With all of the emphasis that is often placed on hemispheric or global mean temperature trends during the past millennium, and the context they provide for interpreting modern warming trends, one thing is often lost in the discussion: space matters as much as time. Indeed, it is likely that the regional patterns of past climate changes, rather than simple hemispheric or global mean temperature trends, will best inform our understanding of the dynamical mechanisms involved. Since much of the uncertainty in future projections relates to regional climate change impacts, it makes particular sense to focus on those changes in the past that involve regional changes and the underlying mechanisms behind them.
For instance, melting of the cryosphere (and consequent rises in sea level), subtle shifts in drought and rainfall patterns, and extreme events, are all regional effects that could be important threats to ecosystems and our environment. Such changes are often associated with phenomena like ENSO or the North Atlantic Oscillation. Yet there remain large uncertainties about how such mechanisms will respond to anthropogenic climate change.
There are a number of potential ways forward to improve our understanding. A first step is to look directly at the time-series of specific systems (like the ENSO index or the ocean temperatures in the North Atlantic) and try to extend them as far back as possible using proxy data. This gives more information on what the natural variations in these phenomena look like, and thus a better idea of how big a forced response would need to be before it could be reliably detected. Secondly, we can look to see if there is a relationship between various natural drivers of climate change (volcanic eruptions, solar variability or orbital forcing say) and any characteristics of these phenomena – amplitude, frequency or duration. Do volcanic eruptions appear to affect El Niño for instance?
For phenomena that need annual or decadal resolution data to be resolved, the last millennium or so is an obvious (and only) time period to be looking at for it is only for that period that there is sufficient paleo-data coverage of high enough temporal resolution. Other periods – such as the mid-Holocene 6000 years ago – are also useful, but the results are more long-term in nature (there is also a discussion of the value of different periods for reducing future projection uncertainty in this recent paper).
There are a number of different approaches to looking at reconstructions in recent centuries – some rely on high density regional networks (as seen in this recent paper by Guiot et al concerning European temperature trends for which they mostly used pollen data) and some rely on wider networks of more diverse proxies which aim to capture longer-range correlations to specific phenomena (such as the recent Mann et al (2009) paper).
When this is done, people usually find that while it was relatively cool in global mean temperatures from the 1400s to the 1800s known as the “Little Ice Age” and relatively mild in the 900s to 1300s interval ( sometimes termed the “Medieval Warm Period”). But the spatial reconstructions reveal, however, why such global terms can be quite misleading, and why alternative phrases such as the “Medieval Climate Anomaly” are being increasingly favored by the community. This latter terminology recognizes that while the interval displayed significant climate anomalies, they varied greatly, even in sign, from region to region. Many of the more profound climate anomalies, moreover, involve variables other than temperature, such as drought, rainfall, and atmospheric circulation. Though the medieval period is seen to be modestly warmer globally in comparison with the later centuries of the Little Ice Age (the peak global mean warmth is likely comparable to mid, but not late, 20th century warmth), some key regions appear to have in fact been colder, while other regions appear to have been warmer. Southern Greenland, for example, appears within uncertainties to have been as warm as today. However, much of the tropical Pacific was unusually cold, suggestive of the La Niña phase of the ENSO phenomenon (a similar conclusion was reached by Trouet et al (2009)). Thus even though some locations may have been as warm or warmer than today, the hemispheric mean appears not to have been.
Why does this matter? It matters because there are plenty of factors that can affect the overall mean temperature (solar variability, volcanoes, greenhouse gases, internal variability etc.) and so it is hard, given the uncertainties in the solar or volcanic reconstructions to precisely attribute the paleo changes in the global or hemispheric mean to these factors. But if we can look at more complex fingerprints of the changes, it might be possible to be more quantitative in those attributions since the spatial fingerprints of the different factors are easier to distinguish. Furthermore, if we can clearly tie the regional patterns to the different forcings, we might be able to use that information to inform regional projections under future conditions.
Thus we can basically say that the warmer conditions of the Medieval era were tied to higher solar output and few volcanic eruptions and the cooler conditions of the Little Ice Age resulted from lower solar output and more frequent volcanic eruptions. But these drivers appear to have had an equally important, though more subtle, influence on regional temperature patterns through their impact on climate phenomena such as ENSO and the North Atlantic Oscillation. The modest increase in solar output during Medieval times appears to have favored the tendency for the positive phase of the NAO, associated with a more northerly jet stream over the North Atlantic. This brought relatively greater warmth in winter to the North Atlantic and Eurasia. A tendency toward the opposite negative NAO phase helps to explain the enhanced winter cooling over a large part of Eurasia during the later Little Ice Age period.
