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One more data point

Filed under: — gavin @ 15 January 2020

The climate summaries for 2019 are all now out. None of this will be a surprise to anyone who’s been paying attention, but the results are stark.

  • 2019 was the second warmest year (in analyses from GISTEMP, NOAA NCEI, ERA5, JRA55, Berkeley Earth and Cowtan & Way, RSS TLT), it was third warmest in the standard HadCRUT4 product and in the UAH TLT. It was the warmest year in the AIRS Ts product.
  • For ocean heat content, it was the warmest year, though in terms of just the sea surface temperature (HadSST3), it was the third warmest.
  • The top 5 years in all surface temperature series, are the last five years. [Update: this isn’t true for the MSU TLT data which have 2010 (RSS) and 1998 (UAH) still in the mix].
  • The decade was the first with temperatures more than 1ºC above the late 19th C in almost all products.

This year there are two new additions to the discussion, notably the ERA5 Reanalyses product (1979-2019) which is independent of the surface weather stations, and the AIRS Ts product (2003-2019) which again, is totally independent of the surface data. Remarkably, they line up almost exactly. [Update: the ERA5 system assimilates the SYNOP reports from weather stations, which is not independent of the source data for the surface temperature products. However, the interpolation is based on the model physics and many other sources of observed data.]

The two MSU lowermost troposphere products are distinct from the surface record (showing notably more warming in the 1998, 2010 El Niño years – though it wasn’t as clear in 2016), but with similar trends. The biggest outlier is (as usual) the UAH record, indicating that the structural uncertainty in the MSU TLT trends remains significant.

One of the most interesting comparisons this year has been the coherence of the AIRS results which come from an IR sensor on board EOS Aqua and which has been producing surface temperature estimates from 2003 onwards. The rate and patterns of warming of this and GISTEMP for the overlap period are remarkably close, and where they differ, suggest potential issues in the weather station network.

The trends over that period in the global mean are very close (0.24ºC/dec vs. 0.25ºC/dec), with AIRS showing slightly more warming in the Arctic. Interestingly, AIRS 2019 slightly beats 2016 in their ranking.

I will be updating the model/observation comparisons over the next few days.

95 Responses to “One more data point”

  1. 51
    Carbomontanus says:

    Ladies and Gentlemen

    On alarmism:

    I wonder whether discussing and thinking in terms of catastrophies really is to our advantage. As Greta Thunberg has put it: “Nothing has been done and nothing taken serious from the side of “decision makers””

    On the contrary, when alarm goes, the luders will allways be there and see their chanse by rumors of sudden catastrophies, as if the paroles go for the world revolution, for which they are especially trained in order to enter the leading positions in society.

    . Proof, the Louisianna flood catastrophies. I saw it further directly during the H5N1 chicken flue karantene, where I was responsible for a henyard. Only 1 1/2 hours after Quarantaine- fall, the Mafia Boss of the street came on my door and ordered sheere violence to the quarantaine, pointing away from what we were told to obey to and take for serious.

    That quarantaine was having the same cause and root root as the CO2-AGW situation, namely too high wear on the biosphere. And was adminestered by the same UN in cooperation with science. The only difference was that the climate problem has a much longer inicial pace or rate.

    That quarantaine learnt me a lot, so I do not believe in alarmism and I do not alarm people. I leave that to the local luders and their organized crime..

    On the contrary, I do my very best to enlight people about Nature and Science and compulsary lectures from public school about scientific behaviours in everyday life, and how rather to become an amateur scientist in order to be responsible and critical and able to judge for yourself.

    I visit the semi-private meetings of the local national climate surrealists regularly, listen to their tellings, and tell them how to avoid the experts and instead understand how the basic observing and measuring devices for our orientation are working, and how they can be made and judged at home by any amateur technician and scientist.

    I showed them for instance an adiabatic lighter and a CD grid spectroscope with adjustable slit, that can disciminate incadescent light from discontinous spectra, thus better understand the molecdular absorption bands of the atmosphere. And next time I ought to show them an optical dubble beam detection experiment, and tell of Tyndalls very intelligent use of a termopile and a mirror galvanometer model 1859. Because they fight and scorn the methods and findings of William Herschel allready.

    Now they officially disqualify Tyndalls results telling that they are ruled out entirely by their own, more updated methods..

    But, in order to fight Tyndalls experiment and tell it to be false or misconsceived or irrelevant to global warming, you must further deny and commit class warfare against the permanence of energy and the permanence of heat plus Ørsteds electromagnetism and the Seeberg- effect.

    That kind of political class and religious warfare is real in our time, seeming alarming enough in itself.

  2. 52
    tamino says:

    Dan H. says, “Wildfires, like floods, are notoriously difficult to correlate with changing temperatures. Too many other factors (mostly human influences) after the outcomes.” Then he gives links to two scientific papers.

    Neither one is about wildfire. Neither one contains the words “wildfire” or “bushfire.” Neither one even has the word “fire” in it.

    This is the “Dan H.” method.

    The purpose of this blog is to make information freely available, not to give a forum for climate deniers to spew idiot nonsense. Not to borehole “Dan H.” is irresponsible.

  3. 53
    Thomas says:

    Jeez nigel at #49
    nigelj says: 26 Jan 2020 at 2:27 PM

    “Thomas @42”

    I am pretty sure comment numbers changed AFTER I posted my comment man!!!
    Because when I read replies yours’ came first (so I replied first) and then *** came after then i replied to their comments.

    my reply to #39 was referring to you (changed to #36?)
    my reply #36 was referring to #34 – jgnfld says: 23 Jan 2020 at 9:40 AM

    Can we smoke a peace pipe now?

    PS go read my comments again, even with the wrong numbers the TEXT (context) is still self-evident where i reply differently to each person .. isn’t it? Should be. (sigh)

  4. 54
    nigelj says:

    Thomas @53, yes lets smoke a peace pipe. I accept is was essentially a typo on your part, we all do that.

