Why did planetary energy imbalance decline during the past decade?
The observed rate of ocean heat uptake since 2003 is less than in the preceding 10 years. Indeed, early reports suggested ocean cooling after 2003 (Lyman et al., 2006). That apparent cooling was a result of instrumental artifacts, but even after corrections the rate of heat uptake was smaller than in the prior decade (Willis et al., 2007). Observational error makes it difficult to measure heat uptake on short time scales, especially pre-Argo, but the slowdown in heat uptake since 2003 seems to be robust (Levitus et al., 2009; Lyman et al., 2010). The slowdown of ocean heat uptake, together with satellite radiation budget observations, led to a perception that Earth’s energy budget is not closed (Trenberth, 2009; Trenberth and Fasullo, 2010), as summarized in Fig. 19A. However, our calculated energy imbalance is consistent with observations (Fig. 19b), implying that there is no missing energy in recent years.
My translation. After Willis published the data showing the oceans cooling, I took him behind the woodshed and told him that he better get that fixed and quick. Trenberth embarrassed everyone with that Climategate E-mail, so we massaged his numbers to make them appear to fit the First Law.