There is some model support for these patterns (see also instance Shindell et al, 2001) when the models include interactive ozone photochemistry to produce this dynamical response to solar forcing, but it is not captured in a simulation of the NCAR CSM coupled model which lacks those processes. Neither model simulation reproduces the apparent La Niña pattern seen in the Medieval temperature reconstructions:
Figure 1: Spatial pattern of mean temperature difference between the MCA and LIA periods (defined at the intervals AD 950-1250 CE and 1400-1700 CE respectively) compared with simulations of two different climate models forced with estimated differences in natural (volcanic and solar) radiative forcing between the two periods (Mann et al, 2009).
Other model simulations, however, using a climate model that exhibits a particular tropical Pacific mechanism, do reproduce such a response. In such models, the tropical Pacific counter-intuitively tends to the cold La Niña phase during periods of increased heating, such as provided by the increase in solar output and low volcanism of the Medieval era. If this response holds for the future, something that is still vigorously debated, it could imply a more La Niña-like response in the future. Most of the state-of-the-art climate models, e.g. those used in the IPCC Fourth Assessment, by contrast, suggest the opposite–a more El Niño-like future climate. The credibility of the models with regard to this phenomenon is not high, however, and lots more work is going to be needed (both on paleo-reconstructions and model improvements) before we can be confident in the future projections of changes in ENSO-like dynamics and mean state.
SA, thanks, that’s a good reference. Hadn’t seen it, though I have seen many of the same conclusions elsewhere.
It’s not what I was referring to in my comment re the Seager et al paper, which is what you quote. By “AGW profile specifically for drought in the US Southeast” I was trying to convey factors such as the “P & E” profiles, as well as larger issues such as the linkage (or lack thereof) to ENSO which the Seager paper addressed.
What Seager et al seems to say in this regard is that model work can reproduce Southwestern drought patterns much more robustly than Southeastern ones. The actual sentence from Seager et al. that led to my perhaps clumsy inference was this:
“As such model simulations forced by historical SSTs have very limited skill in reproducing the instrumental record of South precipitation variability and actual predictive skill will also presumably be low.”
(It’s from the abstract, and got ‘quoted around’ in previous posts.)
Since I’m quoting from the paper, the last sentence of the Conclusion is worth putting out there as well:
“. . .the projection of a modest reduction in the current century of P − E by the model ensemble indicates
that climate change should not be counted on to solve the Southeast’s water woes and is, in fact, as likely to make matters worse as better.” Which is essentially CFU’s point–warming will increase evaporation.
Thanks, Dappledwater (#245)–at least I know it’s not just me!
(Lovely screen-name, BTW, and very apposite for the subthread besides.)
re: #249
Yes, people may argue with what USGCRP writes, but it makes no sense for people to write vague generalities when there is current, high-quality, concise, well-written information easily available.
Recall the original post was about the need to better understand *regional* effects, as those strongly affect local/regional decisions and investments, especially for long-lived infrastructure.
Barton Paul Levenson, 229
“BPL: There is no “debate” on this particular issue except among the ignorant. That CO2 is rising and that it’s of human technological origin was pretty well established in the 1950s.”
I got the impression this blog is populated by sophists…
It is getting warmer. Fine
CO2 is rising. Fine
This CO2 is mainly from human activities. Fine
But to say that it is getting warmer because of human produced CO2, there is a huge missing step.
[edit — give us a break, the issue of attribution has been the focus of two decades of research, has been gone over many times on this site. The attribution of the warming of recent decades to human impacts can very likely be made, is the conclusion of the IPCC, all of the major national academies, etc. If you’ve got something new and interesting to say here, fine. But no trolling on old ground, ok?]
“That said, you seem to be talking past me.”
That’s because, Kevin, your post had a section dealing with whether you can or cannot ascribe a weather event’s genesis as a climate event. To answer that required I talk past you who were (rightly) saying this to those who are contending that was what I’d said.
It’s a little cumbersome because that content wasn’t directed at me, hence my wording was cumbersome.
“Msomewhat in support of your general points about how AGW may have affected the drought”
Aye, I have only maintained that it had an effect and that, absent any detailing to the contrary, that the event was made worse.
