Climate Change Banter

[ORH_wxman]

There are times when you need to throw out whatever your college professor has taught you over the years, and look at things full scope.

Or whoever (or whatever) sources you allow yourself to be guided by.

A site nobody's heard of before. I wonder if they've accepted donations over the years.

So in other words, you are advocating ignoring the scientific method.

[blizzard1024]

^ (in a sense)

 

Given we are entering a new climate era, everything from now on is pretty much causative of a different background state. Even if it happens to be like it was in the 20th century, it will still arrive differently.

 

I am disappointed because climate change is perfectly wired to beat us across the board.

 

All because of a little extra forcing ~ 2W/m2? The outgoing IR at the TOA of ~ 240 W/m2. We have increased only .8C since the 1800s. Plus the Earth was warmer than present in the past 10,000 years and colder than present. So not much really has changed meteorologically speaking. One thing a warmer world would do would be to reduce the temperature gradient between the poles the tropics lessening the severity of mid-latitude cyclones. However, by increasing surface temperatures you increase low-level water vapor and instability in general. This would have the effect of reducing the size of storms on the horizontal scale. This is called the Rossby Radius of deformation which would get smaller and you would indeed see more intense vertical motions and hence more intense precipitation. This is the study that ORH mentioned.

 

However, if you look closely at that study they began the time period in 1958 and ended in it in 2011 a very wet year. I am not sure what the significance is of 1958, maybe that is when we started recorded hourly precipitation rates?? BUT in the 1960s were very dry in much of the northeast especially and this is where the signal was the strongest with more extreme rain events. So it is very possible we are comparing  rain rates from a known dry time to a period that certainly has been wet. I am not saying the authors are cherry picking. I actually am friends with one of them. I am sure they have a good reason to start in 1958 but that could be skewing the data since the 1960s were dry. I would like to see this over a longer period of time.

 

Speaking of floods, more flash floods would certainly be possible if the above study is indeed true. But river floods may drop since warmer temperatures lead to more evaporation and summer drying. Also snow cover melting is a major source of spring river flooding as well and this will also drop so if we did warm up significantly we may see less river floods but more flash flood type scenarios. Of course this says nothing about coastal flooding....

[FloridaJohn]

I believe it will cause about a 1C increase at best.

 

We have increased only .8C since the 1800s.

 

So you believe we only have about 0.2C of warming left to go? So in a couple decades global temperatures will level out, even though we continue to pump CO2 into the atmosphere?

[AvantHiatus]

All because of a little extra forcing ~ 2W/m2? The outgoing IR at the TOA of ~ 240 W/m2. We have increased only .8C since the 1800s. Plus the Earth was warmer than present in the past 10,000 years and colder than present. So not much really has changed meteorologically speaking. One thing a warmer world would do would be to reduce the temperature gradient between the poles the tropics lessening the severity of mid-latitude cyclones. However, by increasing surface temperatures you increase low-level water vapor and instability in general. This would have the effect of reducing the size of storms on the horizontal scale. This is called the Rossby Radius of deformation which would get smaller and you would indeed see more intense vertical motions and hence more intense precipitation. This is the study that ORH mentioned.

 

However, if you look closely at that study they began the time period in 1958 and ended in it in 2011 a very wet year. I am not sure what the significance is of 1958, maybe that is when we started recorded hourly precipitation rates?? BUT in the 1960s were very dry in much of the northeast especially and this is where the signal was the strongest with more extreme rain events. So it is very possible we are comparing  rain rates from a known dry time to a period that certainly has been wet. I am not saying the authors are cherry picking. I actually am friends with one of them. I am sure they have a good reason to start in 1958 but that could be skewing the data since the 1960s were dry. I would like to see this over a longer period of time.

 

Speaking of floods, more flash floods would certainly be possible if the above study is indeed true. But river floods may drop since warmer temperatures lead to more evaporation and summer drying. Also snow cover melting is a major source of spring river flooding as well and this will also drop so if we did warm up significantly we may see less river floods but more flash flood type scenarios. Of course this says nothing about coastal flooding....

