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Ken Fabian

Is doubt of climate science the right place to start?

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Swansont,

To further clarify


It is done by some models. But that misses the point.

 

 

Its not just some models and It does miss that point, because I was trying to address your original point in that specific instance, not the models in general. It does clarify your original post on narrow grounds, without extending the clarification to any impact on the merits of the models. Your original post suggesting changing emission scenarios in reality not matching modelled scenarios asa possible explanation for any divergence in recent years between modelled scenarios and surface temperature data.

 

To elaborate

The second source of uncertainty is what mankind is going to do. And we are not going to talk too much about that today. And the solutions on this graph don't really separate out until 2040 or so. Most of the climate change between now and 2040 is committed from historical emissions, about two-thirds of the common signal.

 

The graph relates to the 45 modelled scenarios the IPCC used in its latest report. Page 31.

 

Quote from Dr.Collins, lead author of latest IPCC report on model evaluation. From page 37

http://www.aps.org/policy/statements/upload/climate-seminar-transcript.pdf

 

To clarify, this specific point is only addressing your original post, not the merit of IPCC modelling in general (or ore correctly, their summaries).

Edited by tantalus

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Swansont,

To further clarify

 

 

Its not just some models and It does miss that point, because I was trying to address your original point in that specific instance, not the models in general. It does clarify your original post on narrow grounds, without extending the clarification to any impact on the merits of the models. Your original post suggesting changing emission scenarios in reality not matching modelled scenarios asa possible explanation for any divergence in recent years between modelled scenarios and surface temperature data.

 

My original point has little to do with models; you might notice I didn't use that word in my original post. It has to do with scenarios (the word Brown used), and these aren't the same thing.

 

 

The very first model listed, NorESM1-M, has a scaling factor that's almost exactly 1. So no, not all models.

 

To elaborate

The graph relates to the 45 modelled scenarios the IPCC used in its latest report. Page 31.

 

Quote from Dr.Collins, lead author of latest IPCC report on model evaluation. From page 37

http://www.aps.org/policy/statements/upload/climate-seminar-transcript.pdf

 

To clarify, this specific point is only addressing your original post, not the merit of IPCC modelling in general (or ore correctly, their summaries).

 

 

"The graph"? I specifically pointed out which graph I was looking at (10.4), and it's an analysis of 9 models. This was concerning the discussion around page 265, as you may recall. You appear to be bringing up an entirely different portion of the discussion. And as I've pointed out, it addresses none of my original point since it's an analysis of models, and not scenarios.

 

Short version: it doesn't matter much which of the models you pick, if you have used a scenario with a rise in CO2 of 100% vs the actual rise of 50%, you are going to end up with a larger temperature increase in the former case than in the latter CO2 is a positive forcing, so that's going to be true regardless of the model you pick. But nobody should be surprised by this, and it has no bearing on the accuracy of the models, or the consensus of global warming.

 

 

I don't see where you have defined what level of accuracy you need when you claim that models are inaccurate. How accurate do they need to be?

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I am definitely confused by your post. Also, I am not sure what page 265 refers to (the transcript?)

 

When I discuss scenarios, I'm really refering to how models handle sensitivity, and how that affects their predictions of future temperature rises, perhaps that is confusing others when they read my posts.

 

To quote your original post

But it's meaningless if one doesn't actually assess it. What are the "most severe IPCC projections"? Are we actually in a situation where the world is following that scenario, and yet temperatures are lower than projected? Without looking into that, throwing around quotes as if the mean something is pointless. Because the simplest answer is that we just aren't following the worst-case scenario.

 

My point is that the IPCC latest modelling efforts don't deviate until 2040 with different co2 emission scenarios. Current difficulties in matching recent surface temperatures are not linked to co2 emission scenarios. Obviously nobody will be stating models are wrong 80 years from now if the model in question ran a different co2 emission scenario than actually occurred.

 

 

 

 

I don't see where you have defined what level of accuracy you need when you claim that models are inaccurate. How accurate do they need to be?

