"THIRD ASSESSMENT REPORT IPCC"
"Summary for policy makers : a scientific support always adequate to the urgencies of the Kyoto's global negotiations ?"

Maurizio Michelini
ENEA - Casaccia Research Centre, Rome

Key concepts in the evolution of greenhouse effect

The Intergovernmental Panel on Climate Change ( IPCC) , the UN scientific body for the study of climate evolution , has recently published the "Third Assessment Report" /1/ that contains the results of the simulations relevant to the Global Worming. The graphics show the growing concentration of CO2 and of the average global heating within 2100 in connection with 7 different CO2 emission scenarios. (Fig. 1)
The text does not give a clear explanation of this temporal limitation, but probably the cause lies in the reliability problems of complex simulations based on models of the carbon cycle and of the climatic consequences that are still uncertain.
To recall the attention of policymakers on the risks correlated to global heating, in the " Summary for policymakers" the increases of global temperature within 2100 are stressed. These vary from a minimum of 2,0°C to a maximum of 3,7°C depending on the chosen emission scenario.
In one case , corresponding to the scenario "Emphasis on fossil sources", the increase in temperature reaches even 4,4°C. But the scenario in question (that foresees for the end of the century an increase of CO2 emissions equal to 4 times the current figure!) is considered, luckily, improbable being related to the lack for an entire century of a set of proper emissions rules.

In order to assess the importance of the temperature increases in terms of global risks, one can read in IPCC's Assessment Reports the description of the harmful effects that the climatic changes have on the biosphere. For the time being it is enough to remind that the atmospheric disasters that in the last 20 years have increasingly struck the planet, are correlated to an increase of the global temperature DT equal to approximately 0,4°C.(Ref. 1, Fig. 1a)
A recent report by UNEP (Nairobi,5th February 2001) states that the increase of the atmospheric disasters in horizon 2050, in front of an average DT equal to 1,0¸1,5°C, could have an annual cost of 300 billion $ , whereas the annual cost of sanitary measures will increase by 30 billion $ in the USA and 21.9 billion $ in E.U. In 1990 the insurance cost of atmospheric disasters has been equal to 40 billion $.

In our opinion, the Summary's result description does not appear to be suitable to induce a correct risk perception. It is possible to see this confirmed by the fact that, at opinion maker level, the case of DT=4,4°C relevant to an unlikely scenario (therefore with reduced risk) is cited as example of great climatic risk, whereas the fact is ignored that all others simulations due to likely scenarios, show, when extrapolated beyond 2100, much higher DT values (great risk).
We have already recalled that, from a purely scientific point of view, there are valid reasons to cut down graphics to 2100. But, from the point of view of Kyoto's negotiations, there are even more valid reasons that would advise a less "timid" attitude of IPCC.
It would certainly be appropriate to produce in decisional seats (such as the Conference of Parties) the graphics subsequent to 2100 of the simulations performed with the most reliable physic models and scenarios.
An example will clarify this opportunity. Some preliminary simulations (Rif. 2) show in connection with the emission scenario denominated Heavy (in intermediate position among the scenarios studied by IPCC, (see Fig. 1 bis) that the CO2 concentration will continue to grow reaching after about 4 centuries a peak comprised between 1250 and 1340 ppm (Fig. 2 ), while the global temperature will reach ( compared to now) a DT peak equal to 8,2¸9,0°C.
For the already mentioned reasons, the peak values are subject to marked uncertainties.
As a consequence, after the peak , the curves have no practical significance. Yet, the graphic has not been broken off in order to concretely demonstrate the influence of a double hypothesis model of the ocean absorption.
The first part of the simulation (which is the more reliable) in substance says that the irreversible damages to the planet will start long before the peak of temperature is reached.
The comparison with the IPCC's results (Fig. 1) can be done by observing that the increase in temperature within 2100 of this simulation (2,5°C compared to now), is positioned within the group of intermediate results. Therefore it is not an extreme condition simulation.

