Sunday, July 31, 2016

Ocean Heat Content Declines Significantly With the Large El Nino

Ocean heat content numbers are out for the 2nd quarter of 2016, and they show big drops from a year ago, due to all the heat released in the recent large El Nino.

The 0-700 meter OHC change was down 1.68 W/m2 from a year ago, and the 0-2000 m OHC change was down 1.51 W/m2.

The acceleration for the 0-2000 m region -- the top half of the global ocean -- is now [WARNING: numerology] down to 0.01 ± 0.03 W/m2, which is OK since about 10-20 years of data is necessary to reliably detect an acceleration, according to Wouters et al 2013.

Here's the history of 12-month changes in the 0-700 m OHC (the 0-2000 m OHC was reliably measured only beginning in 1Q2005):

I didn't mention this because it was widely reported elsewhere, but Cheng et al (including Kevin Trenberth and John Abraham) recently published a value for all-ocean all-depth OHC changes of 0.46 W/m2 from 1971-2005 and 0.77 W/m2 from 1992-2005.

No, this doesn't mean the end of global warming.

As ATTP writes, these numbers are in good agreement with the ensemble median of climate models:

especially when you consider the error bars, which I did not include above.

Climate models certainly don't predict everything accurately -- predictions are impossible anyway, except in hindsight -- but getting the energy imbalance right is probably the most important result of all.


Anonymous said...

The El Nino, according to ONI, started in FMA 2015 and peaked in NDJ of 15-16. During this time both the GMST anomalies and the OHC anomalies went up. It is not until GMST anomalies start dropping as the El Nino weakened that this drop in OHC occurs. So am I wrong to think some of the loss in 0 to 2000 meter OHC was to the deeper ocean and not just to the atmosphere?

Roger said...

Very good post. You give OHC values as a flux ( in Watts m-2 ), however. Please clarify.

David Appell said...

Roger, it's a standard calculation.

If J Joules go into the ocean over a time T, then the average heat flux into the ocean is

J/T/area of Earth.

I use the area of the Earth because the vast majority of the trapped heat, ~93%, goes into the ocean.

Roger said...

David - You wrote

"The 0-700 meter OHC was down 1.68 W/m2 from a year ago, and the 0-2000 m OHC was down 1.51 W/m2."

OHC is in units of Joules. That was my comment. You should wordsmith.

Roger Sr

David Appell said...

Roger: Same response.

IF OHC decreases by J Joules in a time T, then its average rate of decrease is


which has units of Watts per square-meter.

Roger said...

Then you should write "the 0-700 meter RATE of change of OHC...." I know what you meant but others might be confused by your shorthand.

Roger said...

P.S. "Change" is not the same as "flux" which is the rate of change. At least that is how I use the terms. :-) Not a major issue - I have the same type of comment when writers use "resolution" in a model when they really mean "grid increment". Roger Sr

David Appell said...

Roger, good point, thanks. I changed it to "OHC change...."

David Appell said...

I realize change and flux are different. But "flux" is one of those scientists words that popular readers might not understand. I'm going to stick with change.

THanks for commenting.