Dont really no. IPCC have different modelled scenarios in regard to climate sensitivity, so which ones best fit real data as it comes in? And the state of expert opinion in regard to modelling failures to match real observations, and what, if anything, we can take from that over the short time periods in question.

 

Since we don't know what the temperatures are going to be, the discussion on uncertainties and limitations in the models to account for variables that affect climate sensitivity are very important.

 

The question is there a consensus among experts and what broadly are they disagreeing about and does this have implications in regard to certainty about different projections of climate sensitivity...

Edited by tantalus

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I am definitely confused by your post. Also, I am not sure what page 265 refers to (the transcript?)

Yes, as mentioned in the Watts blog post you linked to. (he says 259-260)

 

When I discuss scenarios, I'm really refering to how models handle sensitivity, and how that affects their predictions of future temperature rises, perhaps that is confusing others when they read my posts.

But that's not what Brown meant, which is clear by the article (or I assume so; I can't get to the sciencedaily page but they just repost stuff anyway) I looked at this:

 

http://www.accuweather.com/en/weather-blogs/climatechange/middleoftheroad-warming-scenar/46028133

 

This clearly shows they are comparing to the A and B family of scenarios. Not models.

 

 

To quote your original post

My point is that the IPCC latest modelling efforts don't deviate until 2040 with different co2 emission scenarios. Current difficulties in matching recent surface temperatures are not linked to co2 emission scenarios. Obviously nobody will be stating models are wrong 80 years from now if the model in question ran a different co2 emission scenario than actually occurred.

But your point has nothing to do with my point, or Brown's quote.

 

Dont really no. IPCC have different modelled scenarios in regard to climate sensitivity, so which ones best fit real data as it comes in? And the state of expert opinion in regard to modelling failures to match real observations, and what, if anything, we can take from that over the short time periods in question.

 

Since we don't know what the temperatures are going to be, the discussion on uncertainties and limitations in the models to account for variables that affect climate sensitivity are very important.

 

The question is there a consensus among experts and what broadly are they disagreeing about and does this have implications in regard to certainty about different projections of climate sensitivity...

So you have no target in mind, which is convenient. NO model is 100% accurate. So even though you agree this is important, having no value in mind gives you leave to take potshots at the efforts and call them inaccurate, but leaves you with no accountability in the discussion at all, because there is no way to be 100% accurate. So even if they end up nailing something to 0.01ºC, you (and others) can still call them inaccurate, even though that level of accuracy is not needed to inform us of what's going to happen.

 

And this has implications about consensus and whether they are broadly agreeing or disagreeing.

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So you have no target in mind, which is convenient. NO model is 100% accurate. So even though you agree this is important, having no value in mind gives you leave to take potshots at the efforts and call them inaccurate, but leaves you with no accountability in the discussion at all, because there is no way to be 100% accurate. So even if they end up nailing something to 0.01ºC, you (and others) can still call them inaccurate, even though that level of accuracy is not needed to inform us of what's going to happen.

 

And this has implications about consensus and whether they are broadly agreeing or disagreeing.

No body expects them to be 100% accurate. I don't have the expertise to give you numbers, I would be wasting your time.

 

In the observations, what factor or factors have contributed to the stasis in tropospheric and surface warming and why are the tropospheric temperature trends in CMIP5 models, on average, larger than those observed over the stasis period?

 

From Page 211 of the transcript, Santers presentation.

 

Now while he is acknowledging the models difficulty, he goes on to propose a series of potential explanations for the stasis and models difficulty, and he doesnt feel they threaten the over all picture, so you can read those in the few pages that follow 211.

 

Curry states that in regard to the hiatus that

Only 2% of climate model simulations produce trends within the observational uncertainty

 

http://judithcurry.com/2014/03/04/causes-and-implications-of-the-pause/

 

 

I don't understand your position, even IPCC scientists like Collins and Santer acknowledge model failures over the last 15 years in regard to the hiatus. The real issue is the significance, if any, of such problems.

 

In addition, since only time can confirm the merits of current modelling, discussions must be had not just in relation to the hiatus, which may not be very significant, but on the theoretical element of the models, and the level of uncertainty within them. The transcripts convey this debate well, although I havent read all of it yet (still need to read Isaac Held and concluding questions/discussion sections).