“I’ve responded at some length, CFU, but I truly am not trying to argue any position.”
And all I’ve tried, Kevin, is to argue my position wasn’t that the drought event was caused by AGW, merely made worse by it.
But it seemed to continually being missed or argued against.
I was arguing for point/counterpoint for the statements made, not ones that hadn’t.
“But what Seager et al. are saying is that, according to the best data that they have, the Southeastern drought did not differ from historical droughts. That’s not a theory, that’s what they found when they looked at the data.”
I would maintain that this is no proof that the changed climate didn’t make it worse.
Earth II may have had a less severe than normal drought that this earth, with the climate change, had a normally severe drought for the area.
This still constitutes AGW having made it worse (a light drought made a normal drought) and still doesn’t make the drought an exceptional event.
“It wasn’t drier, it wasn’t longer. And that’s what I find hard to argue with–unless one is prepared to do a thorough analysis of the same and/or related data.”
Whether the drought was drier or longer doesn’t change whether AGW had a worsening effect. It only means that this event wasn’t driven outside the normal range of events by it.
It’s the drought version of the 1999 “cooling”: it was climatically warmer, but the variations of other factors added to that warmer trend resulted in an event that was cooler.
Same here.
Sure glad the Arctic ice is recovering (according to the denialist side)
http://nsidc.org/data/seaice_index/images/daily_images/N_stddev_timeseries.png
—
A Climate Minute The Greenhouse Effect – History of Climate Science – Arctic Ice Melt
‘Fee & Dividend’ Our best chance for a better future – climatelobby.com
Learn the Issue & Sign the Petition
However, can I say it’s strange to talk about talking about the cause of something when nobody has talked about the cause of something?
Sure. Are you talking about this thread?
Strange.
CFU: I was making a general statement with support from the IPCC report and elsewhere in peer reviewed research in addition. I do not doubt there will be hot and dry regions affected gravely by warming. However, some crops adapt well to droughts and others to dryer conditions just fine. Some absorb more C02 and grow quite well too. Of course the increased growth from C02 can deplete the soil of nitrates and in some areas pests will become more plentiful and large in body mass. I am not accusing you of saying anything you have not, however, you focus so heavily on the aspects of droughts, it seems to me and few a others here, that you forget that AGW is not a complete detriment to crop yields and it is a tough thing to measure, or attribute GHG forcing to droughts becoming higher in magnitude or more frequent. That the mean global temperature is warming is indisputable and that GHG’s are VERY LIKELY (>95%) to be contributing to the warming of the globe is true based upon sound analysis. That some drought prone areas will become worse makes perfect sense and has data to support such assertions. I do think there are other areas to focus on which are easier to study and measure.
CFU you are a very sincere person, but you seem at times to get very easily offended and hyper. I was a bit like that when I first came to RC a few years ago myself. This is not about you though, this is about the issues we face in a warming world and GHG emissions roles in that.
http://www.scidev.net/en/news/rising-co2-levels-could-reduce-protein-in-crops.html (warming reduces crops’ nitrogen use, add more fertilizer)
http://oceanservice.noaa.gov/products/pubs_hypox.html (excess nitrogen runoff from overfertilization causing dead zones in fisheries)
” … she swallowed the spider to catch the fly ….”
Hank Roberts # 222: Thanks for the references and the discussion. I will add, though, that yes, they can lead to floods and erosion and the future may in fact hold such consequences for us, but nothing as of yet has occurred outside of historical happenings prior to the industrial revolution. We do have time to lower GHG’s, but I fear the next generation may have more consequences to face than people from our respective generations. That said, these predictions still need a lot of error analysis and more data collection to fine tune them. We should look at the current consequences we are seeing now (which are plentiful enough) in warming, dimming, and overall consequences of pollution in general and find reason there enough to make positive changes in energy production and lowering resulting emissions. We can never give up all fossil fuels, but we can certainly lower their use to what is most appropriate with some adoption of carbon capture, I think. Looking at the potential for a few floods and worse droughts, is not going to put the fire under law maker’s and corporate CEO’s butts as expected anyways. Human beings like to suffer dire consequences first before they take action. This is true in transportation, factory conditions and the materials used in home building and plastic making…
Again there is time and the attribution of any current severe sediment loss and flooding relating to AGW is not strong as of yet, but other factors are like: aquatic life dying and becoming extinct, less forests to absorb the high C02 levels etc…
Kevin, I agree that paragraph looks strange. Read with the preceding paragraph, I parsed it as follows:
1. Most of the models project that, in the Southeast, there will be a net drying (negative P – E) because, though precipitation will increase, evaporation will increase more. The projections are not very robust (a third of models say otherwise).