  5. 55
    nigelj says:

    Carbomontanus @51, alarmism does work if used properly. For example I read a published study on the use of fear as a motivator in health campaigns like anti smoking campaigns using empirical evidence from past campaigns. It found fear works, provided its based on solid facts backed up with good evidence. If fear is based on exaggerations, or is exposed to have a weak foundation, it can have the exact reverse effect. Can’t find the study now, but its almost intuitivly obvious anyway.

    I do sympathise with your personal circumstances of being intimidated by a denialist, and sometimes its wise to back down, but not as a general rule surely? We shouldn’t totally give in, and not express alarm or spread alarmist facts, because it could deny the public important information.

    You have a very good approach on explaining the science to denialists.

  6. 56

    Dan H., #44–

    To date, this has results in increased moisture in the more arid regions, with little change in the more humid areas. This is enhanced by temperature increases occurring disproportionately in the coldest times and regions. Models suggest that this will continue throughout most (if not all) of the 21st century.

    I really don’t see any support for these assertions in the linked papers. And more generally, what I’ve seen/heard is that most projections are, broadly speaking, for the ‘dry to get drier and the wet to get wetter.’

    One can form one’s own judgements based on AR5, Chapter 2. See Figure 2.29, p. 203.

    https://www.ipcc.ch/site/assets/uploads/2017/09/WG1AR5_Chapter02_FINAL.pdf

  7. 57
    William Jackson says:

    Does #51 make any sense to anyone? I have read it through several times and all I get is a headache.

  8. 58
    Dan H. says:

    Kevin @ 56,
    I will quote from the papers. From Garnaud and Sushama,

    “In response to rising atmospheric CO2 concentrations and the resulting increase in temperatures, the length of the growing season increases, as reported in other studies [e.g., Richardson et al., 2013].” and

    “CanESM2, show an overall increase in precipitation over North America [Arora and Boer, 2014], while DYN_RCP85 projects a decrease in annual precipitation (data not shown) over the coastal regions of North America and most of the southern regions.”

    From Murray-Tortarolo, et. al.,
    “This is, dry-season precipitation increased steadily, while wet-season precipitation remained constant, leading to reduced seasonality at a global scale. The decrease in seasonality was not due to a change in dry-season length, but in precipitation rate; thus, the dry season is on average becoming wetter without changes in length. Regionally, wet- and dry-season precipitations are of opposite sign, causing a decrease in the seasonal variation of the precipitation over 62% of the terrestrial ecosystems. Furthermore, we found a high correlation (r = 0.62) between the change in dry-season precipitation and the trend in modelled net primary productivity (NPP), which is explained based on different ecological mechanisms. This trend is not found with wet-season precipitation (r = 0.04), These results build on the argument that seasonal water availability has changed over the course of the last six decades and that the dry-season precipitation is a key driver of vegetation productivity at the global scale.”

    I prefer science over rhetoric any day.

  9. 59
    Leitwolf says:

    Seems like there is warming where there is air travel, and no warming where there is none. That is so surprising, since autonomous warming (that is: not explained by solar activity) occurs since the mid 70ies (which surprisingly does not fit the pattern of anthropogenic CO2), the time when air travel started to play a role, and since then strictly followed the ever increasing intensity of air travel. It is even more surprising, since there is not the slightest doubt contrails heat the planet.

    So I guess, logically, we should put all the blame on CO2 ;)))

  10. 60
    Mal Adapted says:

    Blog irritant Dan H. shakes some ‘data’ out of his coonskin hat, then executes his warrant:

    Wildfires, like floods, are notoriously difficult to correlate with changing temperatures. Too many other factors (mostly human influences) after the outcomes.

    He rebunks the “but uncertainty” lukewarmist meme in the model of Lomborg and RPJr, with a sciencey appeal to the non-expert. He even cites a couple of cherry-picked publications.

    I’m sure Dan H. worked hard on his comment. Yet clicking through his links, we find they don’t actually support his case. Regardless, scientific meta-literate non-experts can readily discern the emerging expert consensus for the link between AGW and recent catastrophic wildfires in N. America and Australia. Trained specialists, of course, recognize that wildfires have multiple causes from proximate to ultimate. Attribution to AGW is well-established by now, however. Try Causes and consequences of eastern Australia’s 2019–20 season of mega-fires, just published in Global Change Biology; also Australian blazes will ‘reframe our understanding of bushfire’ in Science a few months back, and Natural hazards in Australia: extreme bushfire in Climatic Change from 2016. For N. America, see for example Impact of anthropogenic climate change on wildfire across western US forests, appearing in PNAS in 2016, and the accompanying commentary, Human-caused climate change is now a key driver of forest fire activity in the western United States.

    And then there’s physics: ceteris paribus, warming means drying. That’s been consensus science since the mid-19th century (the Clausius-Clapeyron relation). Assuming no secular trend in other factors, higher annual average temperatures cause higher rates of evapotranspiration (combined evaporation from the soil surface and transpiration by growing plants), drawing down soil and fuel moisture earlier in the growing season. Warmer nighttime temperatures reach dewpoint less often, as well, so fewer fires die out on clear nights. It should be clear by inspection that holding all else constant, wildfires are more likely to ignite and spread than they would be with no warming trend. Well, here’s the 110-yr temperature trend for Australia.

    The link between AGW and regional drought is similarly apparent: warming is one key cause of drought, though not the sole cause. Hydraulic engineering and the global marketplace mitigate the impacts of drought on societies, obscuring the causal connection for modern laypersons. It’s clearer from a tree’s perspective: yes, droughts and fires have always happened; yes, AGW is making them worse. If I were an old ponderosa pine in northern New Mexico, I wouldn’t call uncertainty my friend. Having survived for centuries by sheer luck, I’d be alarmed!

  11. 61
    Al Bundy says:

    BPL’s page: Notice what’s happening in the table? The standard deviation steadily increases with sample size… until it reaches a certain point, after which the value is stable. Statisticians tell us the stable part is where you have an adequate sample size.

    AB: Adequate for what? I don’t see how that is adequate for finding tipping points, which is what we’re talking about.