Let us now consider a great global intervention such as the safe storage of CO2 discharges (or their equivalent reduction) regarding a growing fraction from zero up to 30% during peak of discharges around 2070 - 2080. This intervention has been simulated in Rif. 2 ( Fig. 2 bis ),
If we limit the survey of results within 2100 we will discover that the intervention is capable of reducing DT at the end of the century from 2,5°C to 2,3°C. But if we protract the simulation (assuming that the reduction of CO2 emission will continue after 2100 ) we will discover that the peak of temperature will decrease from 9,0°C to more or less 5,8°C.
It is clear that the risk abatement is much improved!
On the basis of the results within 2100 one would say that intervention is practically useless, whereas long term results tell us that the biosphere would pass from certain destruction to hope of recovery ( through a series of interventions ). And yet it is the same intervention !
It is, therefore, not exaggerated to say that the real negotiations on global heating will start when IPCC will decide to publish (with the necessary caution on the uncertainty of calculations) the results of simulations after 2100!

Now let us try to understand, beyond the technicality of simulations, the physic reasons why the global heating becomes more insidious when its foresight moves away.
The strong delay (at least 3 centuries) in reaching the temperature peak, could induce us to believe that there is more time at our disposal for contrast interventions. In reality the delay is associated to an increase of the risk, because the further the peak moves away, the higher it becomes.
This characteristic of the carbon cycle can be explained, from a physic point of view, keeping in mind that during the phase of concentration growth in the atmosphere, saturation phenomena gradually take place in the biological and physical processes that determine the absorption of CO2 in oceans. Then, in certain conditions, absorption can diminish.

How much CO2 can be discharged without compromising the biosphere?

The above mentioned general concepts consent a simple and effective evaluation of the risk when they are confronted with the experimental measures of the CO2 concentration in the atmosphere, that has grown from 315 ppm in 1958 to the current 370 ppm.
The IPCC experts have ascertained /3/ that the cost relevant to global interventions in order to reduce CO2 emissions, increase abruptly when the aim is to stabilise CO2 concentration at levels inferior to about 550 ppm. In other words, because of the time lost, we are no longer in the possibility to stabilise the phenomenon at concentrations around 450 ppm.
Therefore our aim must be shifted to the threshold of 550 ppm /4/. In this case humanity can't do anything else but prepare its development programmes so that the quantity of CO2 in the atmosphere does not exceed this level, corresponding to about 4300 Gt.
C.D.Keeling, in the station of Mauna Loa ( Hawaii ) has monitored, starting in 1958, the monthly concentration of CO2 (Fig. 3). The average annual concentration has grown in a more or less exponential manner, that, projected into the future by means of simulation based on scenarios of intermediate discharge, allow to foresee the overcoming of 550 ppm within 50 ¸ 60 years.
At the end of the century the concentration will have reached 700 ppm!
The time remaining for interventions is decidedly scarce. No global intervention, even if extended for 60-70 years, will be able, if started too late, to limit the concentration at the desired level.

Let us gradually approach the problem of calculating how much CO2 can still be emitted without overcoming the threshold of 550 ppm. Currently 2890 Gt are present in the atmosphere.
Supposing that there is no absorption in the oceans, there would be place in the atmosphere for only (4300 - 2890) = 1410 Gt of CO2.
In reality one can deduce from Kealing's measurements that the ocean absorption, equal to an average 48% of emissions in the decade 1958 - 67, has increased reaching in the decade 1987 - 96 an average of 52%. We know that this absorption is increasing, but we do not know with certainty what value it might have within a century, or if later it will decrease.
This is why the studies on modelling relevant to carbon cycle in the biosphere, that have not yet reached complete comprehension of the phenomena, are very important.
Therefore one can answer the key question ("how much CO2 can still be emitted counting on ocean absorption") only with the use of models.
From the surwey of the preliminary simulations /2/ we can find that an average 63¸67% of the CO2 quantity that will be emitted from now to the peak (critical emission), will be absorbed by the oceans and therefore only about 1/3 will remain in the atmosphere, thus increasing the concentration.
Consequently, the maximum quantity that we are allowed to emit without endangering the biosphere equals about 1410 x 3 = 4200 Gt.
This increase in receptive capacity of the biosphere is important, but not conclusive.
Critical emissions depends obviously from the type of scenario.
In Rif. 2 a long-term scenario is considered (named Timely) that shows short-term consumes (that is within 20 years) about 20% lower in comparison with today's most credited scenarios.
The emission curve of this scenario is rather contained (Fig. 1bis) in correspondence to a qualified energy development such as to allow a sufficient economic development of the world population.
But even in this scenario the critical emission is too high : approximately 9600 Gt of CO2!

