What is the correct value of Climate Sensitivity?

[On Guard for Thee]

How am I a 'naysayer'? Although I understand why you try to label me as such. Maintaining the belief in a false dichotomy is one of the primary mechanisms by which alarmists maintain their absurd belief system. To acknowledge the existence of a position outside of the false dichotomy would be committing blasphemy.

What's your source? Mine is http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter13_FINAL.pdf. I gave the 95% confidence interval.

The IPCC may be biased, but they are not orders of magnitude wrong. For example, they have a tendency to overstate climate sensitivity, they use GCM models such as CIMP5 (which gives a mean climate sensitivity estimate of ~3.2C) to make climate predictions, and they use emission scenarios that tend to overstate expected GHG levels over the century (RCP 8.5 is complete nonsense for example). However, they have to maintain some scientific accuracy and they do contribute to human knowledge on climate change.

I guess if you think studying the science that points to the existence of GW is absurd, then that is up to you. However trying to ignore what a vast majority of the peer reviewed reports present may actually be absurd. Anyway here is one of my sources...

http://www.climatecentral.org/news/greenland-glaciers-melt-sea-level-rise-17457

[-1=e^ipi]

I guess if you think studying the science that points to the existence of GW is absurd, then that is up to you.

So nothing I have done in this thread counts as studying science? Anyway, nice dodge on avoiding acknowledging the existence of positions outside of the false dichotomy.

However trying to ignore what a vast majority of the peer reviewed reports present may actually be absurd. Anyway here is one of my sources...

http://www.climatecentral.org/news/greenland-glaciers-melt-sea-level-rise-17457

So apparently some journalist (and it's not like journalists are biased or anything...) apparently trumps chapter 13 of the IPCC's AR5? And apparently we are suppose to throw confidence intervals out the window and perform rounding error to overstate sea level rise?

[On Guard for Thee]

So nothing I have done in this thread counts as studying science? Anyway, nice dodge on avoiding acknowledging the existence of positions outside of the false dichotomy.

So apparently some journalist (and it's not like journalists are biased or anything...) apparently trumps chapter 13 of the IPCC's AR5? And apparently we are suppose to throw confidence intervals out the window and perform rounding error to overstate sea level rise?

Maybe you dont know much about Climate Central if you just think they are just journalists. But its not uncommon that people attempt to ignore sources that oppose their ideas. Its quite common actually. Trouble is that the alarmists as the term some like to use, as if it makes any difference to the science, seem to make up the ever growing majority of the peer reviewed studies. maybe its telling us we ought to get a bit alarmed.

[TimG]

Trouble is that the alarmists as the term some like to use, as if it makes any difference to the science, seem to make up the ever growing majority of the peer reviewed studies.

Not really. It really depends on the topic. For example, when it come to the question of the impact of climate change on extreme weather events the alarmists are a minority. The scientific consensus is there is no evidence of any impact, however, it is possible that the impact will be observable in the future but only if you believe the climate models are not exaggerating. Also, as PI noted above, the alarmists are minority when it comes to SLR and the consensus is that SLR will be fairly slow. On the question of CO2 sensitivity there are a few recent papers suggesting lower sensitivity and acknowledging that the climate models exaggerate warming.

[On Guard for Thee]

Not really. It really depends on the topic. For example, when it come to the question of the impact of climate change on extreme weather events the alarmists are a minority. The scientific consensus is there is no evidence of any impact, however, it is possible that the impact will be observable in the future but only if you believe the climate models are not exaggerating. Also, as PI noted above, the alarmists are minority when it comes to SLR and the consensus is that SLR will be fairly slow. On the question of CO2 sensitivity there are a few recent papers suggesting lower sensitivity and acknowledging that the climate models exaggerate warming.

Sounds like pretty well cherry picked science and wishful thinking to me. Alarmists as you like to call them are far from a minority if you want anything professionally peer reviewed.

[TimG]

Sounds like pretty well cherry picked science and wishful thinking to me. Alarmists as you like to call them are far from a minority if you want anything professionally peer reviewed.

