Climate Change

[ewmayer]

Originally Posted by cheesehead

[Quoted from another article]
When the planet is in energy imbalance, the whole climate system accumulates heat. The atmosphere warms. Oceans accumulate energy. Land absorbs energy and ice absorbs heat to melt.
...
Figure 1 shows that the planet is accumulating heat at a rate of 190,260 GigaWatts. Considering a typical nuclear power plant has an output of 1 GigaWatt, imagine 190,000 nuclear power plants pouring their energy output directly into our oceans.

We also observe the heat capacity of the land and atmosphere are small compared to the ocean (the tiny brown sliver of "land + atmosphere" also includes the heat absorbed to melt ice). Hence, relatively small exchanges of heat between the atmosphere and ocean can cause significant changes in surface temperature.

Ok, so let's do some back-of-the-envelope-style computation:

The approximate sun-facing area of the earth is just A = pi*R^2, where R ~= 6378 km, giving A ~= 130 million km^2

Most of the radiative-balance measurements indicate an added GHG-caused forcing of ~ 2 W/m^2 = 2 MW/km^2, which translates to 260 million MW = 260,000 GW ... in line with above 190,000 GW estimate.

[It is interesting to compare this with the total (internally-generated) heat loss from the earth of 4.2 × 10^13 Watts = 42,000 GW, which means external heat flux is ~5x internal)


Next step - since earth's oceans are by far the biggest heat exchanger with the atmosphere, let's compute some plausible range of numbers for the resulting rate of change in oceanic temperatures, ignoring complications (albeit potentially important ones) such as changed evaporation/rainfall rates.

Could someone check my numbers below? Note I absolutely am not trying to make a point here ... I just want to get some basic numbers under the simplest assumptions:

----------------

Assume oceans are perfectly efficient heat sinks (this will give a lower bound on the oceanic temperature rise). Heat capacity of water ~ 4000 J/(kg*K) = 4000 W/(kg*(K/sec)), i.e. a heat input of 4000 W will raise the average temperature of a kg of water by one degree (Kelvin or Celsius) per second

Total volume of seawater in earth oceans is ~1.4 billion cubic kilometers --> mass of ~1.4*10^21 kg

If all excess heat is absorbed into oceans, 190,000 GW will cause a time-averaged temperature temperature rise rate of

[1.9*10^14 W] / [1.4*10^21 kg] / [4000 W/(kg*(K/sec))] ~= 0.3*10^-10 K/sec ~= 0.1 K/century.

Of course the oceans can only absorb a portion of the added heat (how much is a nontrivial research question) ... if e.g. only the top 100 meters (on average) of the earth's oceans were where the bulk of the heat were absorbed, since average ocean depth is 4000 m, that would result in an ocean temperature change rate ~40x the idealized one above ... but someone please confirm/deny the above computation before we proceed further.

[Fusion_power]

The risk is not so much that we humans trigger a catastrophic temperature rise, rather that we trigger a mass release of methane from deep storage which reaches a critical point and begins to trap massive amounts of heat from the sun which causes further release of methane. The resulting rise in temperature would make the equatorial region largely uninhabitable and would not subside until much of the atmospheric greenhouse gases have been reduced below the critical threshold.

DarJones

[petrw1]

Canadian Ice Breaker...

[ewmayer]

Originally Posted by Fusion_power

The risk is not so much that we humans trigger a catastrophic temperature rise, rather that we trigger a mass release of methane from deep storage which reaches a critical point and begins to trap massive amounts of heat from the sun which causes further release of methane. The resulting rise in temperature would make the equatorial region largely uninhabitable and would not subside until much of the atmospheric greenhouse gases have been reduced below the critical threshold.

Assuming for the moment that this is indeed correct ... what are the public-policy implications? Would this mean that all the attention on CO2 is misguided, or are the 2 GHGs inextricably linked? If not, is there scientific consensus on the most likely triggers for such a Methane event?

And why isn't Al Gore talking about Methane Doomsday ... does he like eating hamburgers too much to advocate drastic reductions in cows and their associated CH4-rich flatulence?

[cheesehead]

Originally Posted by Fusion_power

The risk is not so much that we humans trigger a catastrophic temperature rise, rather that we trigger a mass release of methane from deep storage which reaches a critical point and begins to trap massive amounts of heat from the sun which causes further release of methane. The resulting rise in temperature would make the equatorial region largely uninhabitable and would not subside until much of the atmospheric greenhouse gases have been reduced below the critical threshold.

I think you're mistaken in saying that "The risk is not so much that we humans trigger a catastrophic temperature rise", because that _is_ a foreseeable consequence of our current path.

We humans _are_ indeed taking the risk of foreseeably triggering a catastrophic temperature rise. Yes we are.

- - -

Originally Posted by ewmayer

Would this mean that all the attention on CO2 is misguided,

No, because CO2 is by far the most important anthropogenic greenhouse component right now, in terms of its proportional contribution to warming. Currently, and for some amount of additional warming in the near future, its vastly greater abundance in the atmosphere more than compensates for methane's larger per-molecule IR absorption.

