This year the pandemic has shifted the dynamic of our working lives, with many of us spending the majority of the year working from home. At the same time, it has focused attention on the issue of climate change. As lockdowns brought air travel to a halt, global CO2 emissions saw an abrupt drop of 8.8% in the first half of 2020 compared to the same period in 2019, according to Nature Communications.

This raises a natural question: what is the carbon footprint of holding a large-scale physical event such as the International Congress of Mathematicians compared to the carbon costs of holding the same event online? If we assume that around 5,000 people would attend ICM in St. Petersburg for nine days (July 6-14) in 2022, how much carbon will this event emit, and how much of this could be avoided if the conference were held online? Clearly, a real-life conference will have a higher carbon footprint, but by how much?

First, let“s take a look at everything that is involved in a real-life conference compared to a virtual one. The largest contributions in terms of carbon emissions will come from attendees traveling to the conference. According to artificial intelligence specialist Neural Corporation, other things to consider include the carbon footprint of the hotel rooms, the conference venue, the digital equipment needed, running the kitchen, delivering food and beverages for all attendees, and other miscellaneous costs.

Since the majority of CO₂ will come from travel, let“s start with this. For the ICM conference in St. Petersburg, we can make an assumption that 25% of all attendees will come from the US, 25% from Europe, 25% from China, and the remainder from the rest of the world. It takes about 11 hours to fly from New York to St. Petersburg, 3 hours from London, 12 hours from Shanghai, and a miscellaneous time from other parts of the world (including short-haul flights from within Russia). For argument“s sake, let“s pick an average time of 5 hours for this last group.

According to an online flight carbon calculator, the carbon footprint per passenger flying 14,300km from New York to St. Petersburg and back will be 2,200kg. From London it“s 767kg per passenger (return), from Shanghai and back is 2,300kg. Let“s imagine the remaining attendees are flying in for 5 hours from Athens, amounting to a carbon footprint of 888kg her passenger for a return flight.

So if a quarter of attendees take the flights of each duration, we have 1,250 taking each. The formula is for calculating the total carbon footprint of 5,000 attendees traveling to ICM will then be:

(2200×1250) + (767×1250) + (2300×1250) + (888×1250) = 7,693,750 kg CO₂.

In addition, according to calculations made by Don Balanzat, laboratory coordinator at Arizona State University in an article for Educators in VR, the total energy needs of such a conference and the accommodation needed for participants for nine days would be 799,317 kg, taking the total emissions from the real-life ICM conference up to 8,493,067 kg. Meanwhile, for a nine-day virtual conference for 5,000 participants, his estimates suggest the total emissions would be 186,624 kg. So holding ICM online instead of in the real world would save 8,306,443 kg of CO2 emissions.

It obviously looks like a big number, but it can be hard to visualize what it really means in real-life terms. Luckily, there are various greenhouse gas equivalence calculators online, such as this one, which can help us make sense of this number. The emissions savings in this instance are equal to 1,795 passenger vehicles driven for one year or 959 homes” energy use for one year, for example.

Estimating the carbon footprint of an event is not an exact business, since there are many variables to consider, some of which may be unknown. Thus, for example, Mark Swartz, CEO, and founder at Neural Corporation, estimates the carbon footprint from travel could be as high as 2,050 kg of CO₂ for every person traveling by plane, so this alone would contribute 10,250,500 kg of emissions if everyone flies in.

Estimates of the carbon footprint of a virtual conference are equally varied. According to a paper published by Dennis Ong, Tim Moors, and Vijay Sivaraman at the School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney (Title: Comparison of the energy, carbon and time costs of videoconferencing and in-person meetings) the total cost of video conferencing takes at most 7% of the energy/carbon of an in-person meeting (the majority of this coming from electricity consumption of various devices and electricity generation systems).

It seems like a no-brainer that videoconferencing is a much better choice for the environment.

However, the authors of the paper note that “when time costs are considered, the cost-benefit that videoconferencing has over the in-person meeting is reduced because of the time overhead required to achieve the same functionality as a corresponding in-person meeting”. According to the paper, while attending video conferences means participants save on travel time, “past research has shown that participants who meet remotely using video communication technology take longer to complete the same task than those who meet in-person”.

Even more importantly for ICM 2022, however, is that virtual conferencing detracts from the key goals of the event. The aim is to encourage learnings about innovations in mathematics, sharing ideas and discoveries, and allowing the participants to meet the rising stars of mathematics. In addition, an important goal is to showcase Russian mathematics and Russia itself, including its culture and heritage. All of these goals are extremely important for the growth of mathematics as a field but impossible without real-life interaction.

So are the carbon emissions savings from holding the conference remotely worth the sacrifice? How do you quantify the loss of innovation and learning from a carbon intensity point of view? This is a complicated and multi-faceted discussion that should be continued on social media. All interested parties are therefore invited to an online debate on this topic on Twitter.

*by Anna Fedorova*