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How much warmer on Earth in 2100, compared to mid-19th century?

1-2 degrees
4 (4%)
2-3 degrees
13 (13%)
3-4 degrees
24 (24%)
4-5 degrees
27 (27%)
5-6 degrees
8 (8%)
6-10 degrees
16 (16%)
10-20 degrees
0 (0%)
20-50 degrees
0 (0%)
50-100 degrees
0 (0%)
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Total Members Voted: 97

Author Topic: Magnitude of future warming  (Read 11179 times)

Klondike Kat

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Re: Magnitude of future warming
« Reply #100 on: September 23, 2019, 07:03:18 PM »
Current sequestration is not based on emitted amounts, but on atmospheric concentrations.  As concentrations continue to increase, sequestration should increase to keep pace (similar percentage).  At some point removal will equal addition, such that the conentration will remain constant.  Once emissions fall below the removal rate, atmospheric concentrations will fall.

oren

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Re: Magnitude of future warming
« Reply #101 on: September 23, 2019, 08:35:45 PM »
Again, I am far from knowledgeable on this subject, but I would guess sequestration is also dependent on ocean CO2 level, which has probably risen since the 1970s. Hope someone with more credentials can pitch in.
« Last Edit: September 23, 2019, 08:43:44 PM by oren »

oren

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Re: Magnitude of future warming
« Reply #102 on: September 23, 2019, 08:43:07 PM »
Google to the rescue.

Quote
How the oceans absorb carbon dioxide is critical for predicting climate change
Air-sea gas exchange is a physio-chemical process, primarily controlled by the air-sea difference in gas concentrations and the exchange coefficient, which determines how quickly a molecule of gas can move across the ocean-atmosphere boundary. It takes about one year to equilibrate CO2 in the surface ocean with atmospheric CO2, so it is not unusual to observe large air-sea differences in CO2 concentrations. Most of the differences are caused by variability in the oceans due to biology and ocean circulation. The oceans contain a very large reservoir of carbon that can be exchanged with the atmosphere because the CO2 reacts with water to form carbonic acid and its dissociation products. As atmospheric CO2 increases, the interaction with the surface ocean will change the chemistry of the seawater resulting in ocean acidification.

Evidence suggests that the past and current ocean uptake of human-derived (anthropogenic) CO2 is primarily a physical response to rising atmospheric CO2 concentrations. Whenever the partial pressure of a gas is increased in the atmosphere over a body of water, the gas will diffuse into that water until the partial pressures across the air-water interface are equilibrated. However, because the global carbon cycle is intimately embedded in the physical climate system there exist several feedback loops between the two systems. For example, increasing CO2 modifies the climate which in turn impacts ocean circulation and therefore ocean CO2 uptake. Changes in marine ecosystems resulting from rising CO2 and/or changing climate can also result in changes in air-sea CO2 exchange. These feedbacks can change the role of the oceans in taking up atmospheric CO2 making it very difficult to predict how the ocean carbon cycle will operate in the future.
https://www.pmel.noaa.gov/co2/story/Ocean+Carbon+Uptake

Quote
Ocean Acidification: The Other Carbon Dioxide Problem
Fundamental changes in seawater chemistry are occurring throughout the world's oceans. Since the beginning of the industrial revolution, the release of carbon dioxide (CO2) from humankind's industrial and agricultural activities has increased the amount of CO2 in the atmosphere. The ocean absorbs about a quarter of the CO2 we release into the atmosphere every year, so as atmospheric CO2 levels increase, so do the levels in the ocean. Initially, many scientists focused on the benefits of the ocean removing this greenhouse gas from the atmosphere.  However, decades of ocean observations now show that there is also a downside — the CO2 absorbed by the ocean is changing the chemistry of the seawater, a process called OCEAN ACIDIFICATION.
https://www.pmel.noaa.gov/co2/story/Ocean+Acidification


Florifulgurator

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Re: Magnitude of future warming
« Reply #103 on: September 23, 2019, 08:51:25 PM »
I would guess sequestration is also dependent on ocean CO2 level.
Yes. The other elephant in the room.
Like with thermal inertia there is also CO2 mixing inertia of oceans. Carbon sequestration is a job for centuries.
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Klondike Kat

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Re: Magnitude of future warming
« Reply #104 on: September 23, 2019, 09:33:49 PM »
Again, I am far from knowledgeable on this subject, but I would guess sequestration is also dependent on ocean CO2 level, which has probably risen since the 1970s. Hope someone with more credentials can pitch in.

The sequestering is dependent on the partial pressure of the gas in the atmosphere and dissolved in the ocean.  Carbon dioxide in the atmosphere and dissolved in the ocean will strive to maintain equilibrium.  A change in one will lead to a change in the other.  Much of the gas that has been emitted into the atmosphere has already dissolved into the ocean.  This process with continue towards equilibrium.

oren

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Re: Magnitude of future warming
« Reply #105 on: September 23, 2019, 10:37:35 PM »
KK, I know that you strive hard to prove that things are better than they seem, a commendable goal when sincere, but I feel that in this case you are wrong. As the CO2 is equilibrated into the ocean, its rate of oceanic uptake slows down, in opposition to the way you describe it and to the math you presented above.

Klondike Kat

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Re: Magnitude of future warming
« Reply #106 on: September 23, 2019, 11:00:57 PM »
Oren, that would be the case if the equilibrium was fast and the atmospheric lifetime of CO2 was short.  These calculations are based on the premise that the lifetime is long, and the equilibrium is slow.  I am not the expert on the atmospheric lifetime of CO2, but am using the conclusions of others.  However, if the premise of a long lifetime is correct, then the ocean will continue to sequester CO2 for quite some time.  I am a chemist, not a biologist, so I cannot comment as readily about terrestrial sequestration.

sidd

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Re: Magnitude of future warming
« Reply #107 on: September 24, 2019, 06:20:41 AM »
It is true that ocean surface water will sequester CO2 at a rate proportional to difference of CO2 partial pressure between atmosphere and surface ocean.  Absent anything else, this rate will slow down as the difference goes to zero.

But ofcourse there are many,many anything elses. Carbonate equilibrium is one. Coccolithophores are another. The latter will dwindle as pH goes up reducing deep ocen sequestration. That's just one of the million feedbacks we are beginning to understand.

So i am not sanguine that the land and ocean sequestration we see today will continue. I am concerned about land sinks even more than ocean. It is increasingly clear that land sinks may easily turn into sources.

