Chat:

Pablo Canziani: Sorry for the interruptions, I had a few problems with the connection Moderator: I suggest we begin by asking questions to Dr. Canziani, and then address Dr. Molina when he joins.

Ari: I have a paper by EPA saying that less ozone is destroyed if the stratosphere is cooler! Can you comment on that?

Pablo Canziani: That is not true actually.

Christian Marquardt: I would like to know in which way the ozone problem and climate change interact.

Ari: Is it clear that cooler stratosphere increases ozone destruction or is it still uncertain?

Pablo Canziani: There are a number of processes involved. One is the cooling of the stratosphere as a result of the reduction in ozone content. Then the possible modifications in stratospheric dynamics due to the change in ozone distribution. For example it is argued that the polar vortex over the Antarctic, which confines the ozone 'hole,' takes longer to break in the spring due to additional cooling resulting from major ozone depletion in the region. Ozone is a powerful greenhouse gas. The change in stratospheric dynamics is now thought to affect the tropospheric dynamics because of the resulting changes in the dynamics. Recent climate modelling has suggested ozone reduction has masked growing temperature increase in the troposphere due to GHGs by 10-24% depending on the model used.

Ari: Now I am really puzzled.... You mean that ozone destruction leads to cooling and not vice-versa?

Christian Marquardt: I remember that a few years ago it was not clear if the net effect of ozone destruction adds to or diminishes the greenhouse effect.

Pablo Canziani: The results I am mentioning, by Bitanja et al. J. of Climate 1997 consider the net effect of cooling resulting from stratospheric ozone depletion and the heating resulting from the CFCs. The balance of these two processes results in the figure I mention. Furthermore, recent results from the Hohenpeissenberg station in Germany do suggest that the tropopause height has changed. This increase in tropopause height is accompanied by changes in the ozone profile in the lower stratosphere.

Christian Marquardt: True - that could be a result of circulation changes and would yield lower total ozone values.

Pablo Canziani: The issue is: are these changes, which can be significant from the climate point of view due to the decrease in ozone that leads to a cooler stratosphere? Or as Christian has pointed out due to changes in circulation. We need to reach a better understanding on this issue. Regarding the GHG's in the troposphere, there are two effects. One is dynamic: a heating of the troposphere leads to a cooler stratosphere. The other refers to chemistry. Increases in methane and nitrous oxide can complicate the recovery of the ozone layer if the Montreal Protocol is abided by. Methane is destroyed in the middle/upper stratosphere and generates water vapour. Some argue that the cooling resulting from the warmer troposphere and the reduced ozone could extend to middle latitude heterogeneous reactions outside polar regions and result in a positive feedback on the system. I think Dr. Molina, who is a chemist can comment on this

Moderator: Professor Molina has joined us. Please address your questions to him too.

Mario Molina: The effect might be greater in the polar regions but with this feedback it would extend to lower latitudes.

Pablo Canziani: Another issue that was discussed at the SPARC SSG meeting a couple of weeks ago, was that of the processing of GHG's in the upper troposphere resulting from enhanced UV radiation. Our current knowledge on this process and the exchange of trace gases between the stratosphere and the troposphere is still limited.

Christian Marquardt: The enhanced UV radiation also increases radiative forcing in the troposphere...

Ari: So is the role of the PSC's diminishing?

Pablo Canziani: The role of PSC's has not diminished. On the contrary with enhanced cooling in polar regions in the vortex confining the ozone hole there are increased occurances of PSC's

Moderator: Is the ozone layer issue and the way it was addressed internationally useful as a lesson for the broader issue of climate change?

Ari: Why is UV increasing radiative forcing in the troposphere?

Pablo Canziani: UV radiation is important in meny tropspheric chemical reactions that affect GHG's eg the creation of tropospheric ozone

Ari: How about effects of UV on algae?

Pablo Canziani: Some ocean biologists have published results that show in the South Atlantic the enhanced UV radiation has had impacts on productivity indices. Some biologists mention a reduction of as much as 20-30% in the Austral Spring. This is probably mostly due to the impact on phytoplankton.

Christian Marquardt: And in which way can procedures taken from the Montreal protocol be used to deal with the climate problem?