But it is expected that eventually the CO2-dominated warming could reach a point at which the higher temperatures could begin triggering massive releases of methane into the atmosphere. And we have not yet made any progress in slowing that CO2-dominated warming.

or are the 2 GHGs inextricably linked?

All GHGs are linked in the sense that they will all cause greenhouse warming. Differences in their relative importances reflect their differing atmospheric concentrations now and in the future. Among the predicted effects of continued warming are that some now-insignificant natural sources of GHGs will become more important at higher temperatures. Warming is predicted to produce a cascade of effects, some of which will make the warming even faster.

And why isn't Al Gore talking about Methane Doomsday

Because there's still time to reduce our CO2 enough to avoid massive methane releases ... if, that is, we take action to do so. And Gore's having enough trouble getting his message across without complicating it. I'm sure he's well aware of the methane situation.

[ewmayer]

U.N. Panel’s Glacier Warning Is Criticized as Exaggerated:A much-publicized estimate from a United Nations panel about the rapid melting of Himalayan glaciers from climate change is coming under fire as a gross exaggeration.

The United Nations Intergovernmental Panel on Climate Change said in 2007 — the same year it shared the Nobel Peace Prize with former Vice President Al Gore — that it was “very likely” that Himalayan glaciers would disappear by 2035 if current warming trends continued.

That date has been much quoted and a cause for enormous consternation, since hundreds of millions of people in Asia rely on ice and snow melt from these glaciers for their water supply.

The panel, the United Nations’ scientific advisory body on climate change, ranks its conclusions using a probability scale in which “very likely” means there is greater than 90 percent chance that an event will occur.

But [i]it now appears that the estimate about Himalayan glacial melt was based on a decade-old interview of one climate scientist in a science magazine, The New Scientist, and that hard scientific evidence to support that figure is lacking[/u]. The scientist, Dr. Syed Hasnain, a glacier specialist with the government of the Indian state of Sikkim and currently a fellow at the TERI research institute in Delhi, said in an e-mail message that he was “misquoted” about the 2035 estimate in The New Scientist article. He has more recently said that his research suggests that only small glaciers could disappear entirely.

The panel, which relies on contributions from hundreds of scientists, is considering whether to amend the estimate or remove it.

“The I.P.C.C. considers this a very serious issue and we’re working very hard to set the record straight as soon as we can,” said Christopher Field, co-chairman of the panel’s section that was responsible for the report, which deals with impacts, adaptation and vulnerability.

He noted that the potentially erroneous figure in question had appeared only in the panel’s full report of more than 1,000 pages and had been omitted in later summary documents that the panel produced to guide policy.

My Comment: The latter attempt at minimization is rather laughable, given that "That date has been much quoted and a cause for enormous consternation"

Which is not to say that the glaciers are doing just dandy, but the last paragraph of the above article again features a scientist making dire and precise-sounding numerical estimates, only to conclude with an admission of uncertainty which amounts to "we really can't put any numbers on the long-term predictions". OK, so why did you?

There is mounting proof that accelerating glacial melt is occurring, although the specifics are poorly defined, in part because these glaciers are remote and poorly studied.

At an international conference last year on Asia’s glaciers, held at the University of California, San Diego, Yao Tandong, a Chinese glaciologist who specializes in the Tibetan Plateau, said, “Studies indicate that by 2030 another 30 percent will disappear; by 2050, 40 percent; and by the end of the century 70 percent.” He added: “Actually we don’t know much about process and impacts of the disappearance. That’s why we need an international effort.”

[cheesehead]

Originally Posted by ewmayer

My Comment: The latter attempt at minimization is rather laughable,

What about your attempt at minimization by failing to quote some relevant explanation that, in the article, immediately followed the sentence you quoted.

The full paragraph, as it appears in the article, is:

Originally Posted by http://www.nytimes.com/

He noted that the potentially erroneous figure in question had appeared only in the panel’s full report of more than 1,000 pages and had been omitted in later summary documents that the panel produced to guide policy. The summaries said only that the Himalayan glaciers “could decay at very rapid rates” if warming continued. Such documents are produced after panel members review a full-length report, although if a figure in the report is deemed to be in error, it is supposed to be removed.

Inclusion of the latter two sentences in your quote might have given an impression of more reasonableness.

Originally Posted by ewmayer

the last paragraph of the above article again features a scientist making dire and precise-sounding numerical estimates,

Really? You think it's all right to make that characterization on the basis on just two sentences quoted out of context? Do you know for certain that the full context of what that scientist ("Yao Tandong, a Chinese glaciologist who specializes in the Tibetan Plateau") said omits error estimates, for instance?

Of course, including error estimates might make that Yao's statements seem less "dire and precise-sounding". So I don't blame you for not hunting down and quoting a fuller context, since that could only reduce the emotional impact of your insinuations.

- - -

BTW, here's the Nature News article on the glacier estimate mistake: http://www.nature.com/news/2010/1001...l/463276a.html

It explains that there was apparently some human error in following the procedure for using non-refereed studies while writing the report.