I am talking about peer reviewed stuff. And if you don't understand that the degree of consensus depends on the exact topic then you clearly know nothing useful about this topic. Edited April 2, 2015 by TimG

[-1=e^ipi]

But its not uncommon that people attempt to ignore sources that oppose their ideas. Its quite common actually.

You mean like how alarmists do ALL the time. Yeah, it is very common.

On the question on what the IPCC's position on expected sea level rise over the next century, I referenced chapter 13 of the IPCC's AR5 report (which is on sea level rise). How is that trumped by some journalist reporting on the IPCC report? I referenced the source directly.

seem to make up the ever growing majority of the peer reviewed studies. maybe its telling us we ought to get a bit alarmed.

Confirmation bias and appeal to authority fallacy.

[On Guard for Thee]

You mean like how alarmists do ALL the time. Yeah, it is very common.

On the question on what the IPCC's position on expected sea level rise over the next century, I referenced chapter 13 of the IPCC's AR5 report (which is on sea level rise). How is that trumped by some journalist reporting on the IPCC report? I referenced the source directly.

Confirmation bias and appeal to authority fallacy.

The IPCC report quite clearly states it does not take into consideration any increase to their estimates, which are based primarily on thermal expansion, for any increase due to dynamic ice sheet response. There are other reports which do consider the increasing rapidity of ice sheet melt which puts th numbers higher. And thats not considering any major slippage of any sheets, simply the melt.

[-1=e^ipi]

After reading Steve McIntyre's criticisms of some of Mann reconstructions, I see Tim's point about it being a lot less reliable than it appears.

Any issue with Shakun and Carlson 2010?

[GostHacked]

And that time is shrinking as we warm the place up. Its funny you quote the IPCC, I thought you naysayers tried to pooh pooh their stuff. But if you go that route than you should know their latest report has SL rise at between 1 and 13 feet by end 2100. Your little beaver dam picture is cute of course, but those little guys are dealing with a regular seasonal flow. Not a series of floods followed by drought.

Between 1 and 13 feet? Are people forgetting that the tectonic plates move causing some shorelines to increase, and others to decrease?

[On Guard for Thee]

Between 1 and 13 feet? Are people forgetting that the tectonic plates move causing some shorelines to increase, and others to decrease?

Sure, but thermal expansion and glacial and ice sheet melt only cause SL increase.

[GostHacked]

Sure, but thermal expansion and glacial and ice sheet melt only cause SL increase.

Ice takes up more volume than water. Frozen water expands. Do people not know this?

[On Guard for Thee]

Ice takes up more volume than water. Frozen water expands. Do people not know this?

Im sure they do. Especially anyone who has had a water pipe burst in the winter. Not quite sure how that applies to SL rise though.

[GostHacked]

Im sure they do. Especially anyone who has had a water pipe burst in the winter. Not quite sure how that applies to SL rise though.

Think of the ocean as a big glass. and the ice caps as ice cubes ... yes, very difficult to wrap one's brain around.

[On Guard for Thee]

Think of the ocean as a big glass. and the ice caps as ice cubes ... yes, very difficult to wrap one's brain around.

The problem with the antarctic ice cap and the glaciers as they arent in the glass, but when they melt and run into the glass, the glass overflows. Does that help you.

[-1=e^ipi]

Ice takes up more volume than water. Frozen water expands. Do people not know this?

Ghost Hacked,

1 Plate techtonics are too slow to be relevant over any time scale less than a million years.

2. With respect to your comments on ice. Ice does have a larger volume, but as a result it has a smaller density. As a result, it floats on top of water and not all of the volume of ice will displace water, some of ice will displace air instead. About 90% of an iceberg is under water for example. As a result, melting of sea ice has no significant impact on sea level. Melting of continental ice sheets such as Greenland and Antarctica do have a significant impact on sea level however.

[-1=e^ipi]

Any issue with Shakun and Carlson 2010?

Looks like even Shakun and Carlson's claim of ~4.9 C difference between Last Glacial Minimum and Holocene Optimum is disputed as well. Schmittner et al. 2011 use Shakun and Carlson's data plus additional data (they uses 435 grid points vs the 54 of Shakun and Carlson) and obtain a best estimate of the Last Glacial Minimum-Holocene Optimum of ~3.0 C. Schmittner defends his/her study in the comment section of this blog:

http://www.skepticalscience.com/news.php?p=1&t=77&&n=1140

But even Schmittner 2011 seems to be disupted.