Pablo Canziani: The ozone issue addressed refers to stratospheric ozone, also known as the good ozone. The tropospheric ozone issue, aka "the bad ozone" remains to be dealt with. Regarding the Montreal protocol, in many aspects it was a simpler issue that could be much more easily handled and its links with politics and industry were much better defined. This resulted in a more expedient handling of the policies. Now the current ozone issues like tropospheric ozone and the impacts of aviation both in stratospheric and tropospheric ozone are far more complex.

Ari: Did the industry causing the ozone hole problem benefit from the Montreal protocol?

Pablo Canziani: I am only inlvolved in the science of the stratosphere, not in the aspects of the results of the Montreal Protocol upon industry. All I can say that the targetted segment of the industry was much better defined.

Moderator: Pablo, could you just recap the issues that we covered for Prof. Molina?

Pablo Canziani: Certainly. We have discussed the relationship between the changes in the ozone layer and changes observed in the dynamics of the stratosphere and the tropopause. We also very briefly mentioned the issue of GHG's (methane for example) impacting on the ozone layer, in a way that could result in a slowing of the recovery of the ozone layer, and a longer period of stratospheric changes impacting climate.

Moderator: Thanks. So that is one link between the ozone layer and the broader issue of climate change. The Montreal Protocol was (and is) science driven. So is the Climate Change process, with the work of the IPCC.

Pablo Canziani: I would add that for many years atmospheric scientists thought studying the troposphere was sufficient. Mounting evidence suggests the troposphere and stratosphere should be handled as a single more complex unit.

Moderator: How do you see the role of science evolving as these processes evolve?

Pablo Canziani: On the one hand there is the need to improve General Circulation Models, including simulation of the stratosphere both from the point of view of dynamics and chemistry.

Mario Molina: Many uncertainties remain, but science still plays a critical role

Pablo Canziani: There is also a need to enhance the monitoring capabilities to reach a better understanding of the stratosphere globally. It is interesting to note that the US weather service and the Israeli weather service are experimenting the inclusion of stratospheric ozone data to improve their weather forecasts on a 5 day range.

Christian Marquardt: I believe the general assumption about ozone is that he problem will be solved in, say 50 years from now because CFC emissions have been reduced. Why is it then so important to continue science in this area?

NASA: CFC's you mean to stop using it right? What about the pressure from politicians and industrialists?

Ari: I would like to take the chicken and the egg issue up again. Is the role of ozone depletion on global warming more important than the role of GHG's on ozone depletion? Is the ozone layer currently recovering or becoming worse affected?

Pablo Canziani: We cannot yet say when the layer will start to recover. An answer to that will come within the next 10 years. As for the role of GHG's they can affect the recovery and this leads to a climatic feedback according to our current knowledge.

Mario Molina: It is very important to continue monitoring the recovery of the ozone layer, to confirm our understanding. It appears that the recovery of ozone will be delayed because of GHG -induced cooling of the stratosphere, however, the concentration of CFCs is already beginning to decline - a very important first step.

Pablo Canziani: In reply to Christian, the forecast about the ozone recovery in 50 years is based on 2 assumptions:

1. That all parties fully abide by the Montreal Protocol

2. That the composition of the atmosphere remains as it is today.

However, the European Commission has questioned the validity of the 2nd assumption.

Christian Marquardt: You argue that the change in GHG concentration radically changes (heterogeneous, I guess) ozone chemistry?

Moderator: In a sense, I'm asking the following: At some point we will cross the threshold from where prediction (emphasis on models and data) needs to be improved to where monitoring (emphasis on measurements) needs to be improved.

Pablo Canziani: Also, as I have previously mentioned the mass transfer between the troposphere and the stratosphere can be a significant sink for certain GHG's.

Ari: Would ozone depletion happen without the presence of PSCs?

Mario Molina: Monitoring is essential to test models. But we need predictions to aid regulatory decisions.

Moderator: We are not there yet with GHG's. But what about CFC's, which is a more mature process? For CFC's are we at a stage where the predictions are sufficiently well understood to put the emphasis on monitoring? Or do we need to continue to emphasise both?

Pablo Canziani: Regarding CFC's the surface measurements do superficially show a negative trend. However stratospheric processing of these gases is very slow and the complete cycle from the time an air mass enters the stratsophere in the tropics until the time it reaches the poles is of the order of 2-3 years.

Mario Molina: PSCs are essential for polar ozone depletion, but not for the upper stratosphere low latitude losses that have been also observed. The main delay in the recovery of ozone is a consequence of the long residence time of the CFCs

Christian Marquardt: Dr. Canziani, but elaborating on the moderator's question somewhat further: What about the possible climatic effects of the substitutes for CFCs?