What if you include cooling from meltwater feedbacks? In the most extreme scenario, sections of Antarctica and Greenland become colder than the 20th century average, creating insane gradients.

[ORH_wxman]

What if you include cooling from meltwater feedbacks? In the most extreme scenario, sections of Anarctica and Greenland become colder than the 20th century average, creating insane gradients.

 

 

I've never heard of Greenland and Antarctica becoming colder than the 20th century average in a warming world...if that ends up being true, then we don't have to worry about any dangerous sea level rise.

[blizzard1024]

So you believe we only have about 0.2C of warming left to go? So in a couple decades global temperatures will level out, even though we continue to pump CO2 into the atmosphere?

 

At least half of that warming occurred before CO2 levels had increased significantly. We were just rebounding from the Little Ice Age. It is very possible that CO2 only accounts for a small portion of that warming. Additionally, I am not so sure we even have warmed that much. How well did we measure global temperatures in the late 1800s vs Today?? apples to oranges. For the sake of argument if we warmed only .8C it is within the realm of natural variations in the Holocene and I doubt it would cause any major disruption of weather systems. I have been forecasting the weather for 25 years and things don't seem that different. what is different is how the media now reports on weather front and center 24/7. so the perception is that there is more severe storms....

[StudentOfClimatology]

You are underestimating the importance of condensation vs evaporation. Here is a plot of current mean annual temperature vs isotope ratio for samples collected at different locations in Antarctica and Greenland. Note the Antarctic data is Deuterium and Greenland is O18. There is a very good correlation between isotope ratio in current snow samples and the local mean annual temperature. O18 is removed preferentially over the lowest and warmest portions of the ice sheet so by the time water vapor reaches the highest and coldest locations it has been significantly depleted in O18.

That's just because Arctic temperatures tend to track in line with northern hemispheric temperatures. There is scarcely any DO^18 evaporated from polar waters, relatively speaking, and the ratio found in the cores is much higher than what can be physically evaporated from waters above 50N..a good 70-80% of the DO^18 precipitated over polar regions was not locally evaporated.

Similarly when an ice core shows a temperature change of 10C in a short period of time during the Younger Dryas it doesn't mean that the mean global temperature varied by 10C - obviously the oceans can't warm or cool that quickly.

Unfortunately, this is not the case either, because (as has been explained) the isotope ratios in the ice cores depict hemispheric SSTs, not global SSTs or regional SSTs. The Vostok cores, for example, can only depict southern hemispheric temperatures due to the nature of the Hadley Cells..visa versa for the GISP2 cores.

[ORH_wxman]

At least half of that warming occurred before CO2 levels had increased significantly. We were just rebounding from the Little Ice Age. It is very possible that CO2 only accounts for a small portion of that warming. Additionally, I am not so sure we even have warmed that much. How well did we measure global temperatures in the late 1800s vs Today?? apples to oranges. For the sake of argument if we warmed only .8C it is within the realm of natural variations in the Holocene and I doubt it would cause any major disruption of weather systems. I have been forecasting the weather for 25 years and things don't seem that different. what is different is how the media now reports on weather front and center 24/7. so the perception is that there is more severe storms....

 

With zero feedbacks, doubling of CO2 from preindustrial levels is an increase of 3.71 W/M² which corresponds to a warming of roughly 1.1C. It is very unlikely that there are zero feedbacks...and the feedbacks are likely to be positive, so we would expect more warming than 1.1C.

 

The temperature record is plenty good enough too that we can be confident that we have warmed 0.8C since the late 19th century. Any uncertainty is fairly minor on that front.

[AvantHiatus]

At least half of that warming occurred before CO2 levels had increased significantly. We were just rebounding from the Little Ice Age. It is very possible that CO2 only accounts for a small portion of that warming. Additionally, I am not so sure we even have warmed that much. How well did we measure global temperatures in the late 1800s vs Today?? apples to oranges. For the sake of argument if we warmed only .8C it is within the realm of natural variations in the Holocene and I doubt it would cause any major disruption of weather systems. I have been forecasting the weather for 25 years and things don't seem that different. what is different is how the media now reports on weather front and center 24/7. so the perception is that there is more severe storms....