[TimG]

Looks like even Shakun and Carlson's claim of ~4.9 C difference between Last Glacial Minimum and Holocene Optimum is disputed as well.

Skeptical Science is a propaganda site that trashes all papers that cast doubt on the consensus and mindlessly defends pro-consensus papers even when the flaws are painfully evidence. If you want to understand the bias of this site read some of its coverage of Mann's papers. You should find any number of absurd claims dressed up with pseudo-scientific lingo to make them *sound* credible but are nonsense if you understand the nature of the flaws in Mann's work. Personally, if Skeptical Science trashes a paper I would flag it as worth learning more about (sometimes they trash papers because they deserve it but most of the time it is just because the paper does not adhere to the AGW cult credo). Edited April 8, 2015 by TimG

[-1=e^ipi]

There was a similar thread on Real Climate. Also, Judith Curry had a guest post on her blog with different criticisms.

http://judithcurry.com/2011/11/29/wht-on-schmittner-et-al-on-climate-sensitivity/

But yes, I am aware of the bias at skeptical science.

[-1=e^ipi]

Okay, I've looked more into it. Schmittner, being a good scientist, recognizes the potential for biased results in Schmittner et al. 2011.

http://cicar.ei.columbia.edu/sitefiles/file/Schmittner-sensitivity.pdf

Fortunately, it seems that Annan & Hargreaves 2013 have tried to resolve this issue and get an accurate, empirical estimate of the temperature change from the last glacial maximum to the Holocene optimum.

http://www.clim-past.net/9/367/2013/cp-9-367-2013.html

So it looks like the 95% confidence interval for cooling since the last glacial maximum is 4.0 +/- 0.8 C.

Maybe I can use this + ice core data to get a decent estimate of the impulse response function by using the Van Hateren approach.

[-1=e^ipi]

So I tried estimating a Van Hateren impulse response function from the Pleistocene ice core data. I used dome C data for the past 800,000 years. I multiplied the temperature data by 0.4 to get a proxy of global temperature (a factor of 0.4 is justified by the results of Annan & Hargreaves 2013).

ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/epica_domec/edc3deuttemp2007.txt

ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/antarctica2015co2.xls

ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/epica_domec/edc-ch4-2008.txt
ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/epica_domec/edc-n2o-2010-800k.txt

The N2O data has a few gaps in the data set. So N2O was regressed as a function of CO2 and CH4, and the CO2 and CH4 data was used as a proxy for N2O (CO2 and CH4 were linearly interpolated to get CO2 and CH4 values for the same years as the N2O data; a linear interpolation was chosen because a higher order interpolation such as a cubic interpolation can behave weirdly if used on a noisy data set unless an arbitrary smoothing parameter is chosen). Greenhouse gas forcing was calculated for each year with either CO2 or CH4 data (the other value being obtained via linear interpolation).

Milankovitch data over the past 800,000 years was also obtained.

http://biocycle.atmos.colostate.edu/shiny/Milankovitch/

Mean Annual Solar Irradiance was approximated as 1365.39 W/m^2 times sqrt((1 - 0.0167^2)/(1 - e^2)), where e is the eccentricity of the Earth for a given year. The 1365.39 W/m^2 value was used since it is the average solar irradiance for the past 9400 years according to Steinhilber 2011 (Solar Irradiance estimations aren't really available prior to the Holocene).

In addition to Mean Annual Solar Irradiance, two other Milankovitch indices were calculated (sin(o)/(1 - e^2) and -e*sin(o)*sin(p)), where o is obliquity and p is precession. These factors help take into account the spatial and temporal distribution of sunlight across the globe over the Pleistocene.

For the model used, it uses a Van Hateren impulse response function with decay times varying from 32 years to 2048 years (32 was chosen because the data isn't temporally resolved enough to do anything smaller and 2048 was chosen since it is more than big enough to account for even the slowest feedbacks such as the ice-albedo feedback). The mathematical model I use is a bit simpler since I treat each temperature observation as a single data point rather than a mean over a time period. Another thing I do is I treat forcing over time to be the linear interpolation of my GHG and Milankovitch data (rather than as a step function). You guys don't seem to like the details, so I will skip them.