At present, half our fossil C emissions are sequestered by "natural" processes. If those take a hit, keeling curve will go up faster, as will radiative imbalance, warming and ecosystem impact.

sidd


Klondike Kat

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Re: Magnitude of future warming
« Reply #108 on: September 24, 2019, 01:22:33 PM »
Land and ocean sequestrations that are based on physical properties will not change as CO2 concentrations rise.  This is straight-forward chemistry.  These natural processes will not change.  The one process that may change is the biological sequestration.  Deforestation has added significantly to the increase in atmospheric carbon dioxide levels.  Fortunately, this has been recognized and efforts have been made to restore the forests (for habitat restoration purposes also).  This has fared much better than efforts to reduce carbon dioxide emissions. 

In the U.S., 26% of the forests were cut down by 1910 - mostly for agriculture.  Since then, the forested area has increased slightly (about 2%).  Europe has had much higher levels of deforestation, with some estimates at ~90%.  In recent years, thes temporal forests have been making a comeback, with reforestation efforts increasnig forested lands in both Europe and Asia.  Unfortunately, trends in tropical Africa and South America have countered these efforts.  Still, there is hope in reforestation efforts, which would increase land sequestration of carbon dioxide.  Hence, it seems more likely that sinks would increase in the coming years, rather than decrease.

https://ourworldindata.org/forests

gerontocrat

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Re: Magnitude of future warming
« Reply #109 on: September 24, 2019, 02:17:54 PM »
Future of land & ocean sinks

Everything changes all the time. Nothing is constant.

Below is some data about recent changes in the Southern Ocean uptake of CO2, currently increasing but for how long?

Elsewhere I found and lost a paper on that Ocean sinks work in 2 ways, on the chemical process discussed below, and biological processes - mostly by small organisms - e.g. algae. Photosynthesis traps carbon, organisms die, carbon trapped in the ocean floor sediments. Mankind is not being kind to life in the oceans.

As for the land sinks, planting trees by one part of mankind, destroying forests by another. Permafrost? Tundra?

Who knows what the net effect of all these changes will be.

__________________________________________________________
https://www.carbonbrief.org/scientists-solve-ocean-carbon-sink-puzzle

Scientists solve ocean ‘carbon sink’ puzzle

Quote
A new study, published in Nature, finds that recent changes in circulation patterns in the world’s oceans are playing a key role in how much CO2 they take up.

Weakening circulation patterns have boosted how much CO2 the oceans absorb since the 2000s, the researchers say, but there’s no guarantee that this will continue into the future.
 


the amount of CO2 that the oceans absorb isn’t constant. In the 1990s, ocean CO2 uptake dropped off, before increasing again in the 2000s. Recent research shows that the Southern Ocean was central to these changes.

The Southern Ocean is the most prolific of the oceans for carbon storage – accounting for approximately 40% of the global ocean CO2 uptake. In the 1990s, strengthening winds circulating around Antarctica affected ocean currents and brought carbon-rich water to the surface. This meant the ocean was less able to absorb CO2 from the atmosphere.

In the 2000s, the winds continued to strengthen, yet the CO2 uptake in the Southern Ocean rebounded. This, combined with increasing CO2 uptake in other oceans, suggested to scientists that there was, ultimately, another factor affecting the ocean carbon sink.

The new study says the reason lies in circulation patterns in the top 1,000m of the world’s oceans.

‘Missing piece of the puzzle’
The water in our oceans is constantly on the move. In the upper layers of the ocean there are several driving forces responsible, explains lead author Dr Tim DeVries, an assistant professor in oceanography at the University of California. He tells Carbon Brief:

“The [circulation patterns] are driven by winds and by ‘buoyancy forcing’ – which means changes in the density of surface waters due to changes in their temperature (heating/cooling) or salinity (adding/removing freshwater).”

Using observed data, the researchers built a computer model to simulate these circulation patterns in the upper ocean. They ran their model to analyse the exchange of CO2 between the ocean and atmosphere over recent decades.

They found that in the 1990s, the ocean circulation patterns were “more vigorous” and coincided with a big dip in CO2 uptake. From around 2000, the circulation patterns then weakened, bringing a rebound in CO2 uptake.

The simplified diagram below illustrates the effect these “overturning” circulation patterns have.

Stronger ocean overturning – as seen during the 1990s – brings more carbon-rich water up from the deeper ocean, the researchers say. When this water reaches the surface it releases CO2 into the atmosphere (see a). More vigorous overturning also means the ocean takes up more CO2 from the atmosphere (b), but not as much as the extra CO2 released.

As the bottom half of the diagram shows, weaker overturning in the 2000s reduces both the amount of CO2 released to the atmosphere (c), and what is absorbed again (d). Overall, this increases how much CO2 the ocean takes up.
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Klondike Kat

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Re: Magnitude of future warming
« Reply #110 on: September 24, 2019, 03:42:33 PM »
Very nice gerontocrat.  The only constant in life is change - Heraclitus.

That said, we cannot predict what changes will occur.  In the absence of a known change, we assume a constant to minimize potential errors.

gerontocrat

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Re: Magnitude of future warming
« Reply #111 on: September 24, 2019, 05:19:11 PM »
So I took the data from NOAA & elsewhere from 1980 to 2018 on Global CO2 ppm & Emissions.

I converted CO2 ppm change to GT change, and from that got the GT sunk in GT & as % of emissions. I then made 10 year trailing averages as the yearly data is so spiky.

Hence the attached graph. The data shows a % and GT drop and then a rise sort of in line with what the science papers are saying about variations due to ocean circulation.

But the main conclusion remains the same, CO2 captured by the sinks increased as emissions increased.

So my question remains the same - will CO2 captured by the sinks decrease as emissions decrease? (or in another way- how sensitive is the chemical process that exchanges CO2 from air to ocean to small changes in CO2 ppm?)


https://link.springer.com/article/10.1007/s40641-018-0104-3
Quote
Models project that when net CO2 emissions are positive, but start to decline, the land and ocean carbon sinks will begin to weaken and take up less CO2 . Note that these responses may not be driven entirely by CO2 forcing as other factors such as a changing climate also affect the strength of these sinks. At some point, as net CO2 emissions decline, carbon sink uptake will exceed emissions input and the atmospheric CO2 concentration will begin to decline.

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Klondike Kat

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Re: Magnitude of future warming
« Reply #112 on: September 24, 2019, 05:55:28 PM »

So my question remains the same - will CO2 captured by the sinks decrease as emissions decrease? (or in another way- how sensitive is the chemical process that exchanges CO2 from air to ocean to small changes in CO2 ppm?)


My answer is not directly.  I stand behind my claim that CO2 captured is a function of the concentration in the atmosphere, not the amount emitted.  When the captured amount exceeds the emitted amount, then the atmospheric concentration will decrease.  That will subsequently lead to decreased capture. 

Hence, it is indirectly related to emitted CO2, as decreasing emissions will eventually result in decreased atmospheric concentration, and consequently decreased capture.