    I would not call a clerical person a pencil pusher. More an accountant. Your definition is probably more widely held. And I tried to take the negativity from “pencil pusher”, to elevate you above accountant by complimenting your work.

    I apologize for any unintended offense and I say it again: I respect you and hold you and your work in high regard. You do what I don’t do, and you do it well. Ain’t diversity grand?

  12. 62
    Dan H. says:

    Mal @ 60,
    I will gloss over your sleazy attacks and get right to the message, since you appear to misunderstand Clausius-Clapeyron. Yes, droughts enhance the occurrence of wildfires. However, AGW has decreased droughts, as the physics dictates. Warming does not case drought, rather warmer temperatures have resulted in higher precipitation, and as the papers show, the arid regions have received more rainfall. This is evident in enhanced vegetation, as supposed by the papers linked, if you even bothered to read them.

  13. 63
    MA Rodger says:

    Leitwolf @59,
    The difficulty with any hypothesis linking the totality of AGW to air travel would be with the ‘strictly following’ assertion.

    While you say “autonomous warming (that is: not explained by solar activity) occurs since the mid 70ies,” the nature of that ‘warming’ is (1975-to-date) a strikingly linear rise in global temperature.
    Yet while it could be said that the mid-1970s was “the time when air travel started to play a role,” in that air travel was from that time no longer the preserve of the rich and privilaged, it requires far more to demonstrate that global temperature has “since then strictly followed the ever increasing intensity of air travel.”

    The difficulty is that, while the linear global temperature rise can be seen to begin in the 1970s (being absent in the 1960s), the rise in air travel has been exponential in form, rising from 310 million passengers annually in 1970 to 4,233 million in 2018. A hypothesis linking AGW thus needs to explain why the exponential increase in air travel from the (relatively) tiny 310 million figure of 1970 kicks-off AGW when that 310 million figure is itself the result of exponential growth running back at least to 1950 (see the 3rd slide in this ICAO presentation) and probably before that again – all this exponential growth in air travel during the 1950s & 1960s but not a whiff of AGW.

  14. 64

    A-B 61: I don’t see how that is adequate for finding tipping points

    BPL: You don’t use the standard deviation for finding tipping points. You would use something like a Chow test. It has nothing to do with adequate sample size.

  15. 65

    Dan H., #58–

    I prefer science over rhetoric any day.

    Well, that’s very nice. But now can you please explain to me how your cites support your assertion?

    Quote 1 says that growing seasons lengthen, which is uncontested, but irrelevant to the assertions you made.

    Quote 2 says that 1) per one model, generally North America will see increasing precipitation, which says nothing about arid vs. moist areas (the topic of your prior comment) and 2) decreases are expected (per another model) in “coastal” and most Southern areas of North America. OK, much of “coastal” North America is probably moist, but the southern tier pretty much spans the moisture gamut (compare Arizona to Florida in this respect!)

    Quote 3 talks about the seasonality of rainfall, which (IIRC) doesn’t really map onto “the coldest times” in any simple way. It says nothing about moist vs. arid places at all.

    So I’m afraid that even with the help of those specific quotations, I don’t “get it.” The quotes and the proposition they were to support still seem rather orthogonal to me–i.e., [metaphorically] “lying at right angles.”

  16. 66

    Leitwolf, #59–

    Seems like there is warming where there is air travel, and no warming where there is none.

    Really? Let’s have a look, shall we?

    Air travel:

    https://openflights.org/demo/openflights-routedb-2048.png

    Warming, per Gistemp 1981-present:

    https://data.giss.nasa.gov/gistemp/maps/index_v4.html

    I guess not.

  17. 67
    nigelj says:

    DDS says “However, AGW has decreased droughts, as the physics dictates.”

    Wrong. You provide no peer reviewed evidence that droughts have decreased globally. The IPCC report does not say droughts have decreased globally. The climate scientist in this article says droughts have already either increased or become worse:

    https://www.carbonbrief.org/guest-post-climate-change-is-already-making-droughts-worse

    The physics doesn’t dictate droughts would decrease. For example higher atmospheric moisture could just as easily lead to more intense flood events, and more droughts.

  18. 68

    DH 62: Warming does not case drought, rather warmer temperatures have resulted in higher precipitation

    BPL: The world is three-dimensional. Global warming moves the rain from continental interiors to coastlines, resulting in growing drought in continental interiors. Here’s some more information.

    http://www.ajournal.co.uk/pdfs/BSvolume13(1)/BSVol.13%20(1)%20Article%202.pdf

  19. 69
    Dan H. says:

    Kevin @65,

    Yes, the first citation mentions a longer growing season. It also states that through modeling, precipitation is expected in increase, except over the more humid coastal regions. Vegetation is expected to increase its water efficiency, resulting in enhanced growth. You could argue that the study is limited to North America only. However, this contradicts the claims of a drying biosphere.

    “It is interesting to note that the projected changes in annual precipitation by the end of the 21st century in the driving GCM, CanESM2, show an overall increase in precipitation over North America”

    “This suggests that the water‐use efficiency [Drake et al., 1997] of vegetation increases due to rising CO2 concentrations in the atmosphere. Indeed, with increased CO2 concentrations, vegetation can reduce the time during which the stomata are open, thus maintaining productivity while minimizing water loss.”

    The second citation using global precipitation data from 1950-2009. Their results were that arid region and dry season precipitation has increased, which resulted in enhanced vegetative growth.

    “This is, dry-season precipitation increased steadily, while wet-season precipitation remained constant, leading to reduced seasonality at a global scale. The decrease in seasonality was not due to a change in dry-season length, but in precipitation rate; thus, the dry season is on average becoming wetter without changes in length.”

    “We found small, mostly shortening changes in the dry-season length across a few key arid regions (e.g. South American and North American Plains), but strong regional changes in the dry-season precipitation rates.”

    “Overall, these results do not support the “dry gets dry” and “wet gets wet” hypothesis based solely on precipitation”

    “Therefore, across semi-arid and arid ecosystems, an increase in the dry-season precipitation represents a boost for dominant plant species productivity.”