 

 

But that's not what Brown meant, which is clear by the article (or I assume so; I can't get to the sciencedaily page but they just repost stuff anyway) I looked at this:

 

http://www.accuweather.com/en/weather-blogs/climatechange/middleoftheroad-warming-scenar/46028133

 

This clearly shows they are comparing to the A and B family of scenarios. Not models.

 

But your point has nothing to do with my point, or Brown's quote.

 

No, I am even more confused

Short version: it doesn't matter much which of the models you pick, if you have used a scenario with a rise in CO2 of 100% vs the actual rise of 50%, you are going to end up with a larger temperature increase in the former case than in the latter CO2 is a positive forcing,

 

None of the recent IPCC models deviate in co2 emissions until later into the century, therefore they can't effect the initial point of discussion, the recent hiatus.

 

[mp][/mp]

Ok I think I get one of your points now (I was slow on the uptake), Its actually unclear if Brown discusses solely A and B scenarios, or more at length about IPCC models, I think he is discussing both, although separately. You certainly can't discuss the recent hiatus in terms of scenarios, but actual models, but I think I see your actual point about what Brown is saying in regard to (only specifically in regard to) his "middle of the road" comment and the A, B scenarios.

Edited by tantalus

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The hiatus isn't a lack of warming, just a lower rate of surface temperature warming compared to predictions.what does this mean?

 

1 climate science is BS. Not likely.

 

2 CO2 sensitivity is lower than initially though. Partially true, the upper range has been lowered.

 

3 the heat isn't where it was thought to be. Partially true. We have less information on the oceans, Arctic, and Antarctic compared to continental land mass. Evidence is suggesting that these areas are warming faster than predicted.

 

4 warming isn't a linear shift. Very true. When the record is updated to include data up to and including 2015, the hottest year on record, the hiatus all but disappears. Give it a few more years, and I suspect we will have to reconsider CO2 sensitivity upwards as more data comes in.

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Ok I think I get one of your points now (I was slow on the uptake), Its actually unclear if Brown discusses solely A and B scenarios, or more at length about IPCC models, I think he is discussing both, although separately. You certainly can't discuss the recent hiatus in terms of scenarios, but actual models, but I think I see your actual point about what Brown is saying in regard to (only specifically in regard to) his "middle of the road" comment and the A, B scenarios.

 

I don't think that's so. What he's implying is if the worst case scenarios had held, we wouldn't have had this so-called hiatus for the length of time we saw.

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I don't think that's so. What he's implying is if the worst case scenarios had held, we wouldn't have had this so-called hiatus for the length of time we saw.

Yes, I would agree on that's what he is saying.

Edited by tantalus

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Yes, I would agree on that's what he is saying.

 

So how does that call into question the consensus on warming? We know we're in a middle-of-the-road scenario, and we see warming — none of that is challenged by what was said. The question is about how severe it will be, and how accurately we need to predict that. But you won't/can't constructively engage on that.

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So how does that call into question the consensus on warming? We know we're in a middle-of-the-road scenario, and we see warming — none of that is challenged by what was said. The question is about how severe it will be, and how accurately we need to predict that. But you won't/can't constructively engage on that.

I misused the Brown paper, so it has little impact on a consensus on warming from what I think you mean by that.

 

Please note that its not a consensus on warming that is in question, well I suppose for the last 15 years there clearly is debate as underestimated volcanic aerosols or natural variability linked to long term climate cycles not included in models, or heat storage, or problems with model sensitivity et al. may be offsetting co2 increases, but long term we should absolutely see warming, the question is how much. And if the IPCC conveys the state of the science and certainty when they represent the modelling results they collate, actually more that do they convey the state of their own collected science in their summaries.

 

This is achieved in part by reasoning the evidence, for example expert judgement of the uncertainties in modelling results, not just looking at the graphs of actual models and their error bars. Those kinds of uncertainties in the models are absurdly complicated to a layperson, you can only yield to expert opinion. I don't think IPCC summaries are an accurate reflection based on the views of others.