2. The models also project, more robustly, a net drying of the Southwest, but through a different mechanism: evaporation will actually decrease, precipitation will decrease more.
So the contrast, if I read it correctly, is between the different mechanisms leading to drying in the projections for the two regions in general. The contrast is not between the SW projections and the specific SE drought event. If so, moving that sentence up before the paragraph break would have made the meaning clearer.
3. Turning to the recent Southeast drought, observations seem to show that it was driven by decreased precipitation, not increased evaporation [which would contrast with the projected pattern for the Southeast, and I assume that’s the point they’re making].
I may well be wrong, but that reading seems to make sense of it.
Jacob, you’re right.
But I’m at a loss as to why you think you need to tell me this.
“however, you focus so heavily on the aspects of droughts,”
Yah. Did you read why? I put it out there several times. Here it is AGAIN.
https://www.realclimate.org/index.php/archives/2010/05/what-we-can-learn-from-studying-the-last-millennium-or-so/comment-page-3/#comment-174921
Now when you’re talking about droughts, talking about droughts is right, isn’t it?
“CFU you are a very sincere person, but you seem at times to get very easily offended and hyper.”
Well because I get people telling me that I’m wrong because you can’t say the drought was caused by AGW.
I never said that.
Isn’t it right to get pissed off when that happens?
And now I’m getting told off for concentrating on droughts in a question ABOUT DROUGHT.
If I were hyper I’d be a damn sight more vociferous, with damn good reason too.
“However, can I say it’s strange to talk about talking about the cause of something when nobody has talked about the cause of something?
Sure. Are you talking about this thread?”
Could you show me where someone has stated that AGW *caused* the SEUS drought?
If not, are you talking about THIS thread?
PS Jeffrey, to be clear: YES, I AM talking about this thread.
Which one are you reading?
http://www.ametsoc.org/policy/drought2.html“Drought differs from other natural hazards in several ways. First, it is a “creeping phenomenon,” making its onset and end difficult to determine. The effects of drought accumulate slowly over a considerable period of time and may linger for years after the termination of the event. Second, the absence of a precise and universally accepted definition of drought adds to the confusion about whether or not a drought exists and, if it does, its severity.”
“Drought is a normal, recurring feature of climate; it occurs in virtually all climatic regimes. It is a temporary aberration, in contrast to aridity, which is a permanent feature of regional climate. Drought should be considered relative to some long-term average condition of balance between precipitation and evapotranspiration (ET) in a particular area, a condition often perceived as “normal.” Common to all types of drought is the fact that they originate from a deficiency of precipitation that results in water shortage for some activity or for some group. It is also commonly recognized that other meteorological elements, such as temperature, wind, and relative humidity, may aggravate the severity and impacts of drought in some instances.”
http://www.ncdc.noaa.gov/oa/climate/research/prelim/drought/palmer.html
“While Palmer’s indices are water balance indices that consider water supply (precipitation), demand (evapotranspiration) and loss (runoff), the Standardized Precipitation Index (SPI) is a probability index that considers only precipitation. ”
If your definition of “drought” is based on the Palmer indices, since they estimate evapotranspiration which is temperature dependent, then a PDSI of -5 at an average temperature of 15 deg C is no more or less severe than a PDSI drought of -5 at 16 deg C, since the increase in evapotranspiration at the higher temperature will have been compensated by an increase in precipitation or decrease in runoff to arrive at the same PDSI value.
If you define “drought” by the SPI, then the impacts of equal index drought will be more severe at higher temperatures, since the increased evapotranspiration will increase plant moisture stress, reservoir drawdown, and “water shortage for some activity or for some group,” given the same amount of precipitation.
http://www.atmos.washington.edu/~dargan/summaries/flc07.html
“One of the most consistent responses of climate models to global warming is a widening of the Hadley circulation. Since the downward branch of the Hadley cell is associated with many of the largest deserts on Earth, the poleward expansion of the Hadley cell also means a poleward expansion of the dry zones. In climate models, the poleward expansion of the Hadley cell is closely linked with the predicted drought in the Southwest US, the Mediterranean, and other locations in similar latitude bands.”