  20. 70
    Mal Adapted says:

    Leitwolf:

    there is not the slightest doubt contrails heat the planet.

    Well, that’s interesting. I was ready to dismiss this claim as “chemtrail” conspiracism, until I did a little research, and learned that IR reflectance from contrails are believed to contribute more to the climate impacts of air travel than aircraft CO2 emissions do. See, for example, Aviation’s dirty secret: Airplane contrails are a surprisingly potent cause of global warming in Science last year. It cites this 2011 report:

    Air traffic contributed approximately 5 % to the anthropogenic climate forcing in 2005 (Lee et al., 2009), and its contribution is rising due to the large yearly increases in air traffic (ICAO, 2007). Radiative forcing due to contrail cirrus, consisting of linear contrails and the cirrus clouds arising from them, is the largest known radiative forcing component associated with air traffic, and is larger than the contribution of CO2 accumulated from aviation (Burkhardt and Kärcher, 2011).

    Not that I have any trouble believing it. We all know that while anthropogenic CO2 is the most important climate forcing, it’s not the only one operating. I hadn’t previously been aware of the contrail contribution, however. Thank you, Leitwolf.

  21. 71

    #69, Dan H.–

    Yes, the first citation mentions a longer growing season. It also states that through modeling, precipitation is expected in increase, except over the more humid coastal regions.

    I’ve just gone more carefully through that paper, and no, it doesn’t say that. What it says is this:

    Precipitation decreases with time over most regions in DYN_RCP85, and soil moisture and LHF tend to decrease with time over southerly regions.

    This is also shown graphically in their Figure 8 (which, by the way, shows a broadly similar result for the STAT_RCP85 simulation.) The point about plants using water more efficiently is correct, but not very relevant for us–though highly relevant for the cited paper, which is focused more on vegetation, not primarily the meteorology.

    And yes, this is for North America only, which limits its usefulness for characterizing global trends. It’s also based on one model only:

    The projected changes to biosphere and biosphere‐atmosphere interactions presented in this paper are based on a single RCM driven by a single GCM. To better quantify uncertainties, it is important to extend this study to a multimodel ensemble.

    Given that the second cite is observational and gives no future projections whatever, I think to speak airily of “models show,” as you did back in #44, is quite misleading. A reasonable reader would think that multiple models, and perhaps multiple studies at the global level, underpinned your claim. But it turns out that it rests on a single model result for a small fraction of the planet’s surface, which moreover you mis-stated by reversing the claimed sign of the dominant precipitation trend!

    Responding briefly to the quotes from the second paper, I still find the information about dry-season trends interesting in its own right, but not particularly relevant to the main question, which I take to be that there has been “increased moisture in the more arid regions, with little change in the more humid areas.”

    The point about the study results not supporting the ‘wet get wetter’ hypothesis is correctly stated, and I’m interested to see that result. However, it’s probably wise to highlight the caveat included: “based solely on precipitation.” Soil moisture, as we’ve discussed, is not solely ‘based’ on precipitation, and the whole point of the first paper cited was that vegetation itself modifies local meteorology. So we can’t just assume that in the real world the ‘wet get wetter’ hypothesis is now dead.

    The final quote provided needs some context. It said that:

    Therefore, across semi-arid and arid ecosystems, an increase in the dry-season precipitation represents a boost for dominant plant species productivity.

    Naively, this would seem to be a ‘good thing.’ However, if you read the whole passage and not just that one sentence, you get quite a different picture. There are ‘positive effects’ for vegetation, but:

    On the other hand, a more intense dry season in arid grasslands dominated by annual species, does not only lead to a decrease in vegetation productivity, but also to a reordering of species abundance…

    “Reordering of species abundance” could mean “loss of biodiversity” at worst, and at best it represents a distortion of, or at least change to, the ecologies of those areas.

    I’d like to end with another quote from the paper and a couple of observations. The quote:

    Our results are consistent with recent findings showing a probable increase in the number of extreme daily precipitation events across dry regions, which could explain the increase in dry-season precipitation rates. Additionally, Sun et al. found a decrease in global precipitation variability, with both the dry regions and dry seasons becoming wetter from 1940 to 2009. Thus, it seems that the length of the dry season has not changed globally during the last six decades, but the greater incidence of extreme weather events during the dry season has increased the daily precipitation rate, and thus, the dry seasons have become wetter on average.

    However, it is important to note that changes in forcing-mix could push the Earth-system in a different direction and thus, these hydrological trends may not be representative of what could occur in the future, particularly across extreme climate change scenarios. For example, aerosol-forcing was a key driver of global atmospheric trends during 1950–2009, but the signal is unlikely to remain into the future as positive greenhouse gas forcing dominates over negative aerosol forcing.

    So, if the dry-season trend is mainly due to an increase in extreme precipitation events, how good is that from a human perspective? The data in the paper seem to show that the ecosystem (writ large) benefits, at least as far as can be assessed by the bulk metric of NPP. But there is abundant anecdotal evidence that the same may not be true of agriculture. It may also not be true of human infrastructure: the heavy rains seen across parts of southeastern Australia recently have provided a welcome break in the horrendous fire season, but certainly have brought their own suite of problems:

    https://www.msn.com/en-au/news/australia/droughts-and-flooding-rains-australian-state-capital-records-its-highest-temperature-ever-as-severe-flash-flooding-turns-a-town-into-a-giant-swimming-pool/ar-BBZvlVZ?li=AAgfLCP

    But I digress…

    The second point made in the quote was that it is possible and perhaps probable that the observed precipitation trends they identify should be attributed not to warming per se, but to aerosol loadings in the atmosphere, and that the former is likely to dominate in future. That would not, of course, be consistent with your summary statement from #44 that “[moistening] will continue throughout most (if not all) of the 21st century.”