 

I have tried to present on the this idea of an extension of the consensus that extends through to confidence in the IPCC models as reflected in their summary.

Edited by tantalus

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Tantalus, if you won't accept that climate modelling is a valid way to figure the possible and likely consequence of emissions, how do you think we should make some kind of judgement and proceed?

 

From my perspective I see pretty much every major study or report, from every institution that studies climate, every peak science body and every Academy of Sciences saying it's real, it's serious and it's urgent. There are also a lot of uncertainties that are not, in my view, glossed over. They include the possibility that impacts may be less severe than some kind of average of models and projections. But I think uncertainty leaves open the possibility that they may be much more severe.

 

Taking no actions until we know better is in reality continuing to take strong actions - gigatonnes a year of fossil fuel burning - on the basis that we just don't know. Yet claiming we just don't know looks like a choice, one that involves withholding acceptance of the validity of the body of knowledge science has accumulated so far. For those not working professionally it's a free choice; only those bound by professional codes of conduct have any obligations that preclude believing and saying whatever they want.

 

To what extent should your personal doubts be grounds for withholding acceptance of the professional work of others - work that National Academies and Meteorological organistions consider valid? And to what extent should that withheld acceptance be the basis in turn of political opposition to policy that treats the mainstream advice as valid?

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Tantalus, if you won't accept that climate modelling is a valid way to figure the possible and likely consequence of emissions,

No, climate modelling is a valid scientific method. The way the IPCC portray that body of work and the state of that science in their summaries is when much of the problem emerges.

 

how do you think we should make some kind of judgement and proceed?....

 

....Taking no actions until we know better is in reality continuing to take strong actions - gigatonnes a year of fossil fuel burning - on the basis that we just don't know.

First, it's a logically sound principle to take preemptive action without certainty.

 

Assessing action is very complicated and requires the input of scientists, economists, politicians from a wide range of fields, and their findings will vary locally and regionally. We should assume that the specific outcomes of their work are significantly effected depending on the amount of warming that occurs or our assessment of such certainty, and or the perception that takes hold from the IPCC reports.

 

In light of such a complex process, I will give you a tepid response and it should be judged as such, not in absolutes.

 

It's also worth noting that certain measures have other reasons to be undertaken anyway, consider the problems the Chinese face with air pollution relating to coal, even without factoring in their carbon emissions.

 

I think we should focus on carbon-emission efficient technologies, climate adaption, especially in poorer countries, correct a mistake I think we made decades ago, and refocus on nuclear (especially over coal), while resisting calls for rapid reductions in carbon emissions that would damage growth, or the employment of expensive carbon sequestration proposals.

 

Climate adaption is the key and a sound investment, needs to be applied at a local and regional level and possess many benefits other than to counter man made climate change effects. In fact, they would also protect against natural climate change, decadal variability, extreme weather events. And align with many other solutions to other environmental problems such as flood plain management, habitat loss, soil erosion etc

 

A particular focus will be needed on global food security and preventing fluctuations in key commodities prices. The free-market is very sensitive and there is potential of quickly seeing millions being unable to afford food, and many rapidly sliding back into poverty.

 

 

To what extent should your personal doubts be grounds for withholding acceptance of the professional work of others - work that National Academies and Meteorological organistions consider valid? And to what extent should that withheld acceptance be the basis in turn of political opposition to policy that treats the mainstream advice as valid?

I find the second last question is oddly framed, nobody should be including someone like me in a framework for policy formation, but that's not to say my opinions shouldn't be included.

 

On your last question, naturally I feel my opinions have a sound basis and should be included in political opposition as necessary.

 

There is something worth mentioning not related to policy, the conduct of science. I feel that the scientific process is being damaged. Since advocating policy is needed in some form, and funding is required, there is an unavoidable link between politics and science.

 

However the language of politics has rapidly crossed back into the field of science, any debate of IPCC work now is often being shot down with political language, and this is not in the spirit of the scientific process.

