Background
The authors write that "marine ecosystems in the northeast Atlantic have warmed particularly rapidly, with mean sea temperatures in the North Sea and Celtic-Biscay Shelf regions increasing between 1982 and 2006 by 1.31°C and 0.72°C, respectively," which is four times faster than the global average. And in light of these facts, they considered these regions and timeframe to be ideal for determining how real-world fish respond to real-world warming.

What was done
Simpson et al. say they "assessed the full impacts of warming on the commercially important European continental shelf fish assemblage using a data-driven Eulerian (grid-based) approach that accommodates spatial heterogeneity in ecological and environmental conditions." This they did by analyzing "local associations of species abundance and community diversity with climatic variables, assessing trends in 172 cells from records of >100 million individuals sampled over 1.2 million km² from 1980-2008," rather than relying on macro-ecological analyses of the effects of climate change on marine fish assemblages (as is done with the climate envelope approach) that do not account for "constraints on distributional shifts due to population dependence on essential habitat, such as favored substrates, appropriate predator and prey fields, and close proximity to nursery grounds, all of which are often unknown and difficult to quantify."

What was learned
The seven scientists say they discovered "responses to warming in 72% of common species, with three times more species increasing in abundance than declining," and they say that they also found these trends "reflected in international commercial landings," where landings of nine species identified as declining in warm conditions fell by a half during the period of their study, whereas landings of 27 species identified as increasing in warm conditions rose by 2.5 times. In addition, they indicate that this "profound reorganization of the relative abundance of species in local communities occurred despite decadal stability in the presence-absence of species," such as would have been suggested by the climate envelop approach on a larger spatial scale.

What it means
Simpson et al. state that their "finding of stability in presence-absence of species over decadal periods, but significant temperature-driven responses in local species abundance and assemblage composition, suggests that climate envelope models based on species presence-absence alone will not predict the most ecologically and economically significant effects of climate change."