Of course, this cannot be proven until emissions begin to decrease.

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Re: Magnitude of future warming
« Reply #113 on: September 24, 2019, 09:44:56 PM »
Hello all.  Love this thread.  It has been fascinating to follow.

So... I got to wondering and looked up some stuff.  My first question was about the finite-ness of the oceans and wondered if that might be a limiting factor. The information I found (as one might expect) says that this is a complex subject and still too little is known but, but, but....  :o   :o   :o 

Alarmingly also this:
Quote
As long as atmospheric CO2 concentrations continue to rise, the oceans will continue to take up CO2 .
However, this reaction is reversible. If atmospheric CO2 were to decrease in the future, the oceans will start releasing the accumulated anthropogenic CO2 back out into the atmosphere. [emphasis mine]

http://www.waterencyclopedia.com/Bi-Ca/Carbon-Dioxide-in-the-Ocean-and-Atmosphere.html#ixzz60TMnjmHg

Although, it does go on to say:
Quote
The ultimate storage place for anthropogenic CO2 must be reactions that bind the CO2 in a manner that is not easily reversed. Dissolution of calcium carbonate in the oceans, for example, is a long-term storage place for CO2 . As the oceans continue to take up anthropogenic CO2 , it will penetrate deeper into the water column, lowering the pH and making the waters more corrosive to calcium carbonate. The problem is that carbonate dissolution typically occurs in the deep ocean, well removed from the anthropogenic CO2 taken up in the surface waters. In portions of the North Atlantic and North Pacific Oceans, however, anthropogenic CO2 may have already penetrated deep enough to influence the dissolution of calcium carbonate in the water column.
« Last Edit: September 24, 2019, 10:01:23 PM by JMP »

oren

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Re: Magnitude of future warming
« Reply #114 on: September 24, 2019, 11:10:55 PM »
Quote
My answer is not directly.  I stand behind my claim that CO2 captured is a function of the concentration in the atmosphere, not the amount emitted.  When the captured amount exceeds the emitted amount, then the atmospheric concentration will decrease.  That will subsequently lead to decreased capture.  
KK you insist on ignoring the other factor, ocean surface concentration. The uptake of CO2 by the ocean in the near term is proportional to the atmospheric concentration less the ocean surface concentration (including the slower downward flux from the ocean surface to the deep ocean).  But the ocean surface concentration is a function of the past emitted CO2. Thus scrubbing of the CO2 from the atmosphere will be dependent on slower processes (assuming emissions stop at some point).
I expect that as a chemist this really should be crystal clear to you. The ocean surface equilibrates fast, and has already swallowed a lot of CO2, so further fast uptake is dependent on further increase in atmospheric partial pressure.

Klondike Kat

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Re: Magnitude of future warming
« Reply #115 on: September 24, 2019, 11:53:56 PM »
Quote
My answer is not directly.  I stand behind my claim that CO2 captured is a function of the concentration in the atmosphere, not the amount emitted.  When the captured amount exceeds the emitted amount, then the atmospheric concentration will decrease.  That will subsequently lead to decreased capture. 
KK you insist on ignoring the other factor, ocean surface concentration. The uptake of CO2 by the ocean in the near term is proportional to the atmospheric concentration less the ocean surface concentration (including the slower downward flux from the ocean surface to the deep ocean).  But the ocean surface concentration is a function of the past emitted CO2. Thus scrubbing of the CO2 from the atmosphere will be dependent on slower processes (assuming emissions stop at some point).
I expect that as a chemist this really should be crystal clear to you. The ocean surface equilibrates fast, and has already swallowed a lot of CO2, so further fast uptake is dependent on further increase in atmospheric partial pressure.

The gas exchange at the surface is but one aspect of the entire planetary sequestration process.  The mixing of the surface waters with the deep ocean takes much longer, as does calcification and other terrestrial sinks.  We have been operating under the assumption that planetary equilibrium is a slow process, and the atmospheric carbon dioxide lifetime is long.  Are you arguing for a fast equilibrium and short lifetime? 

Hefaistos

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Re: Magnitude of future warming
« Reply #116 on: September 25, 2019, 07:45:04 AM »
The gas exchange at the surface is but one aspect of the entire planetary sequestration process.  The mixing of the surface waters with the deep ocean takes much longer, as does calcification and other terrestrial sinks.  We have been operating under the assumption that planetary equilibrium is a slow process, and the atmospheric carbon dioxide lifetime is long.  Are you arguing for a fast equilibrium and short lifetime?

This topic is covered in AR5, WG1, chapter 9. Here is figure 9.26 on p. 793 showing the ocean part, the upper panel.
"With few exceptions, the CMIP5 ESMs also reproduce the large-scale pattern of ocean–atmosphere CO2 fluxes, with uptake in the Southern Ocean and northern
mid-latitudes, and outgassing in the tropics. However, the geographical
pattern of simulated land–atmosphere fluxes agrees much less well
with inversion estimates, which suggest a larger sink in the northern
mid-latitudes, and a net source rather than a sink in the tropics
." (p. 794)

In the figure we see another clear positive bias in how models estimate the atmosphere to ocean fluxfor such a long period as 1960-2005.

Figure byline to 9.26 Ensemble-mean global ocean carbon uptake (top) and global land carbon uptake (bottom) in the CMIP5 ESMs for the historical period 1900–2005. For comparison,
the observation-based estimates provided by the Global Carbon Project (Le Quere et al., 2009) are also shown (thick black line). The confidence limits on the ensemble mean are
derived by assuming that the CMIP5 models come from a t-distribution. The grey areas show the range of annual mean fluxes simulated across the model ensemble. This figure
includes results from all CMIP5 models that reported land CO2 fluxes, ocean CO2 fluxes, or both (Anav et al., 2013).

mdoliner

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Re: Magnitude of future warming
« Reply #117 on: September 25, 2019, 08:02:11 PM »
Does anybody know the math that connects an amount of warming to a level of greenhouse gases? Heat leaves the planet only through long wavelength radiation, and the amount of such radiation is a function of T4. Since ice melts using heat without raising temperature, the heat imbalance should last until the ice is gone. This is modified by the inefficiency of heat movement, but the ice will eventually melt, cooling the planet and reducing radiation, thus restoring the imbalance between energy in and energy out. It seems to me once this gets going it will continue until the ice is gone.

There is one posssible modification, albedo change. Open water has a lower albedo and so absorbs more radiation than ice. But open water also radiates more heat than ice. These two effects balance when the sun is roughly 13° or lower. Would the extra open water in the arctic be a negative or positive feedback?

nanning

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Re: Magnitude of future warming
« Reply #118 on: September 25, 2019, 08:41:57 PM »
I think that you'll find all the math in the models. There is not one single 'math' in this I think.

