Figure 1
Schematic illustration of the challenge encountered when defining the climate shifting velocity field in regions where curved isotherms shift northwards. We consider the displacement of isotherm T from time t to time \(t+\text {d}t\) (blue lines). (a) Gradient-based velocity. The shifting (red arrows) occurs along the gradient, i.e., perpendicular to the isotherms. The velocity field exhibits shear and artificial convergence, particularly marked in the case of the dashed arrows, that furthermore do not reach the isotherm of time \(t + \text {d}t\). (b) Velocity field minimizing the displacement. Shear, and local bunching and loosening is also unavoidable in curved regions of the isotherms. (c) MATCH approach, yielding a velocity field as uniform and as little sheared as possible.