Edited by tantalus

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What about all of the other species that cannot adapt? Do we not have an obligation to take all life on earth into account, not just us?

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What about all of the other species that cannot adapt? Do we not have an obligation to take all life on earth into account, not just us?

Or, put another way, how do we adapt to the loss of the species that we lose? I suspect predicting the details of that is a much, much harder problem than predicting the temperature change.

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What about all of the other species that cannot adapt? Do we not have an obligation to take all life on earth into account, not just us?

Depends on your value system, the intrinsic value of non-sentient life is a tough sell to many. Species and ecosystems have monetary values that are dramatically underestimated by the free market, an economic and functional based argument is a more productive avenue imo.

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Depends on your value system, the intrinsic value of non-sentient life is a tough sell to many. Species and ecosystems have monetary values that are dramatically underestimated by the free market, an economic and functional based argument is a more productive avenue imo.

 

As research progresses, sentience is not limited to humans.

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As research progresses, sentience is not limited to humans.

For sure, but big picture, not relevant to most species on the planet

[mp][/mp]

Or, put another way, how do we adapt to the loss of the species that we lose? I suspect predicting the details of that is a much, much harder problem than predicting the temperature change.

Here's the thing about species extinction, there are usually multiple drivers. So when a species goes extinct, do we blame climate, habitat loss, pollution, alien competitor out competes native etc. There is very little evidence for extinctions linked to climate change being key so far, a handful, but not many. That said, they are going to be difficult to prove neatly when they do happen moving forward.

 

In the past, even with abrupt climate change, many species could change their ranges quickly and survive, these days many of those species will try to move to find their new suitable real estate climatically is cereal farmland or suburbia. Screwed. Incidentally, this is one of the greatest challenges to the currently popular idea of ring-fencing large areas of land to preserve species. Inevitably the climate will change and when they can't move...

 

Furthermore many of those species may be vulnerable and endangered already requiring only a small shock to tip them over. And this surely is the reality.

 

It's surely the case that many species are really heading for extinction already, due to loss of genetic pool, but they havent gotten over the line yet.

 

Another thing is that measuring the problem by species number has fundamental limitations., you could prevent a species extinction but another species or element of their environment goes and it can set off a cascade that leads to ecosystem collapse. Also, important to thing in terms of genetic loss, not just because you need a healthy gene pool to ensure long term survival of a species for breeding, but also in terms of adaptability to environmental changes. Furthermore, a value of a species is often thought in terms of the potential compounds that can be developed from it for producing new medical treatments and drugs, a species is lost, and the cure to cancer could go with it etc, well not just a species, a particular population, genetically unique, of that species could go silently extinct, and of course its a far more common phenomena than species extinction.

 

All that said, the key problem is habitat loss, if we are serious about preventing extinction , that's were we will start, climate change will interact with that main driver to finish many species off, but if we don't tackle habitat loss we should expect the current dramatic extinction rate to continue.

 

In terms of adapting to the loss, in part you can't know what you never had, I think we will continue on being largely ignorant of it, as we have been doing for a long time, and reaping the benefits of new technology and improving living standards, even though we could have done far better.

 

Eventually with peak population, and new technology, we should be able to turn the tide, but I feel the species of the world will feel the problem far more than human society.

 

 

Edited by tantalus

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Here's the thing about species extinction, there are usually multiple drivers. So when a species goes extinct, do we blame climate, habitat loss, pollution, alien competitor out competes native etc. There is very little evidence for extinctions linked to climate change being key so far, a handful, but not many. That said, they are going to be difficult to prove neatly when they do happen moving forward.

 

I don't find the excuse of "it might not have been climate change" to be very compelling. Fracking a species to death (as an example) is not any kind of improvement.

 

And to use "so far" as a benchmark, I'll just ask — is there anyone out there making the case that it's going to get better?

 

In the past, even with abrupt climate change, many species could change their ranges quickly and survive, these days many of those species will try to move to find their new suitable real estate climatically is cereal farmland or suburbia. Screwed. Incidentally, this is one of the greatest challenges to the currently popular idea of ring-fencing large areas of land to preserve species. Inevitably the climate will change and when they can't move...