I would suggest studying Paleo climate data. That gives a good indication of the conditions in a balanced atmosphere. Right now of course, we don't have a balanced atmosphere. Our exceptionally large anthropogenically forced rate-of-change has no Paleo comparison.

Maybe you'll find this interesting:

On the causal structure between CO2 and global temperature
by Adolf Stips, Diego Macias, Clare Coughlan, Elisa Garcia-Gorriz & X. San Liang

https://www.nature.com/articles/srep21691
(whole article)
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Re: Magnitude of future warming
« Reply #119 on: September 25, 2019, 09:52:32 PM »
Thanks for the reply. I looked at that article. It is concerned with showing a correlation between warming and CO2, but my question is why would it stop at say, 1.5°, when there is still ice to keep the temperature down while more heat is absorbed.

sidd

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Re: Magnitude of future warming
« Reply #120 on: September 25, 2019, 11:19:30 PM »
For discussion on ice, albedo, radiative forcing, see Hansen's "Climate Change and Trace Gases".

https://pubs.giss.nasa.gov/abs/ha02210k.html

sidd

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Re: Magnitude of future warming
« Reply #121 on: September 26, 2019, 08:26:41 PM »
This too offers no justification for saying that the process will stop at, say 1.5 degrees. In the paleorecord warming reversed primarily because of rock weathering, which captured CO2. But that is a slow process (about a gigaton per year), not fast enough for the present situation. Again, since ice melts without raising temperature, and long wave radiation energy emission is a function of temperature, the imbalance should continue until the ice is gone or almost gone.
« Last Edit: September 26, 2019, 08:33:57 PM by mdoliner »

nanning

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Re: Magnitude of future warming
« Reply #122 on: September 27, 2019, 04:19:44 AM »
<snip>
the imbalance should continue until the ice is gone or almost gone.

If you mean the atmosphere with 'imbalance', then I agree. The oceans will keep warming up, driving ever more imbalance. The paleoclimate records show that CO2 and temperature are closely correlated in a balanced atmosphere. We may be undoing the late pliocene glaciation events if the current or higher CO2 level remains in the atmosphere for a long time. Ice as inertia is temporarily 'saving' us. Governing inertia and human behaviour inertia are 'dooming' us.
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mdoliner

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Re: Magnitude of future warming
« Reply #123 on: September 27, 2019, 04:35:20 AM »
I mean by imbalance that there will be more heat coming into the earth via insolation than exits via high wavelength radiation.

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Re: Magnitude of future warming
« Reply #124 on: September 27, 2019, 08:32:29 AM »
Excellent work by Gerontocrat into carbon sinks. However, I am surprised to find the quantity in gigatonne of carbon sunk being on the same axis as percentage sunk given that total emissions are not constant.

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Re: Magnitude of future warming
« Reply #125 on: September 27, 2019, 09:15:33 AM »


On the causal structure between CO2 and global temperature
by Adolf Stips, Diego Macias, Clare Coughlan, Elisa Garcia-Gorriz & X. San Liang

https://www.nature.com/articles/srep21691
(whole article)
'

Thanks Nanning, that is a cool paper!
Employing new methodology of information flow (IF) to test for causation. The issue is that the actual high correlation between rising CO2 levels and increasing surface temperatures alone is insufficient to prove that the increased radiative forcing resulting from the increasing GHG atmospheric concentrations is indeed causing the warming of the earth.
IPCC maintains that ‘detection’ and ‘attribution’ are still regarded as key priorities in climate change research. Correctly so, as GCM models are explicity built on the presumption of such causation, even though they lack fundamental theories and also data on essential things like e.g. water vapor, and aerosols.

Results are unambigious: GHG emissions not only correlate with global warming, they do indeed cause them.

Another very interesting aspect is the regional distribution of the amount of causation: "When analysing the IF from the global anthropogenic forcing to the GMTA (Fig. 3), in the Northern Hemisphere, we identified several regions of significant high causality. For example, IF takes largest values in Europe, North America, and China, densely populated and industrialized areas having shown strong recent warming2. On the other hand there are also regions with high causality like Siberia, the Sahel zone and Alaska that are not that much influenced by human activities. In the Southern Hemisphere, however, this IF distribution displays a most unexpected pattern, with high values in a large swath of the southern Atlantic, South Africa, parts of the Indian Ocean and Australia. This is true for both the total anthropogenic forcing (Fig. 3A) and the radiative forcing caused by CO2 alone (Fig. 3B). Therefore, despite CO2 being a globally well-mixed gas, the IF to surface temperature is regionally very different, showing sensitive areas."

Figure 3 byline: Shown is the spatial distribution of the information flow between the total anthropogenic forcing and the gridded global mean temperature anomalies (GMTA) (A) and the spatial distribution of the information flow between the radiative forcing caused by CO2 and the gridded global mean temperature anomalies (GMTA) (B).

gerontocrat

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Re: Magnitude of future warming
« Reply #126 on: October 01, 2019, 08:18:55 PM »
Excellent work by Gerontocrat into carbon sinks. However, I am surprised to find the quantity in gigatonne of carbon sunk being on the same axis as percentage sunk given that total emissions are not constant.
It isn't.

Percentages - refer to the right axis (green)
Amounts in GT - refer to the left axis (red).

Revised graph attached with amount left in atmosphere (in GT) added. (Also after rooting around online found a better figure to convert CO2 ppm to CO2 Gigatons - minor change).

Note that as regards percentages of CO2 sunk, the most often quoted figures are 30% Ocean, 26% Land, Total Percent of Emissions captured 56%.

The ten year average on 1980 to 2019 data is never higher than just over 52%.

If 2019 data ends up in line with current estimates, the percent of CO2 captured in 2019 will be only about 42%
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Re: Magnitude of future warming
« Reply #127 on: June 14, 2020, 05:33:15 PM »
Climate worst-case scenarios may not go far enough, cloud data shows

Quote
Worst-case global heating scenarios may need to be revised upwards in light of a better understanding of the role of clouds, scientists have said.

...


“That is a very deep concern,” Johan Rockström, the director of the Potsdam Institute for Climate Impact Research, said. “Climate sensitivity is the holy grail of climate science. It is the prime indicator of climate risk. For 40 years, it has been around 3C. Now, we are suddenly starting to see big climate models on the best supercomputers showing things could be worse than we thought.”

He said climate sensitivity above 5C would reduce the scope for human action to reduce the worst impacts of global heating. “We would have no more space for a soft landing of 1.5C [above preindustrial levels]. The best we could aim for is 2C,” he said.

...