    My final observation is based not on the quote, but on Figure 3, which I link here for convenience:

    https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0190304#sec010

    For the study period, which ended in 2009, the wet-season trends look to be a pretty robust, even massive, declines for many well-populated areas, especially but not exclusively in the tropics and subtropics, including big swathes in Meso-America, northern India, Indochina, and east Asia, not to mention almost all of sub-Saharan Africa. It’s my understanding that for at least some of these areas rainfed agriculture is highly dependent upon the seasonal rains (eg., the “Dry Triangle” in Central America, Syria (!), or many parts of India). So what happens if the wet season trend does continue, whether due to warming or aerosols? Is that what we are now seeing WRT the Dry Triangle, where the wet season hadn’t, last I heard, actually arrived at all for several years?

    Desert plants in general have evolved to respond with ferocious speed to any rainfall they get, which may help account for the NPP trends found in the paper. Crop species, not so much.

  22. 72
    Mal Adapted says:

    Dan H., quoting his 2nd citation:

    “Overall, these results do not support the “dry gets dry” and “wet gets wet” hypothesis based solely on precipitation”

    I think I see his specific problem WRT this topic, confounding his cognitive biases: he is basing his definition of “drought” solely on precipitation. In scrupulous fairness, that’s the OED’s primary definition. I’m using a forest ecologist’s definition of drought as increased vapor-pressure deficit. My claim was:

    Assuming no secular trend in other factors, higher annual average temperatures cause higher rates of evapotranspiration (combined evaporation from the soil surface and transpiration by growing plants), drawing down soil and fuel moisture earlier in the growing season. Warmer nighttime temperatures reach dewpoint less often, as well, so fewer fires die out on clear nights. It should be clear by inspection that holding all else constant, wildfires are more likely to ignite and spread than they would be with no warming trend.

    Of course, there are always changes in other factors, on various timescales. Dan H.’s cited articles specify their geographic and temporal scopes: “continental” and “through 2100”, respectively. Yet isn’t it obvious that from a tree’s perspective, “drought” involves more than simply reduced precipitation? It’s true that CO2 fertilization enhances plant water use efficiency. One long-term effect of that on wildfire, is greater fuel accumulation during relatively drier years. Yet the long-term trend of slowly increasing global primary productivity is less relevant to the ecological impacts of short-term (seasonal, inter-annual) moisture deficits in historically drought-prone regions like northern New Mexico. Full disclosure: I recently moved from there, after a 10 year residence. Now I live in a different drought- and fire-prone area 8^(. I was perforce aware of wildfire during my time in N. NM. I may also comment later, on an impressive set of studies linking the regional mass piñon die-off of the mid-aughts to higher annual and especially winter temperatures, during a period of reduced precipitation that was no worse than a previous one in the 1950s, when a less severe (i.e. smaller area and lower elevation) piñon die-off occurred.

    Moving on: I linked above to Temperature as a potent driver of regional forest drought stress and tree mortality. The authors, some of whom I’ve met, studied the southwestern US from 1000 CE to 2007. From the abstract:

    If the vapour-pressure deficit continues increasing as projected by climate models, the mean forest drought-stress by the 2050s will exceed that of the most severe droughts in the past 1,000 years. Collectively, the results foreshadow twenty-first-century changes in forest structures and compositions, with transition of forests in the southwestern United States, and perhaps water-limited forests globally, towards distributions unfamiliar to modern civilization.

    Drought conditions outside the modern range were familiar, however, to the ancient cultures of the American Southwest. In Chaco Canyon, I was reminded of Shelley’s Ozymandias:

    Look on my Works, ye Mighty, and despair!

    But ignore that for now ;^). Dan H.’s ignorance of the ecological dimensions of drought exposes his scientific meta-illiteracy. I, OTOH, maintain that whether or not precipitation has changed in SE Australia and the SW USA in recent decades, warming in that interval is causing higher seasonal VPDs, i.e. drying, exacerbating the ecological impacts of “noisy” inter-annual precipitation fluctuations, and driving earlier/larger/longer/hotter wildfires. While Dan H.’s citations weakly support his point, his point is at best tangential (i.e. a “red herring”) to the relation between CO2-forced global warming, and regional droughts and wildfires. IOW, this guy can occasionally be clever, but he’s still a motivated lukewarmer.

  23. 73

    And speaking of drying in Central America, as I was earlier, what of the news in that regard? Still dry?

    Yep:

    https://globalimpactnews.com/2020/01/22/guatemalas-children-bear-brunt-of-prolonged-drought-and-rising-heat/

    Guatemala, which has one of the world’s high rates of child malnutrition, recorded more than 15,300 cases of acute malnutrition in children under 5 last year, up nearly 24% from 2018, according to government figures.

    The number of children acutely malnourished was the highest since 2015, when a severe drought hit Central America.

    Guatemala’s farmers are reeling from a series of prolonged droughts in recent years and from a lengthy heat wave last year as climate change brings drier conditions and erratic rainfall, U.N. officials said.

    Children living in poor highland farming communities and along the “Dry Corridor” – running through Guatemala, El Salvador, Honduras and Nicaragua – are bearing the brunt, they said.

    “There is an increase in cases of acute malnutrition that are related to climate change and the long periods of drought from June to October (last year),” said Maria Claudia Santizo, a nutrition specialist at the U.N. children’s agency UNICEF.

    Drought is also adding to the area of Guatemala suffering problems, she said.

    “With climate change, the dry corridor has expanded,” Santizo told the Thomson Reuters Foundation.

  24. 74
    Dan H. says:

    Mal,
    That is an extremely arrogant response. Assuming only your definitions and analysis are correct, while others are not. You complain that drought should not be based on precipitation only, yet you want to define drought based solely on temperature. Then you have the gall to call others ignorant. Perhaps a little self-reflection is in order. Get off your high horse and expand your horizons.

  25. 75
    Fred says:

    Mal #72

    Mal writes:
    “I, OTOH, maintain that whether or not precipitation has changed in SE Australia and the SW USA in recent decades, warming in that interval is causing higher seasonal VPDs, i.e. drying, exacerbating the ecological impacts of “noisy” inter-annual precipitation fluctuations, and driving earlier/larger/longer/hotter wildfires.”

