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Are the heatwaves caused by climate change? 

Filed under: — rasmus @ 9 August 2018

I get a lot of questions about the connection between heatwaves and climate change these days. Particularly about the heatwave that has affected northern Europe this summer. If you live in Japan, South Korea, California, Spain, or Canada, you may have asked the same question.

The raindrop analogy
However, the question is inaccurate and I will try to explain this through an analogy. Let’s say I go for a walk with a friend and my friend feels a few drops of water that fall on her. She asks me if it’s raining. But as long as there was only few drops of water, it could also be something else. 

I tell her that we can get some more relevant information in order to get a more reliable answer. Look at the sky. Are there dark clouds on the sky above? And what does the weather forecast say? 

If there are dark clouds above and the weather forecast suggests showers, it’s a safe bet to say it is the start of the rain. The rain always start with a few drops, just the way a climate change starts with a few events. 

In the same way as with the observation of the first drops of of water, you could not be sure whether the heatwave is a freak event or the emerging pattern of climate change, if you don’t include other relevant information.

There is a range of different pieces of information which are relevant when it comes to the question about weather events and climate change: (a) statistical evidence, (b) physical processes connecting different aspects, and (c) attribution work.

(a) Statistical evidence
Heatwaves are becoming more widespread, last longer, and are getting more extreme (e.g. Keellings and Waylen, 2014). This trend has been predicted and reported in multiple reports, such as the IPCC SREX (2013), the Proceedings of National Academy of Sciences (e.g. Palmer, 2009), and European Academy Science Advisory Council (EASAC, 2013). 

Climate change is equivalent to changing weather statistics, and one line of evidence includes the nature of record-breaking events. We can find evidence in both the number[a] and the magnitude of new record-breaking values.

Coumou et al., (2013) observed an increase in the global number of monthly heat records that corresponded to what one should expect if the temperatures increased everywhere by the same rate as the global mean. They also found that local monthly records are on average five times as frequent as they would be in a stationary climate. In other words, four out of five new heat records would not have occurred without global warming.

Other types of evidence includes how often the events (e.g hurricanes) take place, their duration and intensity. Standard statistical tests can also indicate whether a particular event fits in with the expected range of outcomes. 

(b) Physical processes
Physical conditions and processes play a role both for the emerging pattern of precipitation,  the evolution of weather, and their statistical characteristics. Indeed, we expect the statistics of rainfall and temperature to respond to an altered physical situation

Earth’s climate has always changed, and there have always been physical causes for the changes. This means that the climate is sensitive to altered conditions, such as greenhouse gases.

It would be difficult to explain why increased concentrations of greenhouse gases had no effect on the global mean temperature or on the statistics of  extreme weather conditions while other types of forcing clearly have an effect. 

There is no shortage on explanations for why changes in the physical environment should cause more extreme events. Some of these are:

  • Greater temperatures are expected to make heatwaves more widespread in general.
  • Weaker winds circulating the pole make weather episodes such as blocking high pressure more persistent. This weakening is associated with a polar amplification and the retreat of the Arctic sea ice (Francis and Vavrus, 2012;Coumou et al., 2015).
  • Changes in the north-south temperature differences, for instance due to the polar amplification, can increase the prevalence of the phenomenon known as “quasi-resonant planetary waves”, which is associated with heatwaves (Petoukhov et al., 2013). Mann et al. (2017) identified a specific fingerprint in the zonal mean surface temperature profile that is associated with conditions that increase the likelihood for these waves. Both the models and observations suggest that these conditions only recently have emerged from the background noise of natural variability.
  • I have also reviewed the greenhouse effect and described how convection can be altered by higher concentration of greenhouse gases. This link with the hydrological cycle may explain why the rains seem to be concentrated over small area of Earth’s surface (Benestad, 2018)

    Diminished area of precipitation explains both more frequent flooding and more droughts, and dry conditions exacerbate the heat, as moisture restrain temperatures during evaporation. 