The cause can be found in the slowness of the diffusion of renewable sources and in the persistent use of fossil sources. The concentration peak, placed in over 3 centuries (Fig 4), is between 750 and 795 ppm.
Thus, even assuming that the world will enter a low emission scenario, to fall within the limit allowed of 550 ppm one must foresee additional specific interventions capable of halving the critical emissions.
Now, it certainly appears necessary to prepare an effective strategy in order to guarantee the capacity of storing in safe ways an adequate fraction of globally produced CO2. To give an idea of the proportions and costs of this world's strategy it is sufficient to remind that the CO2 quantity that will have to be restricted ( in deplete wells of gas, in acquiferous, etc.) is equal to 500¸600 times the quantity currently pumped by the USA in old oil wells to increase the retrievable oil fraction (programme Enhanced Oil Recovery - EOR).
Beyond the problem of the enterprise dimensions, the problem of a fair distribution of the whole cost has to be solved as well. (In the EOR programme no costs were involved, given the commercial convenience of the recovery ).

The evolution of Climatic Change and the Kyoto negotiations

Attention is normally focused on the main greenhouse gas, since CO2 is currently responsible of 53% of the radiation forcing /1/ produced by the various greenhouse gases, which are (in decreasing order of contribution):
CH4 (17,2%), Tropospheric ozone (12,5%), Halocarbons (12%), N2O (5,3%).
But it is obvious that study of the atmospheric evolution of all greenhouse gases is of great importance, as well as the most suitable interventions for reducing their discharges.

The studies on the climatic changes performed by IPCC and other scientific national and international bodies proceed on a very vast front, but with a swiftness that appears to be low if confronted with the urgency of establishing a strategy of global intervention.
According to many scientists, it is necessary to go one step further, that will enable to answer in good time the following question: "When finally a global strategy will be approved, will we be in time to implement with success the proper interventions? "
One has to distinguish the scientific aspect of the problems (that request time and caution) from the decision making aspect, linked to the Kyoto negotiations, that request prominently (except suffering a setback, as we have seen) to know and evaluate the maximum level of risk.
Only in this way a correct response strategy can be formed.
Other doubts about the negotiation failure in The Hague can arise from the fact that some people have supported an adaptation strategy of humanity to the damaging effect of climatic changes.
This strategy, born too early, has caused amazement in a moment in which it is considered of high priority to define timely interventions that, having to be maintained for a long time, have to be activated (and therefore studied) in time.
Perhaps the unexpected adaptation strategy would not have been put forward if the most qualified sources, such as IPCC, had published the forecasts on the global temperature peak, that cancel any illusion on the possibility of adapting to climatic changes.
Recently, F.Bierman has resumed on Environment /5/ the proposal of a world Authority responsible for Environment, reminding that this proposal has been put forward in 1997 by the German government jointly with Brazil, South Africa and Singapore and resumed the following year by french president J.Chirac.
From the particular point of view of this work, this proposal appears appropriate since it would allow to relieve the scientific body (IPCC) from those elements of "self-censorship" introduced in the elaboration of the " Assessment Report" by scientists compelled by an all-pervading sense of responsibility.
Scientific documents, such as the IPCC Assessments, should publish (in order not to neglect worldwide needs and expectations) all data and calculations useful for the correct assessment of risk , with the sole obligation of scientific rationality.

References

1.- "Summary for Policymakers - WG1" in "Third Assessment Report IPCC -
March 2001

2.- M. Michelini, G. Giuli, G. Izzo, V. Pignatelli
" Un Modello puntuale per la Simulazione dell'Effetto serra in relazione a due Scenari di
emissione di CO2 con alcuni Interventi di limitazione dei gas serra."
ENEA - RT/ERG/2000/1 - June 2000

3.- "Summary for Policymakers - WG3" in Third Assessment Report IPCC -
March 2001

4:- "UK Climate Change Report" commissioned by J. Prescott, Secretary of State
for the Environment - January 2001

5.- F. Biermann - "Environment" n. 9 Vol 42 - November 2000