But not the Southeastern US. Florida is a swamp, at the same latitude as the Chihuahua Desert in Mexico. North Carolina temperate forests get 1+ meter of rain per year; Northern Arizona at the same latitude gets ~ 1/3 meter per year. The presence of the warm Gulf and the Gulf Stream on 2 sides of the Southeast provides ready moisture when the winds are from the southwest around to easterly; southerly winds at the leading edge of low pressure areas which produce uplift and precipitation bring copious moisture into the southeast, but dry air from the mexican deserts into Arizona. The drying cause by expansion of the Hadley cell dry zone into Florida, Georgia, and the Gulf Coast will be ameliorated by proximity to the warm water source for moisture. As Seager et al point out “The Southeast clearly lies at the poleward fringe of the region of projected subtropical drying,” so short term variability(turbulence in the position of the edge) will often lead to favorable weather patterns bringing moisture ashore.
Seager et al say “In the post 2005 drought, according to the NCEP Reanalysis, E dropped along with P, indicating that the recent drought was driven by a reduction of P and not by an increase of E.” implicitly using Palmer definition of drought. Don’t tell the denialists, but if one accepts the AMS technical differentiation between drought and aridity, AGW will in many cases increase aridity, which indirectly increases drought.
Seager et al also find “… precipitation minus evaporation (P – E) decreases modestly in the annual mean, driven by increasingly negative P -E in summer.” Right now, the Jordan reservoir in central NC is 2 feet above control level, and consequently releasing ~30000 cubic feet per second of water into the Cape Fear River; that water will not be recoverable if it gets dry this summer. Summer decreases in water can’t be compensated by capture of winter precipitation in our current reservoirs to reflect a modest decrease in annual average – “that results in water shortage for some activity or for some group.” Development demand has been permitted in central NC based on reservoir delivery available with lower seasonal variation in precipitation than we will see with AGW. Raleigh has instituted year round water conservation rules: they will undoubtedly become more strict and more expensive as the effects of AGW unfold.
“but nothing as of yet has occurred outside of historical happenings prior to the industrial revolution.”
Here’s a thought experiment.
The effect of a process is randomly distributed in strength around a value 1.0. It is a poisson distribution, so goes all the way to infinity.
Chance of an event being less than 1.0 strength: 50%.
Now increase the severity of ALL events (add an active ingredient, warm it up, whatever) by 4%.
Chance that an event is less than 1.0 strength: very slightly less than 50%.
So you can’t say “no effect” just because you’re seeing one event less strong than the average.
A history spanning 200 years will show 2 one-in-a-hundred-years events in the past. If they are now once-a-decade, in the next 10 years you’ve seen a third event that is no stronger than ones you’ve seen before TWICE.
So you can’t say “no effect” just because you’re seeing an event that has been seen before.
Your position is wrong in so many ways, it’s not even good enough to be merely wrong.
226, CFU: You’ll never know not because you’re 63, but because you DO NOT WISH IT TO BE.
That is something that you can not possibly know.
What’s more curious about your inference is that proponents of the AGW theory have claimed that they wish it were not true, so that even known wishes have ambiguous evidentiary value.
RC, any plans on doing a post regarding Lyman et al and their newly published* integration/assemblage/synthesis of various ocean heat content studies?
In particular it would be interesting to hear any rumors concerning plans to follow ocean heat a bit deeper. I see that Gregory Johnson has published several papers on deeper heat content showing small but statistically significant warming so there’s at least some activity in that department.
Wouldn’t it be great if some ARGO-like buoys capable of deeper operation were launched? Even a few hundred might be a help w/regard to temperature and of course it would also be fascinating to track where they popped up.
* Robust warming of the global upper ocean
John M. Lyman, Simon A. Good, Viktor V. Gouretski, Masayoshi Ishii, Gregory C. Johnson, Matthew D. Palmer, Doug M. Smith, Josh K. Willis
Nature 465, 334-337
“That is something that you can not possibly know.”
“Ye shall know them by their fruits” (Matt 7:16 )
Arrgh – should have been “other meteorological elements, such as temperature, wind, and relative humidity,”
# 266 Now, we do not have any bridge in our communication.
CFU I did, however, enjoy your thoughtful post response on the quantum computer.
On statistics, droughts and floods:
Speaking as an old farm boy, and hence about things kids learn before they’re 10:
1) Average rainfall matters.