Timothy Palmer, a professor in climate physics at Oxford University and a member of the Met Office’s advisory board, said the high figure initially made scientists nervous. “It was way outside previous estimates. People asked whether there was a bug in the code,” he said. “But it boiled down to relatively small changes in the way clouds are represented in the models.”

The role of clouds is one of the most uncertain areas in climate science because they are hard to measure and, depending on altitude, droplet temperature and other factors, can play either a warming or a cooling role. For decades, this has been the focus of fierce academic disputes.

Previous IPCC reports tended to assume that clouds would have a neutral impact because the warming and cooling feedbacks would cancel each other out. But in the past year and a half, a body of evidence has been growing showing that the net effect will be warming. This is based on finer resolution computer models and advanced cloud microphysics.

...

The IPCC is expected to include the 5+C climate sensitivity figure in its next report on the range of possible outcomes. Scientists caution that this is a work in progress and that doubts remain because such a high figure does not fit with historical records.

...

Link >> https://www.theguardian.com/environment/2020/jun/13/climate-worst-case-scenarios-clouds-scientists-global-heating
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Re: Magnitude of future warming
« Reply #128 on: June 14, 2020, 05:45:57 PM »
One has to wonder it very small changes in the way clouds are considered makes such a huge difference in climate sensitivity, what would happen if those small changes were opposite in magnitude.

kassy

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Re: Magnitude of future warming
« Reply #129 on: June 14, 2020, 06:28:41 PM »
Previous IPCC reports tended to assume that clouds would have a neutral impact because the warming and cooling feedbacks would cancel each other out. But in the past year and a half, a body of evidence has been growing showing that the net effect will be warming. This is based on finer resolution computer models and advanced cloud microphysics.

So actually doing the maths on clouds shows they have a non neutral impact.

In a recent paper in the journal Nature, Palmer explains how the new Hadley Centre model that produced the 5+C figure on climate sensitivity was tested by assessing its accuracy in forecasting short-term weather.

This seems to be a good test:
https://www.nature.com/articles/d41586-020-01484-5

Pliocene weather is interesting for clouds too.

There is no opposite in magnitude because calculating less then not calculating is not really a magnitude.

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Re: Magnitude of future warming
« Reply #130 on: June 15, 2020, 12:45:18 AM »
Previous IPCC reports tended to assume that clouds would have a neutral impact because the warming and cooling feedbacks would cancel each other out. But in the past year and a half, a body of evidence has been growing showing that the net effect will be warming. This is based on finer resolution computer models and advanced cloud microphysics.

So actually doing the maths on clouds shows they have a non neutral impact.

In a recent paper in the journal Nature, Palmer explains how the new Hadley Centre model that produced the 5+C figure on climate sensitivity was tested by assessing its accuracy in forecasting short-term weather.

This seems to be a good test:
https://www.nature.com/articles/d41586-020-01484-5

Pliocene weather is interesting for clouds too.

There is no opposite in magnitude because calculating less then not calculating is not really a magnitude.

It is just a matter of semantics.  One could argue that less vs more is opposite in magnitude.  Regardless, they are claiming that the shortwave radiative effect (SCRE) will be less with future warming, although they state that the clouds will have a higher water content.  That seems opposite to established climate science, whereby increased water content leads to increased SCRE.

Hefaistos

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Re: Magnitude of future warming
« Reply #131 on: June 15, 2020, 09:49:28 AM »
This recent research finds a negative feedback for clouds in the ever important tropics.

The lightness of water vapor helps to stabilize tropical climate

Seth D. Seidel and Da Yang

Science Advances  06 May 2020:
Vol. 6, no. 19, eaba1951
DOI: 10.1126/sciadv.aba1951

Abstract
"Moist air is lighter than dry air at the same temperature, pressure, and volume because the molecular weight of water is less than that of dry air. We call this the vapor buoyancy effect. Although this effect is well documented, its impact on Earth’s climate has been overlooked. Here, we show that the lightness of water vapor helps to stabilize tropical climate by increasing the outgoing longwave radiation (OLR). In the tropical atmosphere, buoyancy is horizontally uniform. Then, the vapor buoyancy in the moist regions must be balanced by warmer temperatures in the dry regions of the tropical atmosphere. These higher temperatures increase tropical OLR. This radiative effect increases with warming, leading to a negative climate feedback. At a near present-day surface temperature, vapor buoyancy is responsible for a radiative effect of 1 W/m2 and a negative climate feedback of about 0.15 W/m2 per kelvin."

There is no settled science regarding the feedback of clouds and water vapor. In some situations/some places it's a negative feedback, in others it's a positive feedback.

GCM models are inherently unable to model convectice processes, as they operate on grid sizes that are about 1000 times bigger than the actual processes. Thus, the GCMs resort to parametrization of these processes. In other words, GIGO modelling.

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Re: Magnitude of future warming
« Reply #132 on: June 15, 2020, 01:31:25 PM »
Hefaistos,
I couldn't agree with you more. 

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Re: Magnitude of future warming
« Reply #133 on: June 15, 2020, 02:49:49 PM »
Quote
GCM models are inherently unable to model convectice processes, as they operate on grid sizes that are about 1000 times bigger than the actual processes. Thus, the GCMs resort to parametrization of these processes. In other words, GIGO modelling.

The Hadley validation test shows that if they use their cloud model parameter in short term weather forecasting it improves the forecasts so that is a hint that it actually works (similar to how they used the method to disprove another model challenge earlier).

And of course there are multiple levels on which we can take this.

 You are critical of the model. Fine. But...
Do you think the neutral assumption was more true then what we calculate? Or is it more a problem of magnitudes?
Is the GIGO postulation analysis driven or just because you don´t want it to be true?

I find GIGO kind of harsh. This is complicated stuff which needs tons of computing power.

Quote
Regardless, they are claiming that the shortwave radiative effect (SCRE) will be less with future warming, although they state that the clouds will have a higher water content.  That seems opposite to established climate science, whereby increased water content leads to increased SCRE.

Do you have a quote for that with a link to a paper?
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Re: Magnitude of future warming
« Reply #134 on: June 15, 2020, 04:32:04 PM »


Quote
Regardless, they are claiming that the shortwave radiative effect (SCRE) will be less with future warming, although they state that the clouds will have a higher water content.  That seems opposite to established climate science, whereby increased water content leads to increased SCRE.

Do you have a quote for that with a link to a paper?

I did not feel that I need a link to reference established science, but here goes:

https://earthobservatory.nasa.gov/features/Clouds

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Re: Magnitude of future warming
« Reply #135 on: June 15, 2020, 10:04:26 PM »
You need to link to where the people in the new research claim that: the shortwave radiative effect (SCRE) will be less with future warming, although they state that the clouds will have a higher water content.  That seems opposite to established climate science, whereby increased water content leads to increased SCRE.

