Trends in the Earth's Energy Imbalance

 

A study was published last year that used two independent methods to estimate the rate at which the Earth's Energy Imbalance is increasing between mid-2005 and mid-2019. The first method used in situ measurements to calculate the planetary heat uptake. This method found the trend for 0–2,000 m ocean heat content anomaly to be 0.43 ± 0.40 W/m^2/decade. The second method used satellite measurements to calculate a CERES TOA energy flux of 0.50 ± 0.47 W/m^2/decade. These two trends were statistically identical to each other - the difference between them was 0.068 ± 0.29 W/m^2/decade. 

The average value for EEI for the entire study period was 0.77 ± 0.06 W/m^2. In a previous post, I used three different estimates for EEI, this paper, one from Hansen (2005-2010) and one from von Schuckmann (2011-2018). I plotted all three of these values in the center year for the estimate in yellow as "studies."  In the above graph, I plotted the values for CERES and in situ measurements as dotted lines and the average of the two as a black line with a trendline. The three estimates fall roughly on that line. It seems to me we have a pretty good estimate of how much more energy is entering the climate system than is escaping into space. Calculating sensitivity from Loeb's study requires us to average the ΔFc for 2005 to 2019 (the dates used in the study).[1]  However, we also need to correct for the fact that increases in CO2 forcings (ΔFc) have totaled 2.11 W/m^2 while total forcings (ΔFt) including other GHGs and aerosols have been 2.17 W/m^2. In other words, CO2 forcings have been responsible for about 97% of the total increase in radiative forcing (ΔFt), such that ΔFc = 0.9724 x ΔFt. Making this adjustment, the increase in radiative forcing, this this is what we get:

2005 - 2019 (Loeb)
ΔFc = 1.838 W/m^2

ΔFt = 1.890 W/m^2
EEI = 0.77 W/m^2[1]
ΔT = 0.991 C
λ = 0.885 C/W/m^2

ECS = 3.28 C

This result is predictably right in line with my previous results. The Loeb study, however, does point out that not all of this trend is due to climate forcings from greenhouse gases. The PDO (whatever that turns out to be) shifted to its positive phase in 2014, and this was followed by an El Nino year beginning in 2015. So internal variability accounts for some of the upward trend in EEI here, which is good news. I don't like the idea of the earth's energy imbalance increasing by 0.5 W/m^2 every decade.

Reference:

[1] Loeb, N. G., Johnson, G. C., Thorsen, T. J., Lyman, J. M., Rose, F. G., & Kato, S. (2021). Satellite and ocean data reveal marked increase in Earth’s heating rate. Geophysical Research Letters, 48, e2021GL093047. https://doi.org/10.1029/2021GL093047