    So where is the evidence of a drying trend in Australia? Pan evaporation data from Australia as a whole, as well as NSW and SE Australia shows a downward trend — that is, LESS drying: http://www.bom.gov.au/climate/change/#tabs=Tracker&tracker=timeseries&tQ=graph%3Devap%26area%3Dseaus%26season%3D0112%26ave_yr%3D0
    The downward trend is most evident in summer – the primary fire season.
    And this downward pan evaporation trend has been observed worldwide (according to “Global Dimming” BBC documentary). So perhaps global warming is driving increased cloud cover, thereby blocking infrared radiation from the sun. Or perhaps it’s aerosols from fossil fuel burning. Either way, it seems plausible that ACC is NOT driving climatic conditions supportive of fire, but instead is attenuating them, on balance.

  26. 76
    zebra says:

    Mal Adapted and Kevin McKinney, re Dan H #74,

    He actually says:

    “That is an extremely arrogant response. Assuming only your definitions and analysis are correct, while others are not.”

    Sorry guys, but you must take a lot of responsibility for this madness.

    Warrants, people, Warrants! Dan H (and Fred, just below, I think) confuse the practice of science with the naive interpretation of PoMo we see among the ill-literati: Anything goes! My definition is just as good as what those science guys say!

    It would be amusing if it weren’t so dangerous, and so very, very, sad, for those revered practitioners who created physics when there was no electric light and no flush toilets and life expectancy was the ultimate crapshoot. Is this what they invested their transient existence in… “all recited lists are equivalent, and there is no truth”?

    You guys have to do better. Stop playing this game.

  27. 77
    Al Bundy says:

    Fred: So where is the evidence of a drying trend in Australia?

    AB: Misquoting that short dude from what may be your hometown, Fantasy Island, “Da flames! Da flames!”

    Fire behavior is a grand measure of fuel moisture. Fuel moisture is a grand measure of effective dryness. That you can find an ineffective alternative measure means what?

  28. 78
    Al Bundy says:

    BPL: You don’t use the standard deviation for finding tipping points. You would use something like a Chow test. It has nothing to do with adequate sample size.

    AB: Good. I’m glad we agree.

  29. 79

    zebra, #76–

    My belief is that you are trying to help, zebra. (Although I’m not certain what that means to you, exactly; you see “madness” where I see a critical examination of certain assertions–a classical procedure to reach a more firmly-founded conclusion. So apparently we are not looking at the exchanges above from the same viewpoint at all.)

    So, can you be more explicit? What do you suggest I do differently–and to what end, exactly? What is the “madness” you see, and how exactly do you think I’ve contributed?

    Let me go first: My perspective is that I was examining, and in some cases challenging, particular statements made. Partially, that is for my own education–interaction is highly informative (e.g., that’s the model of the classic ‘graduate seminar’.) And partially, it’s because I think it’s worthwhile critiquing statements that may tend to influence opinion on policy, if those statements are not well-founded. (E.g., I think it’s dangerous to allow any form of “swift-boating.”)

    My expectation is not to ‘convince’ my interlocutors; as I’ve said before (though maybe not lately), that is in general a very unusual occurrence in these climate-related conversations. (Sadly.) My expectation is that observers will be more likely to conduct rational evaluations of the quality of the case that’s made, and act accordingly.

  30. 80

    Fred, #95–

    Fred, thanks for the link to the BOM data. It’s great to have some reasonably hard data to reference.

    However, when I looked at the graphs you linked to, I found myself rather in the position that poor old Victor repeatedly claims for himself: that is, I was far from certain that the trend you described as “evident” was really there. (I tried varying the parameters for the graph, too, finding that, for instance, while the data for South Australia look a bit more like there could be a declining trend, those for the country as a whole look more like a no-trend, to my eye at least.)

    Unlike Victor, I was not sure the claimed declining trend wasn’t there, either; what I saw was enormous year-to-year variability. While I’m no a statistic whiz–far from it!–I do at least know that that means that you are going to need a really strong trend to ‘punch through’ the noise. And most likely, you also need a robust statistical examination to discern said trend–eyeballing things just wasn’t going to cut it.

    And of course, you also claimed that there was a global trend toward less pan evaporation, though the only reference given was a “mention” in the documentary “Global Dimming.” The Australian data obviously had little to say about that.

    So I went looking at literature. This is the fun–or rewarding, anyway–part of participating, because it’s where you find the unexpected. There’s the delight of learning something, and maybe something really surprising to boot.

    First result:

    https://www.sfwmd.gov/sites/default/files/documents/tech_paper_sfer_107_r.pdf

    It’s a base an empirical study of pan evaporation in South Florida, but there’s also a pretty good literature survey to start off. And it turns out that your claim is (or was) well-founded:

    Literature reports of declining trends in pan and lake evaporation warrants studying the case for every region and its implications for water management. If true, the constant rates of decline reported in some literature are alarming, especially when projected with time and the possible changes in the environmental energy balance.

    (Opening of abstract.)

    They go on in the literature survey to identify and discuss papers which found this decreasing trend, which was enough of a ‘thing’ to merit a term: the “pan evaporation paradox”. However, they also note that this trend was by no means homogenous:

    A follow-up study of trends in pan evaporation and actual evapotranspiration across the conterminous United States showed that pan evaporation had an increasing trend in South Florida (Hobbins and Ramirez, 2004). A study on pan evaporation trends in the United States reported that pan evaporation had a decreasing trend in most regions except the southeast where the trend was increasing for the period 1948 to 1998.

    Moreover, the other side of the “paradox” is that while pan evaporation trends were more likely to be negative, trends for evapotranspiration in the environment were more likely to be positive. For instance:

    Szilagyi et al. (2001) acknowledged the conclusion that pan evaporation has been documented as decreasing in the last 50 years. An attributed cause was the increase in cloud cover associated with climate change. The study concludes that at the same time, over the conterminous United States, actual annual evapotranspiration has increased at a rate of 3 percent.