And of course you can point to previous instances of climate change as abrupt as this.

 

No?

 

Then that's a moot point.

 

Furthermore many of those species may be vulnerable and endangered already requiring only a small shock to tip them over. And this surely is the reality.

Why are they already endangered, though? This sounds like "we've already screwed them most of the way. Why not finish the job?"

 

It's surely the case that many species are really heading for extinction already, due to loss of genetic pool, but they havent gotten over the line yet.

 

Another thing is that measuring the problem by species number has fundamental limitations., you could prevent a species extinction but another species or element of their environment goes and it can set off a cascade that leads to ecosystem collapse. Also, important to thing in terms of genetic loss, not just because you need a healthy gene pool to ensure long term survival of a species for breeding, but also in terms of adaptability to environmental changes. Furthermore, a value of a species is often thought in terms of the potential compounds that can be developed from it for producing new medical treatments and drugs, a species is lost, and the cure to cancer could go with it etc, well not just a species, a particular population, genetically unique, of that species could go silently extinct, and of course its a far more common phenomena than species extinction.

 

All that said, the key problem is habitat loss, if we are serious about preventing extinction , that's were we will start, climate change will interact with that main driver to finish many species off, but if we don't tackle habitat loss we should expect the current dramatic extinction rate to continue.

People are already concerned with habitat loss. That's an issue of political will. But there's probably a pretty good overlap of people who don't care about habitat preservation and those who sit on their hands when global warming is the action item.

 

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I don't find the excuse of "it might not have been climate change" to be very compelling. Fracking a species to death (as an example) is not any kind of improvement.

 

And to use "so far" as a benchmark, I'll just ask — is there anyone out there making the case that it's going to get better?

 

 

No i doubt it. But basically what I am saying is climate change is linked to only a handful of extinctions in the last 100 years, extraordinary high extinctions rates have been driven by other players and we are likely to see the continuation of that pattern.

 

And of course you can point to previous instances of climate change as abrupt as this.

 

No?

 

Then that's a moot point.

 

Abrupt is a relative term. Regionally you can look at the medieval optimuum 950-1100 and the little ice age, cool periods in the 1600, 1700 and 1800s punctuated by warming periods.

 

Dramatic abrupt changes have occured regularly (over 20) over the last 100,000 years with events where proxy records indicate 5, 10 degree jumps in years and decade time periods.

 

One example is the youner dryas, a 2-6 degree celsius drop in northern latitudes in decades.

https://en.wikipedia.org/wiki/Younger_Dryas

 

These events are not punctuated by rates of extinction that we are currently witnessing.

 

 

Why are they already endangered, though? This sounds like "we've already screwed them most of the way. Why not finish the job?"

 

No, was pointing out that climate change is likely to be more important that in the past because species are so vulnerable.

 

 

People are already concerned with habitat loss. That's an issue of political will. But there's probably a pretty good overlap of people who don't care about habitat preservation and those who sit on their hands when global warming is the action item.

 

It's more than political will, there is a fundamental problem with increasing world population and seeking to raise living standards for everyone and still wanting to preserve the habitat, but I take your point.

Edited by tantalus

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Dramatic abrupt changes have occured regularly (over 20) over the last 100,000 years with events where proxy records indicate 5, 10 degree jumps in years and decade time periods.

 

One example is the youner dryas, a 2-6 degree celsius drop in northern latitudes in decades.

https://en.wikipedia.org/wiki/Younger_Dryas

Northern latitudes. Younger Dryas was not global.

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Northern latitudes. Younger Dryas was not global.

