Auditing the Earth's sea-level and energy budgets

Nov 04, 2011

An international research team has balanced the sea-level rise budget by showing that the total amount of contributions to sea level rise explains the measured rise over recent decades.

Scientists have accounted for all the contributions to global sea-level in a study that balances the sea-level rise ‘budget’ and explains the observed rise over recent decades.

In work led by CSIRO Wealth from Oceans Flagship Drs John Church and Neil White and published in mid-September in the American Geophysical Union’s Geophysical Research Letters, the researchers also reviewed the related Earth’s energy budget – confirming that 90% of the energy stored in the climate system resides in the ocean and this warming drives one component of sea-level rise.

The international research team found that the two largest contributions to observed sea-level rise since 1972 came from ocean thermal expansion (about 40%) and glacier melting (another 35%). The remainder is from changes in the ice sheets and terrestrial storage in reservoirs and extraction of groundwater from aquifers.

The new research resolves an issue evident in past IPCC Assessments in which the actual observed rise over recent decades was larger than the sum of contributions to sea-level rise, raising concern that the IPCC may have underestimated future rise.

“There are many factors contributing to sea-level rise, including changing groundwater storage, thermal expansion of the oceans, and melting glaciers and ice sheets,” says Dr Church.

“Closing the sea-level budget required accurate estimates of ocean warming, by far the largest storage of heat in the Earth’s climate system

“The sum of contributions has been less than the observed rise. To resolve this, we revisited the Earth’s sea-level and energy budgets together using new and updated estimates of all contributing factors for the past few decades, and including a new estimate of groundwater depletion. This allowed us to balance the sea-level budget from 1972 to the present,” Dr Church said.

He said that and ocean warming had continued to increase up to the present time, in concert with increasing greenhouse gas concentrations. However, aerosols have the potential to partially mask the effects on global temperature of balancing the Earth’s energy .  An increase in aerosol emissions, probably from developing countries, and moderate volcanic activity are inferred from the result.

Explore further: Sea-level surge at Antarctica linked to icesheet loss

More information: Geophysical Research Letters, doi:10.1029/2011GL048794

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GSwift7
2 / 5 (8) Nov 04, 2011
However, aerosols have the potential to partially mask the effects on global temperature of balancing the Earths energy budget. An increase in aerosol emissions, probably from developing countries, and moderate volcanic activity are inferred from the result


Sorry, but that is obviously not a valid theory. Keeping in mind that northern and southern hemispheres do not mix well, and that most of the aerosols in question are in the north, then the cooling should be in the north. It hasn't been. To the contrary, the Northern hemisphere and specifically the regions with the most aerosols, have seen continued and more severe warming.

There must be some other explanation than aerosols. These people need to check the literature. This has been talked about quite a lot lately, and most prominent experts have dismissed the aerosol masking.
GSwift7
2.1 / 5 (7) Nov 04, 2011
To my knowledge, the best idea so far is Kevin Trenberth's idea that ocean mixing is much more efficient than we have previously assumed.

Of course that is a double edged sword, because if the ocean can slow a decade of warming then it can also artificially amplify a dacade of warming. It creates as many questions as it does answers, in regard to century scale trends, if it is the true answer.

Of course this idea isn't universally accepted by the experts either. I believe Mike Mann is one who doesn't agree. I think he simply favors the idea that a decade of stalled warming is totally to be expected and that it will happen every so often, despite a longer scale trend in warming.
antialias_physorg
5 / 5 (1) Nov 04, 2011
To the contrary, the Northern hemisphere and specifically the regions with the most aerosols, have seen continued and more severe warming.

Only if aerosols are the only factor. Maybe they are a mitigating factor and the warming would be even more sever if they were not present? Just saying that you can't dismiss this on the grounds of a mono-causal argument.
GSwift7
2.3 / 5 (6) Nov 04, 2011
to antialias:

Well, I'll leave that up to the experts. I was just pointing out that there has been a lot of discussion about this amongst the top experts recently, and the idea that aerosols are the cause of the warming pause isn't a popular one. There are papers about it. If you check RealClimate, I think you'll find discussions there about why the aerosols aren't a good fit to the observations.
Pirouette
1 / 5 (2) Nov 04, 2011
And don't forget the article from the other day on Physorg concerning the jellyfish and other marine life that somehow mix warmer water with cold and the result is warmer seas.
Howhot
1 / 5 (3) Nov 05, 2011
There are many factors contributing to sea-level rise, including changing groundwater storage, thermal expansion of the oceans, and melting glaciers and ice sheets


Basically all effects of massive global warming from greenhouse gas build up.

Nuff said.

GSwift7
1.7 / 5 (6) Nov 07, 2011
Basically all effects of massive global warming from greenhouse gas build up.


How does ground water use have anything to do with GHG's?

Nuff said.
Doom1974
1 / 5 (1) Nov 07, 2011
[i] Basically all effects of massive global warming from greenhouse gas build up. How does ground water use have anything to do with GHG's? [/i]

Ummm...extra sea level rise due to water shifting to the oceans instead the aquifers....
GSwift7
1 / 5 (1) Nov 08, 2011
Ummm...extra sea level rise due to water shifting to the oceans instead the aquifers


That is an inconsequential, probably too small to measure, effect, and it has nothing to do with greenhouse gasses. The main effect of ground water depletion is called land subsidence. Areas where ground water is depleted will sink. The same thing happens when oil and natural gas are harvested, but that isn't as widespread or high volume. Places like Boston are seeing the damaging effects of this as the land falls relative to sea level, and salt water intrudes into the vacant aquifers once the fresh water is pumped out. New York doesn't see much of this problem because Manhattan sits mostly on bedrock and they do not have ground water there to pump out (not much anyway).

Besides, the amount of ground water we have pumped up is likely dwarfed by the amount of water we are storing in reservoirs and behind dams.