True but several dozen notable events have occured in various parts of the world that have shattered all records from the 20th century. Starting with the 2005 Hurricane Season, extreme AMOC slowdown in 2009/2010, record snowiest snowfall in my local area (which is below 39N) in February 2010, Record heat/drought for the midwest during the string of La Ninas from 2011-2012. Record conus heat in Summer 2012 + super Derecho. Worst California drought 2013-ongoing (and warmest winters). Warmest Winter for Europe 2014/2015. Unprecedented spikes in early season hurricane activity in WPAC. Polar vortex invasions, etc, a generally chaotic blocking pattern worldwide even southern hemisphere. Not to mention all the crap Australia has been thru even record dust storms and heat.

 

I hope you find this insightful. Opps forgot Hurricane Sandy, lol.

[FloridaJohn]

At least half of that warming occurred before CO2 levels had increased significantly. We were just rebounding from the Little Ice Age. It is very possible that CO2 only accounts for a small portion of that warming. Additionally, I am not so sure we even have warmed that much. How well did we measure global temperatures in the late 1800s vs Today?? apples to oranges. For the sake of argument if we warmed only .8C it is within the realm of natural variations in the Holocene and I doubt it would cause any major disruption of weather systems. I have been forecasting the weather for 25 years and things don't seem that different. what is different is how the media now reports on weather front and center 24/7. so the perception is that there is more severe storms....

 

I notice that you have large doubts about the instrumental temperature record, however you seem quite confident in the measurements of the Holocene temperature record. I believe there is more uncertainty in that record than there is in the more recent instrumental temperature record. There does exist some Holocene temperature records that are cooler than our current temperatures. If I remember correctly, there is something like a 75% chance that we are already warmer than the highest temperature of the Holocene. Either way, it is safe to say that we are very near the top of the Holocene (either slightly above or slightly below).

 

Interestingly, over your career you should be seeing less extreme events. The fact that the relative frequency has stayed the same is actually evidence that they are increasing, since rare events should become rarer over time (i.e. more years to divide by the number of rare events). Here's a pretty good description of that phenomenon. These extreme events are not evenly distributed around the globe, though. So it is possible that in your particular location the weather has been pretty stable. That doesn't mean it has been like that everywhere. I do agree that the news stations are hyping it up more than they used to which also affects our perceptions on what is happening.

[Isotherm]

With zero feedbacks, doubling of CO2 from preindustrial levels is an increase of 3.71 W/M² which corresponds to a warming of roughly 1.1C. It is very unlikely that there are zero feedbacks...and the feedbacks are likely to be positive, so we would expect more warming than 1.1C.

 

The temperature record is plenty good enough too that we can be confident that we have warmed 0.8C since the late 19th century. Any uncertainty is fairly minor on that front.

 

 

The bolded portion is much more in dispute. There are countless peer-reviewed studies I've come across that assert the net feedback to be weakly positive, around zero, or some even on the negative side. In fact, I've seen quite a few studies with projected ECS levels under 1.1C due to the possibility of incorrectly assigning positive feedback where it could be negative, and thus arriving at ECS values lower than the zero-feedback response (doubling of Co2 1.1C). Given the fact that plentiful peer reviewed research exists on the lower-end of the ECS scale, I don't think we should make any assumptions at this point. I think the IPCC ECS range of 1.5-4.5C should be changed to 0.5-4.5C (and at least 1.0-4.5c) to more objectively account for the full-range of peer reviewed studies. One of my primary concerns has been the potential exaggeration/over-assignment of positive feedbacks by modelling, and assumption of no negative feedbacks when there may very well be some. I'm not asserting that we'll be looking at under 1.1c of warming, but I am saying that there are countless peer reviewed papers doubting the notion of significant or even moderately positive feedbacks beyond the 1.1C/per doubling warming.

