ON THE PAUSED WARMING CONTROVERSY BASED ON IPCC AR5 AND BEYOND
ABSTRACT. On the paused warming controversy based on IPCC AR5 and beyond. The paused warming since ca. 2002 (maybe, 1998) is not satisfactorily reflected by the IPCC WGI (2013) Report. The aim of the present study is to collect, present and discuss the key arguments of the issue, selected strictly from this valuable Report. Our study tackles three aspects: (i) Symptoms of pausing, including atmospheric changes, near-surface oceans, cryosphere and geographical differences. (ii) Possible reasons of the paused warming, including external forcing factors, playing rather minor role, and the enhanced ocean heat uptake. Though missing warming is 0.2 K/decade compared to the model expectations, the whole climate system integrates continuously increasing amount of heat, 95 % of which is locked in the oceans. (iii) Consequences of the pausing for the three main branches of the IPCC activity. For climate science, correct simulation of the enhanced heat uptake is a challenge. Since characteristic time scale of most adaptation measures is 1-2 decades, or shorter, near-term projections may not drive adaptation until climate models become able meet this challenge. On the other hand, pausing warming does not question the need for mitigation, since it is physically unlikely, that oceans can uptake endless amount of heat. Vertical temperature gradients of the upper ocean layers already show stagnation.
Keywords: IPCC, geographical features, ocean heat uptake, adaptation, mitigation