## The environmental consequences of SIGIR

As it is becoming apparent that, without drastic immediate action, we are going to significantly overshoot greenhouse gas emission targets and warm the planet by an environmentally disastrous 4 to 5 degrees centigrade by the end of the century, I thought I should fulfil my long-standing promise to myself and calculate the carbon emissions generated by the annual SIGIR conference. I'm only going to consider here the emissions caused by air travel; but this is likely to be the overwhelming majority of total emissions.

SIGIR attendance varies from year to year: 610 for 2009, 553 for 2010, 800 for 2011, and 500-odd for 2012. Let's take 600 as a rough estimate of average attendance. Attendance was 50% in-continent in 2011, 40% in-continent in 2010, and 60% in-continent in 2009 (for, respectively, Asia, Europe, and North America). Let's say 50% in-continent and 50% out-of-continent.

Let's take Chicago--Los Angeles non-stop round-trip as a representative in-continent flight, and Frankfurt--Beijing non-stop round-trip as a representative out-of-continent flight. According to the emissions calculator provided by the International Civil Aviation Organization, the former trip generates around 480kg of CO2, the latter around 1,200kg. (We're being conservative here and assuming everyone flies economy, and everyone can make a non-stop trip. You can add roughly 200 kilos of CO2 per stop). Therefore we have (480 * 300 + 1200 * 300) = 504 metric tons of CO2 gas.

So how much is 504 metric tons of CO2? The US EPA provides a handy calculator of greenhouse gas equivalences; according to this, 504 metric tons of CO2 is equivalent to the annual emissions of around 100 US passenger vehicles; the energy use of 44 US households; 5 acres of deforestation; and so forth.

What could be done to cut these emissions? The simplest answer would be -- cancel SIGIR (though in practice this would probably lead to an increase in compensatory air travel for meetings that take place at SIGIR). A less drastic solution would be to move towards a model in which conference attendance is not compulsory for publication; something like the journalized conference form of the Proceedings of the VLDB Endowment. Journalization would reduce conference attendance (and resulting travel) to those who actually want to attend the conference (as well as removing a financial hurdle to publication for those who have limited finance). Additionally, if a series of three conferences were associated, on equal footing, with the attached journal (perhaps SIGIR plus CIKM plus one other), and if one such conference was held in each region per year, distance flown by attendees would likely drop.

As a not-for-profit organization, SIGIR is not subject to the profit-maximizing imperatives of business entities. The SIGIR community should be taking the lead in implementing practical solutions to reduce the environmental impact of its activities. Restructuring the way SIGIR and associated conferences work can help to achieve this.