[ORH_wxman]

The bolded portion is much more in dispute. There are countless peer-reviewed studies I've come across that assert the net feedback to be around zero or even on the negative side. In fact, I've seen quite a few studies with projected ECS levels under 1.1C due to the possibility of incorrectly assigning positive feedback where it could be negative, and thus arriving at ECS values lower than the zero-feedback response (doubling of Co2 1.1C). Given the fact that plentiful peer reviewed research exists on the lower-end of the ECS scale, I don't think we should make any assumptions at this point. I think the IPCC ECS range of 1.5-4.5C should be changed to 0.5-4.5C (and at least 1.0-4.5c) to more objectively account for the full-range of peer reviewed studies. One of my primary concerns has been the potential exaggeration/over-assignment of positive feedbacks by modelling, and assumption of no negative feedbacks when there may very well be some. I'm not asserting that we'll be looking at under 1.1c of warming, but I am saying that there are countless peer reviewed papers doubting the notion of significant or even moderately positive feedbacks beyond the 1.1C/per doubling warming.

 

 

I've only seen a handful of studies that show anything under 1.5C....they are certainly in the minority. I think you are overstating how many there are.

 

I've seen several studies that show TCR closer to 1.1C but not ECS.

[Isotherm]

I've only seen a handful of studies that show anything under 1.5C....they are certainly in the minority. I think you are overstating how many there are.

 

I've seen several studies that show TCR closer to 1.1C but not ECS.

 

 

Yes, there are numerous studies with low TCR's, but I also have (estimating) at least 25+ papers concluding ECS values of 1.5C or lower. Again, not saying that's necessarily what I believe, but there definitely seems to be enough disagreement for the door to be left open < 1.5C. There are an even greater amount of recent studies concluding 1.5C-2.0C ECS. Maybe I will create a new thread pertaining to this topic.

[nflwxman]

Yes, there are numerous studies with low TCR's, but I also have (estimating) at least 25+ papers concluding ECS values of 1.5C or lower. Again, not saying that's necessarily what I believe, but there definitely seems to be enough disagreement for the door to be left open < 1.5C. There are an even greater amount of recent studies concluding 1.5C-2.0C ECS. Maybe I will create a new thread pertaining to this topic.

 

Those studies seem to place a lot of emphasis on the empirical style and generally do not address the paleoclimatic evidence.  As we've seen, small timeframes of surface temperature can be subject to too many natural factors and/or coverage bias (ie. Arctic) to be used to create a stable ECS.  

 

We've risen 120 ppm of CO2 concentration and the temperature has risen about 0.9C.  Would another 180 ppm only lead to a temperature rise of 0.6C?  It just doesn't add up, especially when you consider ECS is lagging behind CO2 several decades (at least).

[ORH_wxman]

The energy budget empirical studies that go back to the mid-19th century are not affected by the hiatus as much. That is the advantage of them.

[nflwxman]

The energy budget empirical studies that go back to the mid-19th century are not affected by the hiatus as much. That is the advantage of them.

Agreed.  And for the most part they still fall in the 2.2-3C range for ECS.

 

The whole debate about ECS becomes a bit more muddied when one considers increasing feedbacks ala methane, albedo drops.  To date these feedbacks have been likely muted, but tipping points will make a generally linear temperature rise more exponential in the future.

[chubbs]

Agreed.  And for the most part they still fall in the 2.2-3C range for ECS.

 

The whole debate about ECS becomes a bit more muddied when one considers increasing feedbacks ala methane, albedo drops.  To date these feedbacks have been likely muted, but tipping points will make a generally linear temperature rise more exponential in the future.

GHG forcing has increased by 0.66% per year since 1979, this rate of increase produces a doubling in a little over 100 years.This makes it easy to do the math when relating temperature to forcing.  Surface temperature has increased by 0.0158 per year on GISS in the same period. Ignoring aerosals, other non-GHG forcings and natural variability, this gives a very rough TCR estimate of 1.6C, which is consistent with a mid-range ECS.

 

GHG forcing from here: http://www.esrl.noaa.gov/gmd/aggi/aggi.html

[Isotherm]

Those studies seem to place a lot of emphasis on the empirical style and generally do not address the paleoclimatic evidence.  As we've seen, small timeframes of surface temperature can be subject to too many natural factors and/or coverage bias (ie. Arctic) to be used to create a stable ECS.  