In western Europe and Greenland, the Younger Dryas is a well-defined synchronous cool period.[34] But cooling in the tropical North Atlantic may have preceded this by a few hundred years; South America shows a less well defined initiation but a sharp termination. The Antarctic Cold Reversal appears to have started a thousand years before the Younger Dryas, and has no clearly defined start or end; Peter Huybers has argued that there is fair confidence in the absence of the Younger Dryas in Antarctica, New Zealandand parts of Oceania.[35] Timing of the tropical counterpart to the Younger Dryas – the Deglaciation Climate Reversal (DCR) – is difficult to establish as low latitude ice core records generally lack independent dating over this interval. An example of this is the Sajama ice core (Bolivia), for which the timing of the DCR has been pinned to that of the GISP2 ice core record (central Greenland). Climatic change in the central Andes during the DCR, however, was significant and characterized by a shift to much wetter, and likely colder, conditions.[36] The magnitude and abruptness of these changes would suggest that low latitude climate did not respond passively during the YD/DCR.

 

 

https://en.wikipedia.org/wiki/Younger_Dryas

With such dramatic changes in northern latitudes we can expect global effects. Cooler, warmer, wetter, drier, it all has effects on species locally adapted to past conditions.

 

Furthermore at a local and regional level a species can't make a distinction.

 

Ocean and lake sediment data from places such as California, Venezuela, and Antarctica have confirmed that these sudden climate changes affected not just Greenland, but the entire world. During the past 110,000 years, there have been at least 20 such abrupt climate changes. Only one period of stable climate has existed during the past 110,000 years--the 11,000 years of modern climate (the "Holocene" era). "Normal" climate for Earth is the climate of sudden extreme jumps--like a light switch flicking on and off.

 

http://www.wunderground.com/resources/climate/abruptclimate.asp?MR=1

 

These climate events have not been able to match mankind in the 20th century for causing extinction despite their scale and rapid onset.

 

[mp][/mp]

In fact, some argue that there havnt been extinction rates witnessed on earth since the cretaceous extinction event.

 

Also to add to my previous post, we should expect a bias to reported effects to major climate events to regions that have ice cores as they make such a good proxy for recording shifts in climate.

Edited by tantalus

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http://www.wundergro...limate.asp?MR=1

These climate events have not been able to match mankind in the 20th century for causing extinction despite their scale and rapid onset.

If you read your link there carefully, you will find that the dramatic effects described were large and sudden only locally - in the North Atlantic near Greenland. Although there were measurable global effects from that, they were much smaller and slower.

The current AGW is global, very rapid, and essentially permanent - long term, for sure. No one has discovered a geological precedent for such a warming as we face now. At the same time, the resources and capabilities of wild animals have been much reduced by human usurption -they have much less room to move, fewer options for response.

Edited by overtone

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Furthermore at a local and regional level a species can't make a distinction.

But there are fewer species confined to just those regions, so of course extinction events would be reduced as opposed to global events.

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If you read your link there carefully, you will find that the dramatic effects described were large and sudden only locally - in the North Atlantic near Greenland. Although there were measurable global effects from that, they were much smaller and slower.

Your being selective. The ice cores are in greenland, so the best data will be there, while the greatest changes were there doesnt mean in wasnt very large elsewhere. edit. You will always get dramatic regional differences with climate change, if the IPCC more severe predictions are correct, we should expect more dramatic shift in certain regions over others.

 

Might the change have been restricted to parts of the world near Greenland? The first hints of the answer came from oceanographers, who had been hunting out seabed zones where bioturbation by burrowing worms did not smear any record of rapid change. In some places the sediments accumulated very rapidly, while in others, the sea water lacked enough oxygen to sustain life. The first results, from the Norwegian Sea in 1992, confirmed that the abrupt changes seen in Greenland ice cores were not confined to Greenland alone. Later work on seabed cores from the California coast to the Arabian Sea, and on chemical changes recorded in cave stalagmites from Switzerland to China, confirmed that the oscillations found in the Greenland ice had been felt throughout the Northern Hemisphere. Changes in dustiness were meanwhile noted in the ice itself, indicating at least continental scope for the change; later, a hemisphere-wide Younger Dryas temperature step in less than a decade was confirmed by a step change in the methane gas in the ice.(57) Meanwhile, in the late 1980s and early 1990s, improved carbon-14 techniques gave the first accurate dates for sediments containing pollen and other carbon-bearing materials at locations ranging from Japan to Tierra del Fuego. Good dates finally allowed correlation of many geological records with the Greenland ice. The results suggested that the Younger Dryas events had affected climates, one way or another, around the world. The extent and nature of the perturbation was controversial. But scientists were increasingly persuaded that abrupt climate shifts could have global scope, even if they affected different places differently — colder here and warmer there, wetter here and drier there.

