Quantifying underestimates of long-term upper-ocean warming

NATURE CLIMATE CHANGE

Ocean Warming has been Greatly Underestimated

Posted on 14 October 2014 by Rob Painting

Key Points:

• The oceans are by far the largest heat reservoir on Earth, absorbing 93% of global warming. Because of this, accurate assessments of heat uptake are essential to balance the sea level budget, and for observationally-based estimates of climate sensitivity.     

• Prior to 2005, when the Argo global array of submersible floats became operational, ocean temperature was much more sparsely sampled, especially in the southern hemisphere, leading to larger uncertainty over the evolution of ocean warming through time.

• Durack et al (2014) analyse the period from 1970-2004 combining ocean temperature and sea surface height measurements with climate model simulations, and find that sparse sampling in the southern hemisphere oceans, and limitations of previous analytical methods, has led to a substantial underestimate of warming in the 0-700 metre layer*.

• When corrected for this bias, Durack (2014) find that the top 700 metre layer of ocean, over the period 1970-2004, has warmed some 24-58% more than previous analyses have indicated. 

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Original Article