 

We've risen 120 ppm of CO2 concentration and the temperature has risen about 0.9C.  Would another 180 ppm only lead to a temperature rise of 0.6C?  It just doesn't add up, especially when you consider ECS is lagging behind CO2 several decades (at least).

 

 

The question becomes, however: is the paleoclimate data sufficiently reliable/accurate as it pertains to inferring climate sensitivity, especially given the numerous uncertainties regarding cloud feedback, dust loading, and other mechanisms? I think the observation based studies tend to be more representative of how the climate system is behaving/responding in the presence of various forcings. There are obviously limitations with both types of studies, but I think there's more with usage of paleoclimate data as it pertains to inferring climate sensitivity.

[AvantHiatus]

The question becomes, however: is the paleoclimate data sufficiently reliable/accurate as it pertains to inferring climate sensitivity, especially given the numerous uncertainties regarding cloud feedback, dust loading, and other mechanisms? I think the observation based studies tend to be more representative of how the climate system is behaving/responding in the presence of various forcings. There are obviously limitations with both types of studies, but I think there's more with usage of paleoclimate data as it pertains to inferring climate sensitivity.

Sounds like the old SOC all over again.

[ORH_wxman]

GHG forcing has increased by 0.66% per year since 1979, this rate of increase produces a doubling in a little over 100 years.This makes it easy to do the math when relating temperature to forcing.  Surface temperature has increased by 0.0158 per year on GISS in the same period. Ignoring aerosals, other non-GHG forcings and natural variability, this gives a very rough TCR estimate of 1.6C, which is consistent with a mid-range ECS.

 

GHG forcing from here: http://www.esrl.noaa.gov/gmd/aggi/aggi.html

 

 

It's a bit dangerous to estimate TCR that way unless you use an energy budget equation with it....because you are using relatively short time scales that can be affected by internal variability (an energy budget equation can offset some of that problem). The 1979-2015 period also includes two major volcanic eruptions in the first 12 years, so even an energy budget equation would be difficult since you'd have to account for those somehow.

[nflwxman]

GHG forcing has increased by 0.66% per year since 1979, this rate of increase produces a doubling in a little over 100 years.This makes it easy to do the math when relating temperature to forcing.  Surface temperature has increased by 0.0158 per year on GISS in the same period. Ignoring aerosals, other non-GHG forcings and natural variability, this gives a very rough TCR estimate of 1.6C, which is consistent with a mid-range ECS.

 

GHG forcing from here: http://www.esrl.noaa.gov/gmd/aggi/aggi.html

 

This also ignores any potential rapidly ampliying feedbacks such as albedo, methane, etc.  We can't assume that these feedbacks will be increasing linearly since the paleoclimatic evidence suggests otherwise.  I agree a hybrid approach should be taken when determining ECS, but I think several here have incorrectly dismissed ECS amounts of >3C due to static boundary condition empirical studies.

 

Who says the albedo drops on our ice sheets won't show a more dramatic drop between 400ppm-560ppm as compared to 280ppm-400ppm.  These empirical studies assume linearity, which is an inherent flaw.

[chubbs]

It's a bit dangerous to estimate TCR that way unless you use an energy budget equation with it....because you are using relatively short time scales that can be affected by internal variability (an energy budget equation can offset some of that problem). The 1979-2015 period also includes two major volcanic eruptions in the first 12 years, so even an energy budget equation would be difficult since you'd have to account for those somehow.

 Sure it could be off, but the longer we maintain a relatively steady warming the more likely the the middle estimates are correct.

[ORH_wxman]

Sure it could be off, but the longer we maintain a relatively steady warming the more likely the the middle estimates are correct.

Well you can easily move that number by 25% in either direction when you use the method you just did depending on your starting and end points.

[chubbs]

This also ignores any potential rapidly ampliying feedbacks such as albedo, methane, etc.  We can't assume that these feedbacks will be increasing linearly since the paleoclimatic evidence suggests otherwise.  I agree a hybrid approach should be taken when determining ECS, but I think several here have incorrectly dismissed ECS amounts of >3C due to static boundary condition empirical studies.

