The graph shows that over 60% of roughly 200 survey participants were in favour of the new format. Satisfaction was highest in La Plata, where most participants would not have been able to attend a traditional conference (at a single location in Europe or North America) for financial reasons. Satisfaction was lowest in Montreal, to which many US participants flew. Evidently, many North Americans would have preferred to fly to Graz for a single-location conference.
A possible solution for the future is to promote the following two types of equality:
- Equal distances between time zones. Montreal was relatively close to European time zones and relatively far from Sydney. A Western American hub would have solved this problem. The participants at such a hub would have felt better integrated, finding it easier to follow presentations from Graz in the morning and from Sydney in the late afternoon.
- Equal number of participants at the different hubs. The hub in Graz had about twice as many participants as Montreal. The participants in Montreal would have felt more involved in the conference if these two hubs had been more balanced. Nevertheless, the participants in La Plata and Sydney also enjoyed the conference, although these hubs were even smaller.
Discussion. Evaluation sessions took place on the last two days of the conference. The meetings in Graz and Sydney took place onsite, while La Plata and Montreal participated virtually. A moderator introduced each session. The audience then discussed the advantages and disadvantages of the new conference format and other possible formats. A student assistant took the minutes and the moderator gave a brief report at the final session of the conference.
Calculation of CO2 footprint. The effective carbon footprint (greenhouse gas emissions) of the conference due to air travel was estimated based on information provided by participants at registration (Graz only) and the distance of their home institution from their hub. The result was compared with estimated emissions of previous conferences in the ICMPC series. The calculations were carried out in collaboration with the Wegener Centre for Climate and Global Change in Graz.
In a preliminary estimate, we calculated the direct distance as the crow flies between the place of work (affiliation) and the attended hub for each participant. Emissions were estimated based on the main mode of transport. At the registration desk in Graz, 178 participants indicated that they had mainly travelled by plane, 44 by train, 13 by car, and 9 by bus. A few of those had flown from outside Europe (mainly North America). Emissions were estimated using published European emission factors: 0.285 kg CO2e per person-kilometer for flying, 0.101 for driving a car, 0.068 for bus, and 0.014 for train. For other hubs, we assumed surface travel if the affiliation coincided with the hub’s metropolitan area (Sydney, Montreal, or Buenos Aires) and air travel otherwise (so total emissions were slightly overestimated). We also calculated emissions for an equivalent single-location conference in Graz to which all non-Graz participants flew.
The total distance traveled in the multi-hub configuration was 2.52 million kilometers. If all participants had traveled to Graz, the total would have been 5.95 million kilometers. Therefore, the multi-hub format reduced the total distance traveled by 58 %. The corresponding reduction in emissions was (at least) 59 %, from 1663 to 684 tonnes CO2e. The reduction in emissions was greater than the reduction in distance, because people travelling shorter distances were less likely to fly. On average, the multi-hub format reduced emissions by 2 tonnes CO2e per person, from 3.3 for the single-location format to 1.3 for multi-hub.
Emissions could have been further reduced in several ways:
- The North American hub was in Montreal. A more central location in North America would have reduced emissions while at the same time reducing the time difference between the North American and Australian hubs.
- Alternatively, there could have been two North American hubs (e.g., East coast and West coast, or NW and SE, or NE and SW). In that case, many North American colleagues could have avoided flying altogether.
- Many Graz participants flew from European locations, although they could reasonably have traveled by train or bus. We could have not only encouraged, but also rewarded them for using low-carbon transport.
- Some participants perceived Graz to be the main hub and flew to Graz from other continents, especially North America. To prevent that, we could have made it clearer that there was no central hub.
- Graz could have been made less central by adding a second European hub (relatively far from Austria, e.g. Spain, UK, Finland, Poland, Greece). That would have reduced the size (number of participants) of the Graz hub and made hubs more similar. Even better, the Graz location, which is close to the center of Europe, could have been abandoned in favor of two locations that are neither central nor peripheral, e.g. France and Poland, or England and Italy. More peripheral countries such as Greece and Finland are currently harder for most Europeans to reach without flying; Spain and Scotland at least have train connections.
- Additional hubs in the Global South – not only Argentina, but also India and South Africa – would have opened the conference to a greater number of colleagues without increasing emissions per participant.
If such policies had been pursued more consistently, the reduction in emissions per participant relative to a traditional single-location conference would have increased from approximately 60% to approximately 70%.
In the following diagram, the horizontal axis represents emissions per participant. The vertical bar at "8000 kg CO2-equivalent" represents the number of participants who emitted between 4000 and 8000 kg CO2-equivalent while travelling to and from the conference. The figure divides flying participants into two groups. Around 190 (on the left side) were short-distance flyers who emitted less than one tonne of CO2 equivalent per person or travelled by bus or train. Around 50 (on the right side) were long-haul flyers who emitted more than four tonnes of CO2 each.