    We also expect more extreme rainfall in some locations, as higher surface temperatures boost the evaporation and increase the turn-around rate of the hydrological cycle. There are also indications of higher cloud tops (Witze, 2016) which allow the rain drops to grow further than before.

    (c) Attribution
    It is possible to reproduce extreme weather episodes in computer models, such as those used for weather forecasting. We can conduct experiments to see which effects greenhouse gases have for the outcome. In other words, the models can be used to simulate the same event with and without the present levels (Schiermeier ,2018).

    The World Weather Attribution (WWA) has carried out such experiments, and their efforts suggest that recent extreme events have become more likely with an increased greenhouse effect.

    Individual cases and emergent behaviour of many events
    The planetary system is extremely complex, with interactions between atmosphere, oceans, ice and land, and taking place over a vast range of temporal and spatial scales.

    It is hard to say that one aspect is directly connected to another, when there are so many interacting parts and such rich level of complexity. Understanding the difference between individual versus collective events is key to making sense of the situation.

    Nevertheless, complex systems tend to give rise to emergent behaviour (explained in Gavin’s TED-talk). And the statistical characteristics of a large number of outcomes is often predictable. In fact, statistics is remarkably predictable, and we can often attribute some probability to the causes of some event through standard statistical tests.

    What is causing what?
    On another level, there is also the more philosophical question of whether rain drops are caused by the rain or the rain is a result of many rain drops. Rain is a phenomenon that includes many collective events in the clouds. 

    The same way that extra information such as cloud observation and weather forecast give confidence in our interpretation of the first drops being the start of the rain, the statistical evidence and our understanding of the atmospheric physics provide relevant information for judging the connection between heatwaves and climate change.

    A more relevant question
    I think it makes sense to rephrase the usual question of whether climate change causes a particular event, since climate and weather are different aspects of the same earth system.

    The bottom line is whether we now are observing the first glimpse of a new normal, or if the world will return to its old state. In other words, the question should be whether the recent heatwave is a signs of a new type of weather patterns we can expect for the future. I think the answer to this question is “yes”, based on current information and knowledge. 

    Footnotes

    [a] If data is independent and identically distributed (iid), then the probability of a new record-breaking event diminishes with the number of measurements (n) P(X > [x_1, x_2, ... x_{n-1}]) = 1/n. In this case, the expected number of records is E(n) = \sum_{i=1}^{n}(1/i). On the other hand, if you count many more records than E(n), then that is a sign that upper tail of the statistical distribution is stretching towards higher levels. In other words, it indicates that extremes are becoming more frequent.

    Update
    Both the World Meteorological Organisation (WMO) and Copernicus have posted some comments and analysis of the recent heatwaves.

    References

    1. D. Keellings, and P. Waylen, "Increased risk of heat waves in Florida: Characterizing changes in bivariate heat wave risk using extreme value analysis", Applied Geography, vol. 46, pp. 90-97, 2014. http://dx.doi.org/10.1016/j.apgeog.2013.11.008
    2. T.N. Palmer, "Climate extremes and the role of dynamics", Proceedings of the National Academy of Sciences, vol. 110, pp. 5281-5282, 2013. http://dx.doi.org/10.1073/pnas.1303295110
    3. J.A. Francis, and S.J. Vavrus, "Evidence linking Arctic amplification to extreme weather in mid-latitudes", Geophysical Research Letters, vol. 39, pp. n/a-n/a, 2012. http://dx.doi.org/10.1029/2012GL051000
    4. V. Petoukhov, S. Rahmstorf, S. Petri, and H.J. Schellnhuber, "Quasiresonant amplification of planetary waves and recent Northern Hemisphere weather extremes", Proceedings of the National Academy of Sciences, vol. 110, pp. 5336-5341, 2013. http://dx.doi.org/10.1073/pnas.1222000110
    5. M.E. Mann, S. Rahmstorf, K. Kornhuber, B.A. Steinman, S.K. Miller, and D. Coumou, "Influence of Anthropogenic Climate Change on Planetary Wave Resonance and Extreme Weather Events", Scientific Reports, vol. 7, 2017. http://dx.doi.org/10.1038/srep45242
    6. R.E. Benestad, "Implications of a decrease in the precipitation area for the past and the future", Environmental Research Letters, vol. 13, pp. 044022, 2018. http://dx.doi.org/10.1088/1748-9326/aab375
    7. A. Witze, "Clouds get high on climate change", Nature, 2016. http://dx.doi.org/10.1038/nature.2016.20230
    8. Q. Schiermeier, "Droughts, heatwaves and floods: How to tell when climate change is to blame", Nature, vol. 560, pp. 20-22, 2018. http://dx.doi.org/10.1038/d41586-018-05849-9

