Reducing Uncertainty in Climate Projections for the Mid and High Latitudes of the Northern Hemisphere

Abstract

The mid latitudes and high latitudes of the Northern Hemisphere are warming faster than the global average, particularly over land. Model uncertainty in the forced response is the largest contributor to the total uncertainty in climate projections for these regions. Beyond climate sensitivity differences, regional climate feedbacks—like Arctic sea-ice loss—drive model uncertainty of the climate response. By applying emergent constraints based on the observed global warming trend and a metric related to Arctic sea ice loss, we reduce uncertainty in projected air temperature and precipitation changes over high-latitude land areas. Based on an imperfect model test, such projections outperform projections constrained using only the global warming trend or unconstrained projections. Compared to unconstrained projections, our approach reduces uncertainty by 22%–47% for temperature changes and 10%–51% for precipitation changes across different IPCC regions in the mid to high latitudes of the Northern Hemisphere by the end of the century under a middle-of-the-road scenario.