    To cut to the chase, the paper concluded that:

    The conclusion is that pan evaporation measurements are prone to too many sources of errors to be used for trend analysis. This condition is demonstrated in South Florida and in other regions by differences in magnitude and direction between spatially related pan stations and unexplainable observations.

    That paper was from 2010. My next search result was from back in 2004:

    https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2004GL019846

    It’s pretty technical, but I think the gist is this: pan evaporation and evapotranspiration trends tend to be in a complementary relationship. The authors show this in their Figure 3. As they describe it:

    The highest values of ETpan occur at the left of the graph, in water‐limited environments, and are matched with the lowest values of ET*a. Moving to the right, precipitation increases, the water‐limitation on the evaporative process gives way to an energy‐limitation, and ETpan decreases as ET*a increases. In general, ETpan and ET*a rates converge in the wettest basins; the evaporation rate in purely energy‐limited basins is referred to here as wet environment evaporation (ETw).

    Cutting once again to the chase, the paper’s very last sentence is this:

    Although ETpan is a very useful concept, it can be misleading if used by itself to indicate climatic trends.

    Finally, I noted that the first 2 results were rather old, and even older in terms of the periods during which their data were collected: the 2004 paper considered data from 1950-2002, while the 2010 paper looked at data from 1916-2009. What does the last decade or two show?

    Good old Google Scholar allows filtering by date to find those recent studies. Result #1 was this paper from 2018, using data for Australia from 1975-2016:

    https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL079332

    Their conclusion?

    Flexible local linear regression models showed that many previously reported decreasing Epan trends have plateaued or reversed. Attribution analysis confirmed that 1975–1994 Epan decreases in southern/western Australia were chiefly driven by decreasing wind speeds. Increasing vapor pressure deficit subsequently became dominant, resulting in 1994–2016 Epan increases.

    Which ties very neatly back to what Tamino was talking about earlier.

  31. 81
    nigelj says:

    Some people appear to be thinking that climate change increases atmospheric moisture (it does ) so you get more rainfall, so less aridity so less drought. However droughts are not the same as general patterns of aridity. Droughts are more like temporary weather events where rainfall is diminished for months to a couple of years ( and are made worse by high temperatures).

    So you could have less aridity and still have more intense droughts, or more frequent droughts, if weather systems favour this and the system balances by having more intense floods somewhere in the system. This could especially be the case where you get more droughts in certain geographical regions and more floods elsewhere.

    The question is whether global warming changes weather systems predisposing things towards more droughts. It appears it will here:

    https://www.c2es.org/content/drought-and-climate-change/

  32. 82
    Mal Adapted says:

    Fred:

    Either way, it seems plausible that ACC is NOT driving climatic conditions supportive of fire, but instead is attenuating them, on balance.

    “it seems plausible”? Try that on the Australian Bureau of Meteorology:

    The dry conditions experienced over the past two years were exacerbated by record-high temperatures. Unusually warm temperatures have dominated Australia’s climate in recent years, and particularly so in the drought affected regions. Mean temperatures in 2017 (+1.53 °C) were the highest on record for the MDB to that point, with the record being broken in 2018 with an anomaly of +1.66 °C above the 1961–1990 average. 2019 is on course to approach or break the 2018 record, with an anomaly of +1.79 °C for the period from January to October. While droughts are often associated with above average temperatures, these values are typically 1 °C or more above values for previous drought years such as 1972, 1982, and 1994. High temperatures increase the stress on landscapes affected by rainfall deficiencies and add to water demand.

    IOW: according to the BOM, warming in SE Australia has made the current drought more severe (see plots at that link), leaving vegetation proportionally drier and more flammable. I’m not a recognized expert, so I’m satisfied with the BOM’s analysis. I have no reason to think they’re incompetent, or lying. Of course, deniers will keep on denying, and the willfully ignorant will stay that way. Whatever, I’m done with this topic.

  33. 83
    Fred says:

    Al #77

    Drying TREND.

  34. 84
    Fred says:

    AB #77
    Using your “Da flames” index, you would have to agree that the driest fire season on record in Australia was 1974-75, correct? Because that’s when the greatest area was burned.
    https://ro.uow.edu.au/cgi/viewcontent.cgi?article=1003&context=scipapers

  35. 85
    Al Bundy says:

    Dan H: Get off your high horse and

    AB: lower your standards

  36. 86
    Al Bundy says:

    Kevin: It’s pretty technical, but I think the gist is this: pan evaporation and evapotranspiration trends tend to be in a complementary relationship.

    AB: Excellent post. It makes sense. When it warms up plants have to protect themselves by evapotranspiration, raising relative humidity. This would suppress pan evaporation.
    ______

    nigelj: So you could have less aridity and still have more intense droughts, or more frequent droughts, if weather systems favour this and the system balances by having more intense floods somewhere in the system.

    AB: The problem is that we use the wrong metric for rainfall. “Inches” is relevant for filling reservoirs but not for ground water. “Hours” is the more important term. A light rain over a week may have fewer inches than a cloudburst but ask a farmer which s)he’d rather see.
    ______

    Fred: Using your “Da flames” index, you would have to agree that the driest fire season on record in Australia was 1974-75, correct? Because that’s when the greatest area was burned.

    AB: I said “behavior”, not “area”. Area is a somewhat random number (ignitions) multiplied by “behavior” and adjusted by lots of other stuff. You keep evading the point: fires are getting meaner because plants are struggling to pump enough water into the atmosphere to keep from overheating.

  37. 87
    Killian says:

    On resources: Skip to the end of this .pdf on simulations from the World6 model. (Yes, it’s a full-system model, update of World3, so pick through whatever else you fancy, just get over this idea resource limits don’t matter.)

    World6 model paper

  38. 88
    Killian says:

    Very simple, too simple as I can’t play with CO2 directly, thus can’t model sequestration, but if you’d like to play a bit with World3 here’s a web browser version:

    http://bit-player.org/extras/limits/ltg.html

    Go forth and find a solution!

