A reappraisal of the messy data on upper-ocean heat content for 1993–2008 provides clear evidence for warming. But differences among various analyses and inconsistencies with other indicators merit attention. The upper ocean acts as a giant heat sink and has absorbed the majority of excess energy generated by anthropogenic greenhouse gasses. This makes ocean heat content, potentially, a key indicator of climate change. But to be useful for evaluating the global energy balance and as a constraint on climate models, the measurement uncertainties of such a key indicator need to be well understood. At present the magnitude of the oceanic heat uptake is highly uncertain, with patterns of inter-annual variability in particular differing among estimates. In a major international collaboration, Lyman et al. compare the available upper-ocean heat content anomaly curves and examine the sources of uncertainly attached to them — including the difficulties in correcting bias in expendable bathythermograph data. They find that, uncertainties notwithstanding, there is clear and robust evidence for a warming trend of 0.64 watts per square metre between 1993 and 2008.
Lijing Cheng, Karina von Schuckmann, John Abraham, Kevin E Trenberth, Michael Mann, Laure Zanna, Matthew H. England, Jan D. Zika, John Fasullo, Yongqiang Yu, Yuying Pan, Jiang Zhu, Emily R. Newsom, Ben Bronselaer, Xiaopei Lin
Discussion(0)
No comments yet. Be the first to comment.