Is Global Heat Uptake Accelerating – Or Not?

Hansen &al’s claim – an increase in global net heat uptake resultung in a warming rate increase from 0.18 to 0.27 K/decade – is absolutely alarming, catastrophic. But it has been critized by other eminent climate scientists, e.g. Michael Mann here. I had some discussion about it on twitter. I see 2 problematic points in Hansen &al (there are other points, but those are i.m.o. the most important) :

• radiative power balance. Hansen takes Loeb &al’s CERES result at face value, which are as clear as it can get: the globe absorbs more power with every decade. the earth albedo is decreasing. The critics say, they have not that much trust here, as power balance measurements are extremely difficult: you have to subtract two values (integral incoming & outgoing radiation) whith the relative difference being ~10^-3. So a relative sensor drift of 10^-3 in 2 decades would already skew the result.
• ocean heat content. the elegant thing with Hansen &al’s paper is, that a meticulous summation of the earths heat content anomaly – which is basically the ocean heat content anomaly – leads to an increase in net absorbed power which fits nicely to the value got by CERES. They get the same net absorbed power increase by two independent methods – a scientists dream. Here data from von Schuckmann &al are used. Problem is, reconstructing the oceanic temperature field from some measurement points and a lot of reananlysis is an even more daunting task than reconstructing the surface temperature field. keyword here: systematic errors changing over time. Mann uses a different ocean heat content reconstruction by Cheng &al which – tadaa – shows no acceleration in heat uptake and which he claims is done better.

So as bystanders, we are left alone with the hands up in the air. The matters discussed are so intricate, demand so much detailed knowledge, that we laymen really have to wait for them to be settled in the scientific discussion, which may take quite some time.

The practical problem we are facing is simpler but at least as difficult to solve: convince the majority, that a) a sense of real urgency is the thing to have and b) successful action is possible for everybody and worth the effort.