2) But variability often matters a *lot* more, in 2 ways:
the mean might stay constant, but increasing variability tends to cause:
a) Droughts get longer or worse, sometimes, and one long enough/bad enough is The End.
b) At the other extreme, extra precipitation is only useful to the extent that you don’t get flooded, and up to the point where the reservoir capacity is exhausted. AS I recall, one of the problems in the SouthEast is the lack of adequate reservoir capacity, hence states fighting over water rights, something long familiar to the US West.
# 273 John Mashey, well said again.
CMS, Brian, thanks for your thoughtful responses. CMS, your reading does make sense–though when I think of how dry the soil became during the drought, it’s hard for me to imagine how E possibly could have increased after the first year or so–there was so little moisture left there to evaporate. (Yeah, I know, if that were quantified I might see it differently.)
Brian, some good info to chew on.
John Mashey, well said indeed–though it feels a bit odd to me to describe Lake Lanier as “inadequate,” I suppose it is indeed a logical description relative to the need for water downstream.
Septic Matthew, allow me to translate CFU’s snark: I believe he means that you do not wish to know–and correspondingly that if you did wish to know, you could reach the same level of confidence (e.g. 90-95%) that countless scientists have reached before you.
“enjoy your thoughtful post response on the quantum computer.”
It’s not all that deep: I know how to set up two qbits but that’s as far as what I could follow took me.
Rather the same with normal computers, though: try reading how to write a ULA or a floating point converter using only NAND gates.
Makes your head hurt…
Mind you, I guess they use hardware descriptive languages to build them now, rather than go through the building blocks.
re 271: the point is that your position I quoted in 266 is a valueless statement. Either trivially true, in which case, adds nothing, or very wrong indeed in that you wish to draw a conclusion from it (because it IS valueless).
Yes, that event wasn’t outside the normal range.
But then a normal range includes one-in-ten-thousand-year events.
Heck, a once-in-a-decade event turns up and you have no proof of the *magnitude* of the effect until you’ve had several in a decade. However, each event is STILL only a one-in-a-decade event.
A hurricane that is force 3 is still fairly mild, but if it had been 2C cooler on the ocean, it would have been a force 2.
Did not the temperature of the ocean make it worse? Even though a force 3 hurricane is not unusual?
Yes. Yes it did.
I’ll have several comments on “The timing of Pleistocene glaciations from a simple multiple-state climate model” by Didier Paillard
http://www.nature.com/nature/journal/v391/n6665/full/391378a0.html
for which one mght want the pdf for the differential equation in question. After explaining what’s going on throughout the entire
http://en.wikipedia.org/wiki/Quaternary
I’ll attempt to relate this elegantly simple model to the climate of the last two millennia. But first we want to have some understanding of the last half of
http://www.globalwarmingart.com/wiki/File:Five_Myr_Climate_Change_Rev_png
and we’ll start with the last 1.1 million years with the climate cycling from
mode 0: interglacial
mode 1: interstadial (mild glacial)
mode 2: stadial (full glacial)
and back to mode 0. These three modes are supposed to be due to the three states of MOC, which is at least plausible.
The state variable is v = v(t) to represent something similar to ice volume, but as we can only view the d18O proxy (as linked above), v(t) actually means something more like 60% ice vloume, 40% deep ocean temperature (see Willy Broecker,’s “The Great Ocean Conveyor”). Anyway the differential equation in the absense of forcing is
dv/dt = z(m) – v
where z(m) is the stable value of v(t) depending upon mode m. If perturbed away from z(m), v(t) relaxes back to that value along a decaying exponential. Incidently, I’ve chosen a time unit so that the characteristic time of the relaxation is unity, tens of kiloyears for this model.
Now we add the radiative, orbital forcing F = F(t) in the far north:
dv/dt = z(m) – v – F
so that the equation is relaxing to the (always changing) (z(m)-F(t)). But more, once a threshold is reached the modes switches to the new mode
(m+1) mod 3.
[Each of the three modes have possibly different characteristic relaxation times, a detail I ignore for simplicity.]
Rather amazingly, at least to me, Didier Paillard is able to give a decent account of of the last 1.1 million years of a benthic d18O record. The results are insenstive to wide variations in mode switch values of v, characteristic times and somewhat insensitive to the choice of orbital forcing reconstruction [a difficult astronomical calculation]. I’ve studied two other, newer attempts to reproduce the “ice age” cycling. This one is the simplest and clearest, involving but one ODE with the only nonlinearity being the mode switching.
