What ocean heating reveals about global warming

[ScienceRocks]

What ocean heating reveals about global warming

RealClimate: What ocean heating reveals about global warming

The heat content of the oceans is growing and growing. That means that the greenhouse effect has not taken a pause and the cold sun is not noticeably slowing global warming.

NOAA posts regularly updated measurements of the amount of heat stored in the bulk of the oceans. For the upper 2000 m (deeper than that not much happens) it looks like this:

The amount of heat stored in the oceans is one of the most important diagnostics for global warming, because about 90% of the additional heat is stored there (you can read more about this in the last IPCC report from 2007). The atmosphere stores only about 2% because of its small heat capacity. The surface (including the continental ice masses) can only absorb heat slowly because it is a poor heat conductor. Thus, heat absorbed by the oceans accounts for almost all of the planet’s radiative imbalance.

If the oceans are warming up, this implies that the Earth must absorb more solar energy than it emits longwave radiation into space. This is the only possible heat source. That’s simply the first law of thermodynamics, conservation of energy. This conservation law is why physicists are so interested in looking at the energy balance of anything. Because we understand the energy balance of our Earth, we also know that global warming is caused by greenhouse gases – which have caused the largest imbalance in the radiative energy budget over the last century.

 

[ScienceRocks]

Slowdown in the upper ocean

Let us look at the upper ocean (for historic reasons defined as the upper 700 m):

Change in the heat content of the upper 700 m of the oceans. Source: NOAA



And here is the direct comparison since 1980:

Changes in the heat content of the oceans. Source: Abraham et al., 2013. The 2-sigma uncertainty for 1980 is 2 x 1022 J and for recent years 0.5 x 1022 J



We see two very interesting things.

First: Roughly two thirds of the warming since 1980 occurred in the upper ocean. The heat content of the upper layer has gone up twice as much as in the lower layer (700 – 2000 m). The average temperature of the upper layer has increased more than three times as much as the lower (because the upper layer is only 700 m thick, and the lower one 1300 m). That is not surprising, as after all the ocean is heated from above and it takes time for the heat to penetrate deeper.

Second: In the last ten years the upper layer has warmed more slowly than before. In spite of this the temperature still is changing as rapidly there as in the lower layer. This recent slower warming in the upper ocean is closely related to the slower warming of the global surface temperature, because the temperature of the overlaying atmosphere is strongly coupled to the temperature of the ocean surface.

That the heat absorption of the ocean as a whole (at least to 2000 m) has not significantly slowed makes it clear that the reduced warming of the upper layer is not (at least not much) due to decreasing heating from above, but rather mostly due to greater heat loss to lower down: through the 700 m level, from the upper to the lower layer. (The transition from solar maximum to solar minimum probably also contributed a small part as planetary heat absorption decreased by about 15%, Abraham, et al., 2013). It is difficult to establish the exact mechanism for this stronger heat flux to deeper water, given the diverse internal variability in the oceans.

 

[Abraham3]

It is difficult to establish the exact mechanism for this stronger heat flux to deeper water, given the diverse internal variability in the oceans.

Thanks for all this Matthew.

The concluding line, quoted above, is where our 'friends' on the other side are going to attack you. The answer is suggested in the conclusion of Balmaseda, Trenberth and Kallen's 2013: Distinctive climate signals in reanalysis of global ocean heat content:

4. Summary and Conclusions

[15] The time evolution of the global OHC for the period 1958–2009, as estimated by the ORAS4 ocean reanalysis, is dominated by a warming trend and pronounced cooling episodes, and shows an increasing warming trend at depths below 700 m. The cooling episodes correspond to cooling seen in SSTs in response to the El Chichón and Mt Pinatubo eruptions, and the radiative imbalance associated with the latter [Trenberth and Dai, 2007] is consistent with the cooling found here. More surprising is the extra cooling following 1998, a likely consequence of the ocean heat discharge associated with the massive 1997–1998 El Niño event [Trenberth et al., 2002]. Meehl et al. [2011] have demonstrated in a model study how La Niña events and negative PDO events could cause a hiatus in warming of the top 300 m while sequestering heat at deeper layers. This mechanism can also explain the increasing role of the depths below 700 m after 1999 in the ORAS4 OHC, consistent with La Niña-like conditions and a negative phase of the PDO which has dominated the last decade. The deep ocean warming, which mostly involves the depth range 700–2000 m, may also be related to the weakening of the MOC after 1995, which is present in ORAS4 [BMW13]. Possibly changes in MOC and PDO are connected through changes in the atmospheric circulation patterns.[16] The deep ocean has continued to warm, while the upper 300 m OHC appears to have stabilized. The differences in recent trends among the different ocean layers are profound. The small warming in the upper 300 m is belied by the continuing warming for the ocean as a whole, with considerable warming occurring below 700 m. However, this raises the question of whether this result is simply because of the new Argo observing system? The results shown here suggest otherwise, although Argo clearly is vitally important quantitatively. Instead changes in surface winds play a major role, and although the exact nature of the wind influence still needs to be understood, the changes are consistent with the intensification of the trades in subtropical gyres. Another supporting factor is the uniqueness of the radiative forcing associated with global warming. [17] The magnitude of the warming trend is consistent with observational estimates, being equivalent to an average 0.470.03 W m–2 for the period 1975–2009. There is large decadal variability in the heat uptake, the latest decade being significantly higher (1.190.11 W m–2 ) than the preceding record. Globally this corresponds to 0.84 W m–2 , consistent with earlier estimates [Trenberth et al., 2009]. In an observing system experiment where Argo is withdrawn, the ocean heating for the last decade is reduced (0.820.10 W m–2), but is still significantly higher than in previous decades. The estimation shows depths below 700 m becoming much more strongly involved in the heat uptake after 1998, and subsequently accounting for about 30% of the ocean warming. [18] The analysis of ORAS4 OHC shows some interesting signals. In particular, the prolonged and intense cooling events during the 1980s and 1990s are not as distinct in other observation-only analyses [BMW13], and the rapid involvement of the deep ocean starting around the 1998–1999 La Niña needs further investigation. Sensitivity experiments indicate that these features are robust, and suggest that changes in the atmospheric circulation play an important role in the heat uptake. Detecting, understanding and modeling the processes that lead to the vertical distribution of heat within the ocean is a key for the correct initialization of decadal predictions, because the trends in forecasts of the SST will likely depend on whether the ocean is in a recharge (low stratification) or discharge (high stratification) mode.

http://www.cgd.ucar.edu/cas/Trenber...s-moved/Balmaseda_Trenberth_Kallen_grl_13.pdf

So, the combination of a la Nina and a negative PDO seems to cause changes to the subtropical gyres that result in a slowdown in warming in the upper layers of the ocean and a simultaeous sequestration of heat in the lower layers.

But let's be open-minded here. Westwall, Daveman, FlaCalTenn, C. Frank, skookerasnoc, American Jihad - do you have alternative explanations for the observations?

 

[skookerasbil]

nobody cares

 

[PMZ]

When OLR is effectively reduced in radiating out of the earth system, and incoming solar radiation is effectively constant, there is no alternative to earth's surface warming until energy balance is restored. The thermodynamic process that achieves that is impossibly complex and slow in occurring. Just the atmospheric part is what we call weather, and the land and life and oceans and ice and snow are all equally involved. Impossible to predict over the long term.

So, the best that we can do, given that AGW is unprecedented in earth's history, is to gather an immense amount of data from all of those systems over time, and look for clues as to how it happens.

Exactly as we're doing.

 

[tinydancer]

Psssst, there's been no warming since 1998.

Give it up.

 

[mamooth]

The point, kooks (that's you, skook and tinydancer), is how it requires someone pretend that the oceans don't exist in order to claim something as stupid as "there's been no warming since 1998!". Those who are not sputtering 'tards understand that the oceans are part of planet earth.

It's not a difficult concept. Are you two simply too dumb to understand the basics, or are you deliberately lying for the glory of your cult?

 

[PMZ]

The point, kooks (that's you, skook and tinydancer), is how it requires someone pretend that the oceans don't exist in order to claim something as stupid as "there's been no warming since 1998!". Those who are not sputtering 'tards understand that the oceans are part of planet earth.

It's not a difficult concept. Are you two simply too dumb to understand the basics, or are you deliberately lying for the glory of your cult?

Conservatives have been promised by their cult leaders that if you wish hard enough, hard enough to the point of lying, what you want will come true.

They are completely unable to see what falling for that says about them.

 

[flacaltenn]

Slowdown in the upper ocean

Let us look at the upper ocean (for historic reasons defined as the upper 700 m):

Change in the heat content of the upper 700 m of the oceans. Source: NOAA



And here is the direct comparison since 1980:

Changes in the heat content of the oceans. Source: Abraham et al., 2013. The 2-sigma uncertainty for 1980 is 2 x 1022 J and for recent years 0.5 x 1022 J



We see two very interesting things.