Note that since the data covers a longer period of time, since my decay times are longer, and since I am not treating slow feedbacks such as the ice-albedo feedback as exogenous, the calculated impulse response function can give me an estimate of the Earth System Sensitivity (ESS). My 95% confidence interval of the ESS is [2.0, 17.0] C with a median estimate of 5.8 C (but this confidence interval doesn't take into account the uncertainty on my choice of the 0.4 factor).

However, the ESS is unlikely to be constant over the Pleistocene. The ice-albedo feedback is much stronger in the middle of an ice age when glaciers are located in areas that have more direct sunlight than it is during an interglacial. If I try to allow for the ESS to vary with temperature, my median estimate of ESS (at pre-industrial temperatures) drops to ~ 5 C, but the uncertainty increases significantly due to specification error.

Maybe I should use sea-level reconstruction data as a proxy for the slow feedbacks (ice-albedo, sea level rise, vegetation) and use that as a forcing parameter in my model. This would cause the impulse response function to estimate the equilibrium climate sensitivity (ECS) rather than the ESS. This could have an advantage if the ECS is approximately constant with temperature where as the ESS decreases with temperature. Though I would then have the look at the response of sea level to changes in the other forcing parameters.

Maybe Nic Lewis is correct when he says that not much confidence can be put into Paleoclimate data relative to Instrumental data.

Edited April 11, 2015 by -1=e^ipi

[-1=e^ipi]

I tried adding sea level data as a forcing.

ftp://ftp.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/bintanja2005/bintanja2005.txt

The median estimate of climate sensitivity drops to ~4C, but the certainty gets absurdly large because sea level is strongly correlated with GHG forcing. The other issue is that the bintanja sea level reconstruction arguably has a lot of model specification error and isn't 100% based on empirical data.

I could use something like http://www.highstand.org/erohling/Rohling-papers/Rohling%20et%20al%20Nat%20Geosc_%20data%20supplement.xls, but that only goes back 500,000 years and not the full 800,000.

I don't think adding sea level as an indicator of forcing is a good idea. Overall, it doesn't seem that much confidence can be placed on Pleistocene data compared to the Instrumental data. Even the Holocene data gave more confident results than the Pleistocene data.

[-1=e^ipi]

On the idea that a cooler global climate = drier and more desert like conditions, where as a warmer global climate = wetter and less desert like conditions, I would like to point to the 4.2 kiloyear event, the 5.9 kiloyear event and the 8.2 kiloyear event.

http://en.wikipedia.org/wiki/4.2_kiloyear_event

http://en.wikipedia.org/wiki/5.9_kiloyear_event

http://en.wikipedia.org/wiki/8.2_kiloyear_event

In all 3 cases, global cooling, specifically in the North Atlantic, caused increased aridisation of the Sahara, Arabia and elsewhere. This had many detrimental effects on civilizations in those areas.

Also, if you look at the first ancient civilizations (Ancient Egypt, Mesopotamia, Persia, Indus Valley) these places were a lot wetter and less arid during the mid-Holocene. Today, conditions are much drier and these areas are very desert-like. Since the Holocene optimum, eccentricity, precession and obliquity of the Earth's orbit have all changed to make the Earth gradually cooler (without human GHG emissions, Earth would start to go into an ice age in ~1500 years). So perhaps the increased desertification of these areas is due to Milankovitch effects.

[On Guard for Thee]

As global warming continues to rear its ugly head, and California enters its fourth year of severe drought, the locals there are figuring out maybe it would be a good idea to stop watering their lawns so much, especially at midday. The good news is Quebec, Ontario, and California are now joining hands on cap and trade programs. Lets hope its not too late.

[TimG]

As global warming continues to rear its ugly head, and California enters its fourth year of severe drought.

Droughts that California has experienced in the past 1000 years and will experience again.

I think it worth remembering that 10 years ago Australians were so convinced that they had entered a period of endless droughts. Then the drought ended...