# 277: Yeah, I recently took a few computer information systems and basic programming courses. The quantum internet is around, but the computer is not quite there yet. I am by no means an expert in that area, but it is a fascinating area just the same.
# 278: No, not always, and not in the context of regional climate changes. Droughts worsened by warming probably will happen and in the near future we should be able to resolve some issues in way of attribuion and prediction, but we cannot do that yet AND warming actually helps some areas with crops AND some areas which cool due to local wind and temperature shifts also benefit. This is based upon peer review and recent reporting in several scientific magazines as well. C02 can temporarily aid plant growth and then inhibit nitrate uptake as the article Hank referenced also, but not all plants have the same issues with this. We do need to add more nitrates to soil that needs it and use more gentically modified crops that can adapt to changes that are detrimental to crop yields. That is also stated in the science and Bio-engineering. Even if GHG emission are reduced greatly we still have problems to face and so adapting is a very good idea.
When considering the issue of drought and extreme weather, it is important to realize that climate change can increase both drought AND flooding in the same location. If more precipitation falls in rare, severe events, it not only causes floods, but also erosion of topsoils. What it does not do is recharge aquifers.
I saw a lot of this sort of weather when I lived in Africa–flooding in the monsoon causing erosion and washing away crops if it came in the wrong season, followed by bone-dry, dustbowl conditions–and all in a region that gets over a meter and a half of precipitation in a year!
# 281 Excellent points. Well said. CFU pay attention to Ray’s post,as they get the point across in a real way:)We all learn from him.
re: #281
Yes, and closer to home, this is exactly the issue that California runs into sometimes. Much of the state water infrastructure was deigned to depend on a huge natural reservoir, the Sierra snowpack. Warming makes a higher % of precipitation fall as rain, and makes the snow melt faster in the Spring, so it is quite possible to get both flood and drought. Since much of CA does *not* get a meter and a half, this matters… especially since ~half the US fruit and veggies are grown here.
# 283: Yeah I have lived here in California for the past 3 plus years now. Yet we still have an enormous amount of fruits and vegetables along with a crack team at Berkeley studying ways to keep agriculture thriving as it is gradually receding in its yields here.
[Response: Er, no, that would be Davis, and some at Riverside.–Jim]
269, CFU: “Ye shall know them by their fruits” (Matt 7:16 )
Do you pay attention to what you write? You claimed to know my wishes.
276, Ray Ladbury: Septic Matthew, allow me to translate CFU’s snark: I believe he means that you do not wish to know–and correspondingly that if you did wish to know, you could reach the same level of confidence (e.g. 90-95%) that countless scientists have reached before you.
I think that translation is at variance with the actual language of his post. I agree that it may have been a snark instead of a thought.
Continuing comment #279: Didier Paillard then did the last 2 million years and it is clear he could have done the entire Quaternary. This required, it seems, rather more careful choices of mode switching values and characteristic time constants. In addition, the decline in average CO2 concentrations was mimicked by a linear increase in a mode switch constant; also a linear increase in solar insolation.
Comparison between the calcuated values for v and a benthic d18O record is done by eye in both the time and frequency domains. By eye the time domains are similarly featured but more impressive is the striking agreement between the two evolutive spectra (wavelet transforms). The switch from obliquity period dominated cycling to the long period cycling of the last 1.1 million years occurs right on schedule. The other features of the evolutive spectra are in close agreement as well.
Niether of the other two attempts I’ve read about even attempt this longer period analysis, so it is not clear that either would succeed. As it is, Didier Paillard’s model (so far) offers the more explanatory power.
David tell us more; 2,000,000 years is a long time.
Papers citing Paillard’s 2001 paper “Glacial cycles: Toward a new paradigm”
http://scholar.google.com/scholar?cites=8623472388026150541&hl=en&as_sdt=2000
Continuing comments #279 & #286: about 2000+ years ago, orbital forcing was close to the threshold for a switch from mode 0 (integlacial) to mode 1 (mild glacial) but of course that didn’t happen. Figure 3 in Archer & Ganopolski (2005) indicates that the threshold wasn’t reached in their analysis, irrespective of anthropogenic AGW. Crucifix * Rougier (2009) use a different climate model, nonlinear but without modes, and specifically test the hypothesis regarding a (mild) glacial at this time in the absense of AGW for the last 8000 years. That is, they stop parameter training at 8000 ybp and then extrapolate with those parameters; no glacial, even mild, until around 50–60 thousand years from now. That agrees with Archer & Ganopolski. But for a certain range of a threshold parameter value in Didier Paillard’s model, all mode transitions remain the same (for the past 900,000 years) except at the current time, when a mild glacial is underway in the model.