    194 Responses to “Are the heatwaves caused by climate change? ”

    1. 151
      Romain says:

      Ray Ladbury, 148: “We know what the Sun is doing. We know what the oceans are doing. We know what clouds are doing. ”

      Ray Ladbury, in the very same 148: “Please sweep up the ashes of your credibility on your way out the door.”

      Priceless…

    2. 152
      jgnfld says:

      Re. vic’s quote: “One could thus rewrite the above quote to read as follows: ‘A null hypothesis is any hypothesis generally assumed to be true until evidence indicates otherwise.’ The key phrase is ‘until evidence indicates otherwise.’ The nature of that evidence, whether it be statistical or otherwise, doesn’t really matter,”

      One can “rewrite” the definition of a “car” to read “anything which takes in fuel and can be guided by a driver to carry one or more people from one place to another.” But that would still not make a horse, or horse and buggy, a car.

      You’re just engaging in your oft-used personal version of Humpty-Dumpty again: “When I use a word,” Humpty Dumpty said, in rather a scornful tone, “it means just what I choose it to mean—neither more nor less.” “The question is,” said Alice, “whether you can make words mean so many different things.” And then you try to “back it up” by googling far and wide for one-off, out-of-context references rather than in-context, professional sources or using out-of-context quotes from wiki without any understanding.

    3. 153

      Ray, #148–

      “The LIA… well, there were changes in solar output and volcanism, none of which are occurring now.”

      I’d disagree, a bit, in that the present solar cycle was quite weak with respect to recent history at least.

      https://www.swpc.noaa.gov/products/solar-cycle-progression

      In fact, it says here: “It reached its maximum in April 2014 with a smoothed sunspot number of only 81.8,[5] the lowest since the Dalton Minimum (early 1800s).”

      But, given that GMST increased from the (weak) solar maximum in 2014, reaching a new annual record of rather stunning magnitude in 2016, it would seem that those claiming solar activity to be strongly determinative of global temperature have suffered yet another ‘own goal.’

      Prediction is hard, “especially about the future”, but “The forecasts suggest Cycle 25 might continue the declining trend of polar field decrease seen in the last three sunspot cycles, and be even weaker than Cycle 24 with far fewer than 100 spots.”

      I know of some hopeful denialati hanging their hats on that, but I think they are likely to be disappointed–especially if, as I expect, the cycle does turn out to be even weaker, and GMST continues its warming trend nevertheless. I trust Dr. Hansen’s math on that better than I trust their–well, non-math.

      And of course, none of this is entirely new:

      https://skepticalscience.com/solar-activity-sunspots-global-warming-advanced.htm

    4. 154
      CCHolley says:

      Victor @145

      From your link, it seems Curry agrees with my point of the silliness of your *null hypothesis* claims.

      Georgia Tech’s Judith Curry, the first rebutter, is having none of it. The null hypothesis that we aren’t changing the global climate is “trivially false,” she writes, and so impossible to disprove. In fact, the whole idea of a null hypothesis is pointless when it comes to attributing causation for any specific change in climate,…

    5. 155
      Victor says:

      106 Kevin McKinney says:

      *You* see no correlation. I’ve graphed the numbers previously, and I do see such a correlation.

      More importantly, standard-issue statistical measures show a correlation.

      I would suggest that the difference is in what you are prepared to see–or not see, as the case may be.