Or where you think they do. Not some general background site with Alta Vista vibes.




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Re: Magnitude of future warming
« Reply #136 on: June 16, 2020, 02:24:04 AM »
At least +4C, possibly up to +6C. Climate models are too imperfect to predict such things to great precision, especially on a timescale so far out. However, if events thus far have told us anything, climate models tend to underestimate the outcome due to lacking enough variables to make a proper projection. So I think I tend towards worse case scenarios.

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Re: Magnitude of future warming
« Reply #137 on: June 16, 2020, 03:33:55 AM »
You need to link to where the people in the new research claim that: the shortwave radiative effect (SCRE) will be less with future warming, although they state that the clouds will have a higher water content.  That seems opposite to established climate science, whereby increased water content leads to increased SCRE.

Or where you think they do. Not some general background site with Alta Vista vibes.

I am a tad confused with your post.  Why would I want to link to a claim that SCRE will be less with increased cloud cover, when it seems opposite to established science?

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Re: Magnitude of future warming
« Reply #138 on: June 16, 2020, 07:08:33 AM »
Quote
GCM models are inherently unable to model convectice processes, as they operate on grid sizes that are about 1000 times bigger than the actual processes. Thus, the GCMs resort to parametrization of these processes. In other words, GIGO modelling.

The Hadley validation test shows that if they use their cloud model parameter in short term weather forecasting it improves the forecasts so that is a hint that it actually works (similar to how they used the method to disprove another model challenge earlier).

And of course there are multiple levels on which we can take this.

 You are critical of the model. Fine. But...
Do you think the neutral assumption was more true then what we calculate? Or is it more a problem of magnitudes?
Is the GIGO postulation analysis driven or just because you don´t want it to be true?

I find GIGO kind of harsh. This is complicated stuff which needs tons of computing power.

I have written at some length about this, and about the challenges facing the models before, in a number of posts. To sum up the arguments:

Model makers face 4 major challenges, as I see it:
1. GCM's lack a 'general theory' on water vapor on various latitudes and altitudes. Specifically, the tropics are challenging with the very powerful, energy intensive phase changes taking place (e.g. in the ubiquitos tropical thunderstorms).

2. There is a lack of understanding on the radiative forcing of clouds/water vapor. Is there a positive feedback, or a negative feedback between clouds and SST's? No-one knows. Recent research indicates that the feedback is negative in the tropics, but positive elsewhere. Specifically, IPCC doesn't know, and has previously just assumed that the feedback is zero. Yes, maybe better like that, than rely on GIGO models.

3. GCM's don't have the input data for the strongest GHG (water vapor/clouds) as they operate on MUCH larger grids than clouds, and the convective processes in clouds (currently a factor of more than 1000 between needed grid size, and feasible grid size). Thus, they have to rely on parameterizations for clouds and water vapor. That is a substandard practice, typical for GIGO models.

4. Computing capacity isn't big enough. Witness the GCM model E3SM, where they have severe restrictions on the length of runs they can make, and the number of runs they can afford, in terms of computing capacity and work time involved. GCMs typically use 100 km grid cells, whereas modelling of convective activity would require something like 0.1 km - 1 km cells. To reach this definition in a GCM would require in the order 10^10 times more powerful computers, as well as correspondig feed of input data. This won't happen in any foreseeable future.

All these challenges are clearly solvable, but I'd guess we need a couple of decades to get models that are more reliable as forecasting tools.

It's very disturbing that the enormous range of possible ECS's persists between these models. Currently, with AR5 and CMIP5, the range is from 1.5 - 4.5. And now we have the newer CMIP6 models, where maybe a fourth of them push for even higher ECS, up to 5.5 or so. But still, there are other CMIP6 models that maintain a ECS of 1.5 or so. Thus, the range seems to increase in the near future, in IPCC's AR6 Synthesis Report due in 2022. This is bizarre! How can we build a climate policy on such imprecise tools?!

As IPCC lacks tools for evaluating the quality and performance of models, and has decided to resort to give each model 'one vote', and together they form an ensemble of models. The hope is that the problems that different models have will be averaged out. This is a very crude approach. 

https://forum.arctic-sea-ice.net/index.php/topic,2205.msg234634.html#msg234634
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg231232.html#msg231232
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg232206.html#msg232206
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg243866.html#msg243866
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg237028.html#msg237028

KiwiGriff

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Re: Magnitude of future warming
« Reply #139 on: June 16, 2020, 09:58:40 AM »
Quote
It's very disturbing that the enormous range of possible ECS's persists between these models. Currently, with AR5 and CMIP5, the range is from 1.5 - 4.5

CMIP5 models do not have a range encompassing 1.5C that lower bound is only derived from observational based modeling of ECS.
I doubt that a lower bound of 1.5C will hold into AR6 as much work has been published attempting to reconcile the low results of some observational based models with other methods.
https://www.carbonbrief.org/explainer-how-scientists-estimate-climate-sensitivity


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Re: Magnitude of future warming
« Reply #140 on: June 16, 2020, 02:45:09 PM »
2. There is a lack of understanding on the radiative forcing of clouds/water vapor. Is there a positive feedback, or a negative feedback between clouds and SST's? No-one knows. Recent research indicates that the feedback is negative in the tropics, but positive elsewhere. Specifically, IPCC doesn't know, and has previously just assumed that the feedback is zero. Yes, maybe better like that, than rely on GIGO models.

We could sure do with more computing power. It´s not even that expensive.

I still disagree with the last part.

What they added is not perfect but it is not garbage either.

If you take your argument to the extreme that would mean you could never add new things to models and that is clearly wrong.
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Re: Magnitude of future warming
« Reply #141 on: June 16, 2020, 09:22:27 PM »
Re: models

This preprint is relevant:

https://arxiv.org/pdf/2005.11862.pdf

sidd

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Re: Magnitude of future warming
« Reply #142 on: June 16, 2020, 11:44:45 PM »
And Gavin Schmidt, a climate modeler, at Real Climate has provided an update as well:

http://www.realclimate.org/index.php/archives/2020/06/sensitive-but-unclassified-part-ii/

Quote
Sensitive but unclassified: Part II
— gavin @ 13 June 2020

The discussion and analysis of the latest round of climate models continues – but not always sensibly.

Quote
Since then, more model results have been added to the archive, and thanks to Mark Zelinka, we can see some of the analysis as it updates in real time.



Quote
By eye, it looks like there are two (or three) groups of models, one within the range of the assessed values (roughly 2 to 4.5ºC), one group with significantly higher values, and one institution/two models with a notably lower ECS. The question everyone has is whether this extended range is credible.