  39. 89
    zebra says:

    #79 Kevin McKinney,

    So you think you are in a graduate seminar, and Dan H and Victor and Fred and all the others are sitting across the table from you? Seriously?

    Exactly the problem, Kevin. My opinion on this is hardly a secret; I’ve pointed out many times that you are validating the fantasy for them as well as for yourself. That’s a bad message to send to our hypothetical sincere, truth-seeking lurker.

    Where Tamino said that Dan should be boreholed, I said that the problem isn’t Dan, but rather all the people who respond to him as if there is an actual controversy/debate going on, when it is just people talking past each other, and a lot of silly rhetorical word-play.

    If you see yourself in a seminar, then I’ll be the guy at the head of the table, Professor Z, and I’m giving a bad grade. Here’s my assignment/challenge if you want to pass:

    In a debate, particularly in science, there is first a clear statement. Why don’t you tell me what you and Dan are disagreeing about, and then we’ll see if Dan will agree that that’s what you are disagreeing about. Remember, a clear statement, a sentence or two.

    We’ll proceed from there.

  40. 90
    Fred says:

    AB: “fires are getting meaner”

    By what measure are they getting “meaner”?

  41. 91
    Al Bundy says:

    AB: “fires are getting meaner”

    Derf: By what measure are they getting “meaner”?

    AB: From Siberia to Western USA to Australia to Sweden to just-about-everywhere the professionals who fight fire have all been lying about the unprecedented nature of recent fires? Oh NO! Those evil Climate Scientists have gotten to the fire fighters!!
    ______

    zebra: #79 Kevin McKinney,

    So you think you are in a graduate seminar, and Dan H and Victor and Fred and all the others are sitting across the table from you? Seriously?

    AB: I doubt it. It looked to me like Kevin was using the random BS generators who infect this room to dig into interesting stuff with the goal that he and his friends learn something. In this particular case it worked way well.

    Ya can’t teach a blockhead but you can use it for a bank shot.

  42. 92
    Fred says:

    Kevin McKinney #80

    Perhaps not though…

    You write: “[study quote] ‘Increasing vapor pressure deficit subsequently became dominant, resulting in 1994–2016 Epan increases.’
    Which ties very neatly back to what Tamino was talking about earlier.”

    I was curious to know how the authors of the above quote justified starting a new trend at the trough in the pan data (1994) and attributing it to VPD, but I couldn’t find the full study. BUT, I did find a newer 2019 study (https://iopscience.iop.org/article/10.1088/1748-9326/ab545c/pdf) which cites the Stephens et al study that you quoted above. Here’s what they found:

    “The Australia-wide pan evaporation time series shows no statistically significant change during the entire 44 year period.”

    They also looked at regional/seasonal data, and found a few statistically significant trends (as I did, and I think you did as well), but no grand picture.
    BUT, more importantly:

    “Earlier studies also found no evidence for a consistent increase in atmospheric water demand with warming, and our results both confirm and extend those studies by examining, for the first time, the autocorrelation of pan evaporation observations. Jovanovic et al (2008) showed that interannual variability in pan evaporation correlates significantly with air temperature but that correlation cannot generally explain long-term trends. *Other studies have shown that evaporative demand is more strongly driven by solar radiation and wind speed than temperature… * ”

    And this is what I’ve been saying from the beginning (although, as I said, I WAS just making an educated guess). Nonetheless, not bad for my first day, ha ha.

    The study continues:
    “…these factors [solar radiation and wind speed] do not necessarily change in response to climate change (Roderick et al 2014).”

    So, I may be wrong that ACC might attenuate fire conditions, but the study’s statement seems a little weak (“not necessarily”), so, we’ll see.

    Anyway, I am not at all convinced that Australia’s fires can reasonably be attributed to ACC. But I’m still open to good arguments.

  43. 93
    nigelj says:

    “In a debate, particularly in science, there is first a clear statement. Why don’t you tell me what you and Dan are disagreeing about, and then we’ll see if Dan will agree that that’s what you are disagreeing about. Remember, a clear statement, a sentence or two.”

    Yes, but comments are too slow to appear on this website and typical media websites for this to be fully workable. It would take 6 months to finish one discussion. So we assume people are using commonly accepted definitions etc and just do the best we can.

    If this website posted comments instantly it would help Zebras cause. So more like a chat room format.

    I tried to point out @81 that some people dont have even a basic grasp on how a drought is defined and appear totally confused about the whole aridity issue.

    And like AB says even if the discussion gets messy and at cross purposes, and the denialist is intransigent discussion can be interesting and informative for the rest of us. Have said it myself.

  44. 94
    Fred says:

    AB #91

    So, let me get this straight….
    Area burned = not scientific.
    Firefighter statements = scientific.
    Okay!!
    So, I guess the 1974-75 fires that burned 15% of Australia weren’t all that “mean”, right? Maybe we should ask the firefighters who weren’t there to compare the two.
    Good stuff!!!

  45. 95

    #92, Fred–

    Note that your more recent paper still examines pan evaporation to the exclusion of evapotranspiration, and so fails to address the argument made concerning the complementary relationship noted in the 2004 paper I cited.

    I was curious to know how the authors of the above quote justified starting a new trend at the trough in the pan data (1994) and attributing it to VPD, but I couldn’t find the full study.

    You mean you, like me, are unwilling to pay to access it! “Finding it” isn’t the problem!

    Candidly, I don’t know much about the methods of statistical “attribution analysis”, which is all the explanation the abstract gives us in reference to the issue. However, I must note that you are mis-stating the procedure to this extent: it wasn’t that the authors ‘started a new trend at the trough’; it was that the trend observable in the data changed sign. The authors’ business was to tease out *why* through the (sadly unspecified) wonders of ‘attribution analysis.’

    Your implication that there was something dodgy or underhanded in the choice of breakpoint would seem unwarranted at this point.

    Anyway, I am not at all convinced that Australia’s fires can reasonably be attributed to ACC. But I’m still open to good arguments.

    Apparently not *very* open. :-(