So it might well be the case that anthropogenic influences on climate, even those of 2000+ ybp, were just enough to avoid such a transition. The low orbital forcing certainly helps to explain why the past two millennia are the coldest of the Holocene in the GISP2 central Greenland ice core proxy.
Now one expects some phase lag between the forcing (orbital in this case) and the response (temperature). A lag of approximately 1610 years is plausible; the deep ocean responds only slowly. So in part, LIA might be attributed to an orbital forcing response.
Most nonsensical cause of global warming I have heard so far: “Nuclear testing in the 1950s tilted the Earth’s axis.”
We are up against some really strange ones. I hope I clarified the issue a little for him.
# 290 I know what you mean. Awhile back on Watts’s site some people had the audacity to state that since C02 is heavier than air it does not rise. Some really strange ones indeed.
# 289 some interesting stuff, David and thank you Hank for some papers using the reference.
222 Hank Roberts: Extreme hourly precipitation increase with increased temperature: Roger that. Maybe more. It rains a lot harder than it used to.
A very ironic point:
What I don’t like about hypotheses (by “like,” I mean, like as a fit) for the Medieval Warming Periods and the Little Ice Age being to any great extent carbon-related points to the truth about those of us who accept the scientific consensus on what’s been going on the past 125 years or so. They say we’re radicals, but we’re scientific conservatives. We like robust models and clear theoretical approaches that fit in with as much of the existing body of knowledge as possible. It doesn’t seem to me that we really have a big gap with the MWP or LIA to explain, over and above what we know from the geological record. The disputes have been over magnitude, I think.
I could add that we’re also on the conservative side of almost every battle here. Conserving species. Planning conservatively. Planning in a precautionary way. Assuming real income will be low, instead of high – that we’ll have to be frugal and efficient. Conserving our genetic heritage.
The denialists, on the other hand, often resemble the pronouncements of the early Soviets – no problems projected, just follow our economic and political advice and Nature and the real world will be conquered, and we can grow without limits.
I also agree with the comment early in this thread that if the MWPs and LIA were in fact substantially human and carbon-related, that is very bad news – good news, perhaps, for our credibility, although I wouldn’t bet on it, but terrible news for the future of humanity.
Jim and at Berkeley… you should not speak so soon.
James Hansen’s book: “Storms of My Grandchildren” must be read and OBEYED word for word by Congress. “Storms of My Grandchildren” has to become the law. Write and call and email as many senators as you can today and every day.
http://calclimate.berkeley.edu/publication/agriculture
Relevant publications and references on the website, however, here is one example from Berkeley regarding the economic impacts of climate change on agricultural water use in California:
http://calclimate.berkeley.edu/sites/default/files/13.%20Economic%20impacts%20of%20climate%20change%20on%20agricultural%20water%20use%20in%20CA.PDF
Of side interest reported on by Berkeley:
http://sciencereview.berkeley.edu/articles.php?issue=13&article=beespecies
In addition to the aforementioned research out of Berkeley and reporting on agricultural–climate change issues there are many other publications, reports and primary research on the relevan topics coming out of Berkeley.
[Response: Please, tell us more about the agricultural research coming out of the various units of the UC system…I mean, you’ve been in CA for 3 years now and all.–Jim]
http://www.cnr.berkeley.edu/csrd/global/flconf/ UC Davis is great too!
269, CFU: “Ye shall know them by their fruits” (Matt 7:16 )
I got to wondering: Was that an appeal to authority?
276, Ray Ladbury: “Septic Matthew, allow me to translate CFU’s snark: I believe he means that you do not wish to know–and correspondingly that if you did wish to know, you could reach the same level of confidence (e.g. 90-95%) that countless scientists have reached before you.”
If CFU’s comments require translation, shouldn’t you direct your remarks to him? (or her?)
“Do you pay attention to what you write? You claimed to know my wishes.”
Yes and what you say and what you state as truth show those wishes. The fruits of your labour are your posts here on RC.
All in denial of the problem.
cf “the warming has paused” earlier from you. Can only be a product of wishful thinking.
“When considering the issue of drought and extreme weather, it is important to realize that climate change can increase both drought AND flooding in the same location”
Yah, now when did anyone say rain?
There was already a drought.
If it’s raining, there’s not a lot of drought going on.