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Estimates of ocean warming have been revised substantially upward – by around 40% – in the years since the IPCC 5th Assessment Report, as we discuss in our article in Science today (w/ @Lijing_Cheng). Over at @CarbonBrief we provide a detailed look: carbonbrief.org/guest-post-obs… [1/6] 
Around 93% of the additional heat trapped by greenhouse gases in the atmosphere ends up being absorbed by the oceans. Ocean heat content is a critical measure of climate change, and shows the warming signal much more clearly than the more noisy surface record. [2/6]
Four groups have published new or revised ocean heat content estimates in recent years. These benefit from better corrections to biases in expendable bathythermograph measurements and more sophisticated approaches for dealing with data gaps, or apply novel approaches. [3/6]
These recent observational estimates also tend to agree quite well with climate model projections (at least the CMIP5 mean; not all individual models get it right), and resolve what was a worrying discrepancy between models and the OHC observations featured in the IPCC AR5: [4/6]
Observations also are broadly consistent with models over the more-recent Argo period (post-2005) when the observational uncertainty is much smaller due to a vast improvement in the number and quality of observations: [5/6]
We can now say with confidence now that 2018 will be the warmest year on record for the Earth's oceans, beating the second-place year (2017) by a comfortable margin. [6/6]
Our perspective in Science can be found here: doi.org/10.1126/scienc…, by @Lijing_Cheng, John Abraham, Kevin Trenberth, and myself. My first time publishing in Science, which is exciting!
(Or will be available at that link shortly once its up on their website...)