First: Roughly two thirds of the warming since 1980 occurred in the upper ocean. The heat content of the upper layer has gone up twice as much as in the lower layer (700 – 2000 m). The average temperature of the upper layer has increased more than three times as much as the lower (because the upper layer is only 700 m thick, and the lower one 1300 m). That is not surprising, as after all the ocean is heated from above and it takes time for the heat to penetrate deeper.

Second: In the last ten years the upper layer has warmed more slowly than before. In spite of this the temperature still is changing as rapidly there as in the lower layer. This recent slower warming in the upper ocean is closely related to the slower warming of the global surface temperature, because the temperature of the overlaying atmosphere is strongly coupled to the temperature of the ocean surface.

That the heat absorption of the ocean as a whole (at least to 2000 m) has not significantly slowed makes it clear that the reduced warming of the upper layer is not (at least not much) due to decreasing heating from above, but rather mostly due to greater heat loss to lower down: through the 700 m level, from the upper to the lower layer. (The transition from solar maximum to solar minimum probably also contributed a small part as planetary heat absorption decreased by about 15%, Abraham, et al., 2013). It is difficult to establish the exact mechanism for this stronger heat flux to deeper water, given the diverse internal variability in the oceans.

You realize Matthew -- As Abraham just pointed out.. That NOAA is at odds with that famous Trenberth dude as to WHERE the heating is occuring... But they are CERTAINLY CLEAR that there's HEATING somewhere..

10tothe 22nd power might SEEM like a big number -- but it's really not considering the scale of the ocean volume involved.. I'm thinking SOMEONE needs to publish a REAL PAPER so we can all see how those TEMPERATURES were CONVERTED to joules and WHERE the historic data came from..

Before we all go off blathering.. Never seen a Chinese Fire Drill quite like this circus playing out in front of the public...

 

[Abraham3]

You realize Matthew -- As Abraham just pointed out.. That NOAA is at odds with that famous Trenberth dude as to WHERE the heating is occuring... But they are CERTAINLY CLEAR that there's HEATING somewhere..

Can you not read or do you just choose not to? Balmseda was the lead on that study. Balmaseda and NOAA agree.

 

[PMZ]

Slowdown in the upper ocean

Let us look at the upper ocean (for historic reasons defined as the upper 700 m):

Change in the heat content of the upper 700 m of the oceans. Source: NOAA



And here is the direct comparison since 1980:

Changes in the heat content of the oceans. Source: Abraham et al., 2013. The 2-sigma uncertainty for 1980 is 2 x 1022 J and for recent years 0.5 x 1022 J



We see two very interesting things.

First: Roughly two thirds of the warming since 1980 occurred in the upper ocean. The heat content of the upper layer has gone up twice as much as in the lower layer (700 – 2000 m). The average temperature of the upper layer has increased more than three times as much as the lower (because the upper layer is only 700 m thick, and the lower one 1300 m). That is not surprising, as after all the ocean is heated from above and it takes time for the heat to penetrate deeper.

Second: In the last ten years the upper layer has warmed more slowly than before. In spite of this the temperature still is changing as rapidly there as in the lower layer. This recent slower warming in the upper ocean is closely related to the slower warming of the global surface temperature, because the temperature of the overlaying atmosphere is strongly coupled to the temperature of the ocean surface.

That the heat absorption of the ocean as a whole (at least to 2000 m) has not significantly slowed makes it clear that the reduced warming of the upper layer is not (at least not much) due to decreasing heating from above, but rather mostly due to greater heat loss to lower down: through the 700 m level, from the upper to the lower layer. (The transition from solar maximum to solar minimum probably also contributed a small part as planetary heat absorption decreased by about 15%, Abraham, et al., 2013). It is difficult to establish the exact mechanism for this stronger heat flux to deeper water, given the diverse internal variability in the oceans.

You realize Matthew -- As Abraham just pointed out.. That NOAA is at odds with that famous Trenberth dude as to WHERE the heating is occuring... But they are CERTAINLY CLEAR that there's HEATING somewhere..

10tothe 22nd power might SEEM like a big number -- but it's really not considering the scale of the ocean volume involved.. I'm thinking SOMEONE needs to publish a REAL PAPER so we can all see how those TEMPERATURES were CONVERTED to joules and WHERE the historic data came from..

Before we all go off blathering.. Never seen a Chinese Fire Drill quite like this circus playing out in front of the public...

Where's your evidence?

 

[PMZ]

The inconvenient truth that all conservative posts have to avoid is that AGW is a scientific certainty. It is happening and will keep increasing for at least 100 years, probably longer. That’s simple reality, no matter how inconvenient.

That's the foundation for all of these discussions. That needs to be the underlying assumption for all of these posts and threads.