Data witnessing: making sense of urban air in Copenhagen, Denmark

Taking air pollution in Copenhagen as a case of environmental change, this article discusses the different ways that data are employed in processes of witnessing this change. We distinguish between three different modes of “data witnessing”—modest, imperial, and guerrilla—in order to clarify how different scientific, corporate, or civil society actors are engaged in producing and analyzing data about air pollution from different vantage points and with different interests. Their respective data work, as well as their joint participation in collaboration and confrontation over the interpretation of data, is a crucial component in making sense of air pollution in Copenhagen, which is predominantly out of reach to the human senses. Witnessing air pollution in Copenhagen is made possible by critical data designs under circumstances where neither data, nor subjective witnessing, in itself is enough.