Pablo Canziani: I do not have the exact figures but the HCFC's and HFC's are significantly strong GHG's, at least as strong as the CFC's.

Mario Molina: The climatic effects of CFC substitutes are not as important as those of the CFC's, because they do not accumulate as much

Pablo Canziani: The Montreal Protocol includes revision of the use of the replacement gases and contemplates their phase-out during the first part of the 21st Century.

Mario Molina: A major advantage of the HCFCs is that they have shorter residence times because they are less stable.

Pablo Canziani: So their net effect would be smaller.

Christian Marquardt: I see. So there isn't any danger that the solution of the ozone problem will have negative consequences on the global climate?

Pablo Canziani: Well, the 1995 Ozone Assessement Report pointed out that the recovery of the ozone layer could result in an enhanced tropospheric temperature increase. The values mentioned in that report and also the values quoted by the IPCC mention that the magnitude of the temperature change due to the ozone layer recovery are of the order of 0.1-0.2 deg. C.

Mario Molina: The effect on climate from CFC substitutes is a second order problem. The effect of CFCs is a first order problem.

Ari: Why did US want to take HCFCs, PFCs and SF6 into the Kyoto protocol while the EU did not?

Moderator: The response to Ari's question, I guess, has to do with the industrial policies of these countries.

Mario Molina: PFCs and SF6 are very long-lived - the US thought all important GHGs should be included.

Moderator: Can someone address the issue of the way industry responded to the Ozone issue. One of the issues discussed here at COP4 is how to involve the private sector and industry in the process to reduce GHG emissions worldwide.

Pablo Canziani: I beleive Dr. Molina should answer that since he spearheaded the issue for over a decade!

Mario Molina: The CFC problem was solved with the participation and collaboration of industry. This is a very important lesson for the climate change issue.

Ari: Was industrial collaboration due to the financial benefits of the Montreal protocol?

Moderator: How did this happen? What were the mechanisms involved?

Mario Molina: Industry was initially reluctant, but eventually became very active toward finding solutions. As long as they perceive a level playing field they are ready to collaborate. Financial benefits played a role, but so did the public relations issue of not being perceived as a polluter.

Christian Marquardt: In the O3 problem, industries found substitutes - what would be the equivalent in the climate discussion?

Ari: Restructuring of the energy industry

Moderator: I would guess clean technologies...

Mario Molina: Of course, it is difficult to find replacements for fossil fuel -- it is so cheap! Therefore, powerful incentives to develop new technologies are needed.

Christian Marquardt: I wonder - did industries invent substitutes because of some external pressure, or did it just happen and make some political improvement possible?

Mario Molina: Substitutes were developed because of the environmental issue and because of the potential to make money assuming regulations were enforced. The formulation of new regulations provides the incentive for clean technologies -- economic incentives alone do not work.

Pablo Canziani: I agree with Dr. Molina. The issue of aircraft emissions clearly shows that when it is difficult to focus on the science problem and find significant incentives for industry the issue modification process is very slow.

Moderator: So in other words, industry requires a level playing field but at the same time some incentives to participate, e.g., improved image or increased profits.

Moderator: Well, one way of addressing this issue is to travel less and interact electronically.

Christian Marquardt: But at present, personal communication is much more effective than chatting!

Moderator: I would like to say that our scheduled chat will end shortly. I'd be grateful if the participants could sum up their comments.

Pablo Canziani: Rounding up from my perspective, since we are now coming to a close, the discussions at the SPARC SSG concluded that we must focus on the stratosphere as a system of which the ozone layer is a significant part.

Mario Molina: It is important to consider the whole system, taking an integrated approach. Global warming, ozone depletion and pollution of the troposphere -- all interact with each other! The CFC-ozone issue taught us that global problems can be solved. The greenhouse issue is harder to solve and much less certain, but we have a precedent! Thanks to all.

Pablo Canziani: This implies a strong commitment to improve the models and to improve our monitoring capabilities at a Global Level. Thanks to all!

Ari: Thank you very much, prof. Molina, for the INSPIRATION!

Moderator: Thank you all for your comments. Thank you Prof. Molina for your work which has set the stage for the precedent you mention. Goodbye and please join us again for our forthcoming chats at COP4.