Quote
Since my first post, there have been a number of papers have looked at the skill of these models to see whether there are some key observational data that might help in constraining the sensitivity (and by extension, the projections into the future). One set of papers has focused on the global mean trends from 1990 or so onward which is a period of stable or declining aerosol trends and which might therefore be a closer test of the models’ transient sensitivity to CO2 than earlier periods. Notably Tokarska et al. (2020) and Njisse et al. (2020) suggest that many of the high ECS group warm substantially faster than observed over this period and therefore should be downweighted in the constrained projections of the future.



Quote
Recently however, writing in Guardian, Jonathan Watts uses results from the UK’s new model (Williams et al., 2020) and a commentary from Tim Palmer to argue that that we nonetheless need to take these high sensitivities more seriously, and indeed that they may indicate that the assessed ECS range has been underestimating potential changes in the future. This is however flawed.

The Williams et al paper demonstrates that updates to the HadGEM3‐GC3.1 model developed by the UK’s Hadley Centre that affect the clouds and aerosols, increase the skill of that model in short-term initialized weather forecasts. This is fine, and indeed, consistent with increases in skill in the newer models across the board when they are compared to a very broad range of observations.

But it is a logical leap to go from an observation of increased skill in one metric to assuming that therefore the overall ECS in this particular model is more likely. To demonstrate that, one would need to show that this particular measure of skill was specifically related to ECS which has not been done (a point Palmer acknowledges). To put in another way, it may be that all models that do well on this task have a range of ECS values, and that the coincidence of this one model doing well and having a high ECS, was just that, a coincidence.

The article goes into details about cloud water and the impact on sensitivity.  If you're interested, it's worth going over to the link to see why.

tl,dr:  The jury is still out on the high sensitivity models.

Hefaistos

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Re: Magnitude of future warming
« Reply #143 on: June 17, 2020, 07:20:15 AM »
Quote
It's very disturbing that the enormous range of possible ECS's persists between these models. Currently, with AR5 and CMIP5, the range is from 1.5 - 4.5

...
I doubt that a lower bound of 1.5C will hold into AR6 as much work has been published attempting to reconcile the low results of some observational based models with other methods.
https://www.carbonbrief.org/explainer-how-scientists-estimate-climate-sensitivity


You refer to an overview article in Carbonbrief. In that article they make a central claim regarding the most influential GHG, water vapour: "As the world warms, the amount of water vapour in the atmosphere is expected to increase and, therefore, so too will the greenhouse effect. Measurements from satellites confirm that water vapour concentrations have been increasing in step with temperatures in the atmosphere over the past few decades." , with a link to:
https://www.gfdl.noaa.gov/blog_held/48-increasing-vertically-integrated-water-vapor-over-the-oceans/
At the link, there is a chart that shows very slightly increasing water vapor over the oceans, but only in the tropics.
However, the data is not that straightforward, nor is it simple to interpret. At the NOAA Physical Sciences Laboratory (PSL) you can create charts of humidity. Relative atmospheric humidity (%) at three different altitudes in the lower part of the atmosphere (the Troposphere) is generally speaking going down.
Also specific atmospheric humidity (g/kg) is down on higher altitudes, and shows the stipulated uptrend only at surface level.
https://psl.noaa.gov/cgi-bin/data/timeseries/timeseries1.pl

Conflicting evidence regarding water vapour feedback!

We also have recent research showing that the cloud feedback in the tropics is negative. Already mentioned upthread, the paper by Seidel and Yang, in Science Advances  06 May 2020: DOI: 10.1126/sciadv.aba1951
https://forum.arctic-sea-ice.net/index.php/topic,2715.msg268667.html#msg268667

Conflicting evidence also regarding cloud feedback!

There are already several critical scientific evaluations of the CMIP6 models. Zelinka et al write:
"ECS is higher on average in CMIP6 due primarily to strengthened cloud feedbacks. Tropical low cloud feedbacks and global non‐low cloud feedbacks are positive in nearly every model."
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL085782

What if the CMIP models didn't get their physical processes right? What if the feedback in the most important sector, the tropics, is negative, as Seidel and Yang show?

Then it is the high ECS models that should be discarded, not the low ECS ones.

kassy

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Re: Magnitude of future warming
« Reply #144 on: June 18, 2020, 01:41:00 AM »
Nobody questions the first claim.

Quote
At the link, there is a chart that shows very slightly increasing water vapor over the oceans, but only in the tropics.
However, the data is not that straightforward, nor is it simple to interpret. At the NOAA Physical Sciences Laboratory (PSL) you can create charts of humidity.

Models very robustly maintain more or less constant relative humidity in these lower tropospheric layers over the oceans as they warm, basically due to the constraint imposed by  the energy balance of the troposphere on the strength of  the hydrological cycle, and the tight coupling between the latter and the low level relative humidity over the oceans.  Do we have observational evidence for this behavior?  The answer is a definitive yes, as indicated by the plot above of microwave measurements of total column water vapor compared to model simulations of the same quantity.

So the graphic is about 2 records agreeing.

It is also quite noisy but that fits with the water cycle.

I don´t think these graphics tell you much for two reasons.

1) For now this proces is stable but noisy as the graph shows. In the long term the signal will be modulated by CO2 piling up above the water vapor and methane changing to co2 + water high in the atmosphere.

2) The data set you get to play with goes from 1950 - 2020. Over that time frame the CO2 and CH4 effects are only present on the end of the range but not in a way they are detectable in your chosen metrics.
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kassy

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Re: Magnitude of future warming
« Reply #145 on: June 18, 2020, 02:47:09 AM »
Something bug me about ECS

The equilibrium climate sensitivity (ECS) is the long-term temperature rise (equilibrium global mean near-surface air temperature) that is expected to result from a doubling of the atmospheric CO2 concentration (ΔT2×). It is a prediction of the new global mean near-surface air temperature once the CO2 concentration has stopped increasing and most of the feedbacks have had time to have their full effect. Reaching an equilibrium temperature can take centuries, or even millennia, after CO2 has doubled.

As we can see above clouds are a contentious issue but the actual land modelling isn´t that great either. Recent research has turned up a number of processes from permafrost that are not modelled (NO2 and carbon release via surface water).

We are awaking all kinds of earth processes we do not really understand and i think it is safe to say we constantly underestimate the consequences.

So we use ECS to see how bad it wil get. Theoretically ok but.

The real glaring problem is that in the whole IPCC proces they never set solid boundaries. What is acceptable damage?

Real sensible goals would be:
Prevent arctic ice from melting.
Prevent permafrost from becoming a source.
Prevent Antarctic glaciers becoming active.

We failed all those already at the current temperatures so technically we are in overshoot since CO2 hit 350 to 380 ppm. It´s rather hard to put a number on ECS if you have to account for all those things.

