  We study the problem of identifiability of the total effect of an
intervention from observational time series in the situation, common in
practice, where one only has access to abstractions of the true causal graph.
We consider here two abstractions: the extended summary causal graph, which
conflates all lagged causal relations but distinguishes between lagged and
instantaneous relations, and the summary causal graph which does not give any
indication about the lag between causal relations. We show that the total
effect is always identifiable in extended summary causal graphs and provide
sufficient conditions for identifiability in summary causal graphs. We
furthermore provide adjustment sets allowing to estimate the total effect
whenever it is identifiable.