[Murari Lal, director of the Climate, Energy and Sustainable Development Analysis Centre in Ghaziabad, who served as coordinating lead author for the Asia chapter in the working group report] says that his team followed proper IPCC procedures for using non-refereed studies, which require chapter teams to review the quality of such sources before citing results. The WWF report seemed credible, he says, but he admits that the team should have looked more carefully at the secondary sources to which it refers.

. . .

The section also includes other, smaller errors that are drawing less attention.

. . .

But the summary findings are not in question:

IPCC representatives say that the bottom line of the Asia chapter remains the same. "There is no scientific doubt on the rapid melting of the glaciers in the Himalayas," says Pachauri, although they are very unlikely to disappear during the next few decades.

The IPCC has issued an apology: http://www.ipcc.ch/pdf/presentations...anuary2010.pdf
and there's a Nature blog entry commenting on the apology: http://blogs.nature.com/news/thegrea...himalayan.html

- - -

I continue to eagerly await the AGW-deniers' presentation of a hypothesis that explains the observed data as well as, or better than, the AGW hypothesis, without attributing significant effect to anthropogenic greenhouse gases.

[xilman]

Originally Posted by xilman

Ernst, please bear with me for I am only a simple chemist and have a simple question based on my imperfect and decades old classes in thermodynamics.

I think we both accept, from Evans if nothing else, that radiative absorption has increased by a reasonably well characterised amount. That is, the planet as a whole is acquiring heat somewhat more rapidly than it did, say, three hundred years ago.

When I add heat to a system, at least one of (at least) four things tend to occur.

First, it may increase in temperature. In the present case, this would be AGW.

Second, it may radiate more heat. We're considering the entire planet as "the system", so the amount of heat lost by convection and conduction to the interplanetary medium may be regarded as negligible.

Third, an isothermal physical phase change may take place. The latent heat of the phase change absorbs the added energy without any rise in temperature. For example, melting ice remains at (essentially) zero Celsius; a process which appears to be occurring at many places around the world.

Fourth, an endothermic chemical or mechanical reaction may occur. For example, the energy might go into convection currents such as storms or oceanic currents.


My question: what am I missing? If anthropogenic increased radiative absorption is an accepted phenomenon, where is that energy going if not into raising temperatures, melting ice and driving weather systems and oceanic currents?


Paul

Ernst, I posted this a month ago but haven't seen a response. Now that's no problem because I knew your posting activity would be disrupted by your going on vacation and by the Xmas / New Year activities.

However, I would like to read your thoughts on the matter because I believe the question probes an important component of the whole matter of GW.


Thanks,

Paul

[ewmayer]

Originally Posted by xilman

Ernst, I posted this a month ago but haven't seen a response. Now that's no problem because I knew your posting activity would be disrupted by your going on vacation and by the Xmas / New Year activities.

However, I would like to read your thoughts on the matter because I believe the question probes an important component of the whole matter of GW.


Thanks,

Paul

Ah, yes, thanks for the reminder-poke, Paul.

Briefly: In the short run, absent any violently nonlinear countereffects or the system having been extremely close to some kind of tipping point to begin with (both of which appear to be reasonable assumptions based on trends of the past century), indeed, to first order one expects response to follow forcing, i.e. to see a quasi-linear local response. In this case, more lower-stratosphere radiation absorption means a warmer troposphere.

Extrapolating those trends to larger and/or longer-term forcing - where nonlinearity, complex interactions and time lags of various disparate components of the climate system do matter greatly - is where things get tricky, and this is where numerical modeling is really our only viable option, and as I have noted, that`s where the "scientific consensus" argument falls apart, because the uncertainty of the modeling is far, far larger than the folks at the IPCC care to admit. To claim that "the models agree" even with respect to the sign of the expected changes 50-100 years out is just plain bad science.

[storm5510]

Why cannot anyone speak of this in practical terms?

All I can say is that something is different with the environment. I had never heard of severe thunderstorms in L.A. until recently; large hail, damaging winds, tornado's.

Where I live, this time of the year is normally the coldest. Not this time. 50°F, or higher, for nearly a week.

It's not just in a few places, it's a lot of places seeing conditions radically different than what is/was considered normal.

Those who claim there is not a problem do not want to see the problem...

[Uncwilly]

Originally Posted by storm5510

All I can say is that something is different with the environment. I had never heard of severe thunderstorms in L.A. until recently; large hail, damaging winds, tornado's.

You may want to educate yourself. Here are few links to help you out.
Infamous New Year’s Day Flood, Los Angeles Basin, 1934
Freak Storm Leaves Los Angeles Under a Foot of Hail
1938 Severe flooding claims 78 lives and causes almost $25 million in damage. 1941, 1942, 1943, 1944 The Los Angeles River overflows and causes floods.
March 1983 Tornado damages the Los Angeles Convention Center
Years with multiple tropical cyclones that have affected Southern California this century

People have short memories.

Great Lakes Blizzard of 1977