It is also redundant. It´s like standing in the garden and trying to run some numbers on the fire in the house.
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Human Habitat Index

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Re: Magnitude of future warming
« Reply #146 on: June 18, 2020, 03:24:56 AM »
In my opinion based on following climate change since the 70s is that ECS, like the uncertainty of the preindustrial baseline, is a tool for obfuscation.

Why the doubling of co2, what is magical about that standard ?

After Copenhagen, I became a raging conspiracy theorist, leading me to discover many inconvenient truths in many areas besides CC.

But overall the momentum of industrial civilisation just overwhelms everything.

So I am a rational doomist because the situation is irreversible.
There is a principle which is a bar against all information, which cannot fail to keep a man in everlasting ignorance. That principle is contempt prior to investigation. - Herbert Spencer

KiwiGriff

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Re: Magnitude of future warming
« Reply #147 on: June 18, 2020, 04:01:06 AM »
https://archive.ipcc.ch/publications_and_data/ar4/wg1/en/ch3s3-4-2-2.html

In general, the radiosonde trends are highly suspect owing to the poor quality of, and changes over time in, the humidity sensors (e.g., Wang et al., 2002a). Comparisons of water vapour sensors during recent intensive field campaigns have produced a renewed appreciation of random and systematic errors in radiosonde measurements of upper-tropospheric water vapour and of the difficulty in developing accurate corrections for these measurements (Guichard et al., 2000; Revercombe et al., 2003; Turner et al., 2003; Wang et al., 2003; Miloshevich et al., 2004; Soden et al., 2004).

https://www.ipcc.ch/site/assets/uploads/2018/07/WGI_AR5.Chap_.2_SM-1.pdf
2.SM.6.2 Radiosonde Humidity Data
Since AR4 there have been three distinct efforts to homogenize the
tropospheric humidity records from operational radiosonde measurements (Durre et al., 2009; McCarthy et al., 2009; Dai et al., 2011) (Table
2.SM.9)


Abstract
[1] In an effort to update previous analyses of long‐term changes in column‐integrated water vapor, we have analyzed trends in surface‐to‐500‐hPa precipitable water (PW) calculated from radiosonde measurements of dew point depression, temperature, and pressure at approximately 300 stations in the Northern Hemisphere for the period 1973–2006. Inhomogeneities were addressed by applying a homogenization algorithm that adjusts for both documented and undocumented change points. The trends of the adjusted PW time series are predominantly upward, with a statistically significant trend of 0.45 mm decade−1 for the Northern Hemisphere land areas included in the analysis. Particularly significant increases are found in all seasons over the islands of the western tropical Pacific, and trends are also positive and statistically significant for the year as a whole and in at least one season in Japan and the United States. These results indicate that the widespread increases in tropospheric water vapor, which earlier studies had reported and shown to be physically consistent with concurrent increases in temperature and changes in moisture transport, have continued in recent years.
Radiosonde‐based trends in precipitable water over the Northern Hemisphere: An update
Imke Durre  Claude N. Williams Jr.  Xungang Yin  Russell S. Vose
First published:13 March 2009

Abstract
A new analysis of historical radiosonde humidity observations is described. An assessment of both known and unknown instrument and observing practice changes has been conducted to assess their impact on bias and uncertainty in long-term trends. The processing of the data includes interpolation of data to address known sampling bias from missing dry day and cold temperature events, a first-guess adjustment for known radiosonde model changes, and a more sophisticated ensemble of estimates based on 100 neighbor-based homogenizations. At each stage the impact and uncertainty of the process has been quantified. The adjustments remove an apparent drying over Europe and parts of Asia and introduce greater consistency between temperature and specific humidity trends from day and night observations. Interannual variability and trends at the surface are shown to be in good agreement with independent in situ datasets, although some steplike discrepancies are apparent between the time series of relative humidity at the surface. Adjusted trends, accounting for documented and undocumented break points and their uncertainty, across the extratropical Northern Hemisphere lower and midtroposphere show warming of 0.1-0.4 K decade(-1) and moistening on the order of 1%-5% decade (1)since 1970. There is little or no change in the observed relative humidity in the same period, consistent with climate model expectation of a positive water vapor feedback in the extratropics with near-constant relative humidity.

An Analysis of Tropospheric Humidity Trends from Radiosondes
Article (PDF Available) in Journal of Climate 22(22):5820-5838 · November 2009 with 76 Reads 
DOI: 10.1175/2009JCLI2879.1
Cite this publication
Mark P. McCarthy Et.al



One could look towards data we believe is reasonably accurate rather than relying on that we know is not.

Hefaistos

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Re: Magnitude of future warming
« Reply #148 on: June 18, 2020, 11:50:06 AM »
In my opinion based on following climate change since the 70s is that ECS, like the uncertainty of the preindustrial baseline, is a tool for obfuscation.

Why the doubling of co2, what is magical about that standard ?
...

Global annual mean CO2 concentration has increased by almost 50% since the start of the Industrial Revolution, from 280 ppm to 420 ppm now.
Doubling of CO2 means another 140 ppm to add. Currently we add maybe 2.2 ppm per year, and it has become a linear growth. So in 50 - 70 years with continued linear growth we will have doubled the CO2. Kind of graspable.

Testing with GCM models for the effects of a doubling of CO2 thus makes a lot of sense, per se.

KiwiGriff

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Re: Magnitude of future warming
« Reply #149 on: June 18, 2020, 02:09:15 PM »
Care to prove the keeling curve is now linear?
Or is that just your eyeballs?
https://scripps.ucsd.edu/programs/keelingcurve/2019/06/04/carbon-dioxide-levels-hit-record-peak-in-may/
Carbon Dioxide Levels Hit Record Peak in May
Quote
In Climate in the News, Keeling Curve History, Measurement Notes by Rob MonroeJune 4, 2019

Monthly average surpassed 414 parts per million at Mauna Loa Observatory

Atmospheric carbon dioxide continued its rapid rise in 2019, with the average for May peaking at 414.8 parts per million (ppm), according to instruments operated by Scripps Institution of Oceanography at the University of California San Diego at NOAA’s Mauna Loa Atmospheric Baseline Observatory, scientists from NOAA and Scripps announced today.

This is the highest seasonal peak recorded in 61 years of observations on top of Hawaii’s largest volcano, and the seventh consecutive year of steep global increases in concentrations of carbon dioxide, or CO2. The 2019 peak value was 3.5 parts per million higher than the 411.3 ppm peak reached in May 2018; it represents the second-highest annual jump on record.

Monthly CO2 values at Mauna Loa first breached the 400 ppm threshold in 2014.

May 2020:       417.07 ppm

https://scripps.ucsd.edu/programs/keelingcurve/