 

https://www.aip.org/history/climate/rapid.htm

 

The Europeans and Americans nevertheless agreed that through most of the last 100,000 years the global climate had oscillated "on a scale that human cultural and industrial activities have not yet faced."

 

Same article.

 

This the the main report you'll fing on abrupt climate change with a case study on the younger dryas

http://www.nap.edu/read/10136/chapter/4#27

 

Beginning immediately after the main warming in Greenland (by less than or equal to 30 years), methane rose by 50 percent over about a century; this increase included tropical and high-latitude sources
Ice cores from other sites, including Baffin Island, Canada (Fisher et al., 1995), Huascaran, Peru (Thompson et al., 1995), and Sajama, Bolivia (Thompson et al., 1998), show evidence of a late-glacial reversal that is probably the Younger Dryas although the age control for these cores is not as accurate as for cores from the large ice sheets.

 

The ice-core records demonstrate that much of the earth was affected simultaneously by the Younger Dryas, typically with cold, dry, windy con-ditions. However, those records do not provide much spatial detail, nor do they sample the whole earth. For those, one must consider a global array of data sources of various types, as described in the following subsections.
The Younger Dryas was first discovered by studying the biological records found in terrestrial sediments. These records clearly reveal the global reach of the event. Owing to dating uncertainties, including those associated with the conversion of radiocarbon measurements to calendar years, the phasing of events between different locations is not known exactly. The ice cores show that much of the world must have changed nearly simultaneously to yield the observed changes in methane, Asian dust, and Greenland conditions, but we cannot say with confidence whether all events were simultaneous or some were sequential.

See link for northern hemisphere pollen evidence of change in ecosystems and species shifts. Also see link for far greater coverage of proxy evidence of the younger dryas event than I present.

Marine evidence of the Younger Dryas event is recorded as an interval of increased upwelling or decreased riverine runoff from adjacent South American land in a core from the Cariaco Basin in the Caribbean (Hughen et al., 1996, 2000a,b; Peterson et al., 2000) (Figure 2.4). Terrestrial evidence is primarily from three sites (Leyden, 1995). Evidence indicates a temperature decline of 1.5-2.5°C during deglaciation, probably correlated with the Younger Dryas,
Alley and Clark (1999) reviewed evidence from several marine cores that show warmth during the Younger Dyras in the southern Atlantic and Indian Oceans, opposite to most global anomalies but consistent with the warmth indicated in most Antarctic ice cores at that time
Overall, the available data indicate that the Younger Dryas was a strong event with a global footprint. Available data are not sufficient to identify the climate anomaly everywhere, and further understanding almost certainly will require more data. Different paleoclimatic recorders respond to different aspects of the climate system with different time resolution, so it is not surprising that the picture is not perfectly clear. Broadly, however, the Younger Dryas was a cold, dry, and windy time in much of the world although with locally wetter regions probably linked to storm-track shifts. The far southern Atlantic and many regions downwind in the southern Indian Ocean and Antarctica were warm during the Younger Dryas. Changes probably were largest around the North Atlantic and probably included reduced export of North Atlantic deep water. Changes into and especially out of the event were very rapid.

 

. At the same time, the resources and capabilities of wild animals have been much reduced by human usurption -they have much less room to move, fewer options for response.

I agree with this in principle

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But there are fewer species confined to just those regions, so of course extinction events would be reduced as opposed to global events.

Hopefully now I have illustrated it was much more than that.

 

You will find a lot discussion that younger dryas was linked to megafaunal extinction especially in north america, I don't find this overly compelling( as a key driver) for a variety of reasons that I rather not get into at length, but suffice to say it it has its advocates in the literature and it has to be given serious consideration.

 

Either way, there is no comparison with current extinction rates.

Edited by tantalus

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