-capita "contribution" to C02 emission is small (like in Russia) or very small (like m China or India) the main problem is to overcome poverty. Therefore, is it
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possible to convince these countries that they should slow down their industrial development and to limit the combustion of coil and hydrocarbons? During recent year China constructs 50-60 GWt/year electric power facilities (the total capacity of the electric power stations in Russia, working mainly on coal, is 210 GWt). The reduction of C 0 2 and other harmful matter emissions at the expense of self- restriction in energy consumption and energy efficiency growth should be the task, first of all, of rich countries. In conclusion it is not out of place to recollect the original view on climate of the famous Russian writer M.E. Saltykov-Shchedrin who wrote: "Climate in Russia is good if the governor is proper".
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