Schematic diagram of emergent constraint technique.

Note: Each circle represents a model. Red fitting line is the emergent constraint relationship between “simulated historical climate variable x (i.e., historical annual temperature growth rates in Fig 2)” and “predicted future climate variable y (i.e., future annual precipitation growth rates)”. Baby blue curve and gray curve are the probability density functions (PDFs) of the observed climate variable x and simulated historical climate variable x. Clearly, the observed climate variable x has less uncertainties in compared to the range of simulated values of climate variable x. Thereby, by projecting the observed climate variable x into y-axis through the emergent constraint relationship, we can obtain the more accurate future future climate variable y with less uncertainties in relative the raw models’ predictions. Dark blue curve and dark curve are the PDFs of the constrained and the unconstrained future climate variable y.

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