Yes.I do not advocate estimating ECS or even TCR this way. It is just useful in producing mileposts to check progress. If temperature trends diverge from recent history then there is evidence for a change in behavior.

[ORH_wxman]

This also ignores any potential rapidly ampliying feedbacks such as albedo, methane, etc. We can't assume that these feedbacks will be increasing linearly since the paleoclimatic evidence suggests otherwise. I agree a hybrid approach should be taken when determining ECS, but I think several here have incorrectly dismissed ECS amounts of >3C due to static boundary condition empirical studies.

Who says the albedo drops on our ice sheets won't show a more dramatic drop between 400ppm-560ppm as compared to 280ppm-400ppm. These empirical studies assume linearity, which is an inherent flaw.

Every single method has flaws. You pick your poison. The GCMs that claim we will warm 3-4c by 2100 have their own problems. You could easily argue that they are worse than empirical-based studies because they are already running unrealistically warm.

Expecting a big methane or albedo feedback is a major assumption. Both are not well supported in the literature. The hope for those models is water vapor feedback.

[chubbs]

Well you can easily move that number by 25% in either direction when you use the method you just did depending on your starting and end points.

 Sure I just used 1979 because the NASA GHG forcing series starts then on the website. However we've been locked into a relatively steady T increase since around 1970. The rate of temperature increase per unit of forcing was lower before 1970 and particularly before 1900. That is one reason the energy balance ECS estimates that go back that far are lower.

[nflwxman]

Every single method has flaws. You pick your poison. The GCMs that claim we will warm 3-4c by 2100 have their own problems. You could easily argue that they are worse than empirical-based studies because they are already running unrealistically warm.

Expecting a big methane or albedo feedback is a major assumption. Both are not well supported in the literature. The hope for those models is water vapor feedback.

 

Expecting a BIG abrupt feedback is not supported by literature, I agree.  Expecting an exponentially increasing feedback is, however.  Wildfires, Ice sheet darkening, permafrost melting, ect.  Whether there is a major tipping point before 560 ppm is unknown, but these empirical studies essentially ignore the exponential nature of these small, but sizable feedbacks.

 

GCMs probably won't be running significantly warm in 10 years, FWIW.  Just my personal prediction.

[ORH_wxman]

 Sure I just used 1979 because the NASA GHG forcing series starts then on the website. However we've been locked into a relatively steady T increase since around 1970. The rate of temperature increase per unit of forcing was lower before 1970 and particularly before 1900. That is one reason the energy balance ECS estimates that go back that far are lower.

 

You still need an energy balance equation regardless of the starting point or you end up making too many assumptions. Even using an energy balance equation starting in 1970s is dangerous...because you may be on opposite ends of natural variability...and you still have the volcano problem in the first half of the time period.

 

The energy budget TCR/ECS really isn't affected that much though by starting point...starting in the mid-20th century, you end up with an identical ECS as starting in the late 19th century.

 

 

Again, no method is perfect, but you try and minimize the number of assumptions that are made if you want to reduce the uncertainty.

[ORH_wxman]

Expecting a BIG abrupt feedback is not supported by literature, I agree.  Expecting an exponentially increasing feedback is, however.  Wildfires, Ice sheet darkening, permafrost melting, ect.  Whether there is a major tipping point before 560 ppm is unknown, but these empirical studies essentially ignore the exponential nature of these small, but sizable feedbacks.

 

GCMs probably won't be running significantly warm in 10 years, FWIW.  Just my personal prediction.

 

 

Perhaps not as a whole, but I'd be shocked if the higher sensitivity ones managed to have observations back within 5% confidence interval within 10 years. Remember that in the study that picked out a group of CMIP5 models that did OK during the hiatus, the average warming of those models was not among those on the higher end of sensitivity. They were fairly modest.

 

But that is all conjecture anyway at this point.

[StudentOfClimatology]

Sounds like the old SOC all over again.

What are you referring to, exactly?