      Here’s the comparison, for 1929 to 2008 (chosen because the copy of the Law Dome data I have ends in that year, and because 80 years was specified.)

      http://i1108.photobucket.com/albums/h402/brassdoc/Law%20Dome%20CO2%20%20GISTEMP%20J-D%20anomaly.png

      V: Thanks so much for the link to this graph, Kevin, since it perfectly illustrates the dangers of evaluating data on a strictly statistical basis. Here’s a somewhat larger and clearer view of the same graph: http://photobucket.com/gallery/user/brassdoc/media/bWVkaWFJZDoxMzM1MjE5NTc=/?ref=

      The “standard issue statistical measures” you mention may indeed produce a “correlation.” But when we “eyeball” the graph with an open mind, the LACK of any correlation between 1929 and ca. 1977 becomes obvious. Nor do we see much of a correlation after ca. 1998 (the notorious “hiatus”). In fact the ONLY correlation evident to the eye lies in the 21 year period between 1977 and 1998.

      Now which do you regard as the more reliable representation of the data: that which is clearly visible to the eye, enabling you to analyze the data in some detail, taking into account ALL the information; or a single number emerging as an oracle produced from a black box that hides all the details and tells you what to think?

    6. 156
      CCHolley says:

      Victor @145

      I agree with Greg Laden’s discussion in the blog’s comments and in particular the following, which has essentially been my point:

      There can not be a null hypothesis that says “humans create climate change” or one that says “climate change is not human caused” because those two sentences are crappy hypotheses. A hypothesis has to be more refined, narrowly defined (usually) and it has to refer to specific things changing or being different under different conditions or treatments as measured a certain way.

    7. 157
      Victor says:

      139 Kevin McKinney says:

      “Victor, #–

      The notion that the Earth’s climate is now, after billions of years, controlled largely by something new (i.e., CO2 emissions) is an alternative hypothesis that requires supporting evidence.

      A serious misframing, since natural variations in CO2 have been a major control on climate over “billions of years.” In fact, that hypothesis is at least as old as the idea that human influence could affect CO2 and hence climate.

      V: OK, first of all it should have been clear that my reference to “CO2 emissions” in the above quote implied anthropogenic CO2 emissions. In the context of the Earth’s multibillion year history, naturally occurring CO2 was obviously part of what I’ve been referring to as “natural variation.”

      Secondly it’s not at all clear that naturally occurring CO2 has been a “major control” on climate in the past if by that you mean to imply that historically CO2 has functioned as some sort of “control knob” affecting global temperature. As is well known, the graph produced by Al Gore, based on Antarctic ice cores, reveals the influence of warming on CO2 levels, not the opposite, as Gore falsely claimed. Other research suggests that, over the long haul, we see little to no correlation between the two. See for example: http://c3headlines.typepad.com/.a/6a010536b58035970c017c37fa9895970b-pi

      140 Kevin McKinney says:

      “Victor, #135–

      The considerable warming trend we see in the early 20th century was primarily the result of natural forces, as CO2 levels during that period were too low to be more than a minor influence.… If CO2 were a factor we’d have seen temperatures increasingly rising over the last 120 years or so, but that is clearly NOT the case.

      OK, which is it? Was CO2 ‘too low to have an effect’ in the early 20th century? Or do we have to look for ‘increasingly rising’ temperatures ever since 1899, which would be the requisite 120 years? One can’t have it both ways.

      And it the former is supposed to be true, then I think the burden falls on Victor to specify just when the burden was no longer ‘too low.’

      V: Sorry Kevin but your point eludes me. While CO2 levels were too low to have a significant effect during the early 20th century, they were nevertheless accumulating during that period, and after 1945 they began to rise at an ever increasing rate. It stands to reason therefore that if these emissions were affecting world temperatures that would be reflected in the temperature data from the early 20th century to the present. But we see no sign of that in the actual data (as opposed to models constructed to “reveal” some sort of “underlying trend” hidden by the actual data).

      KM: (quoting Victor) There is in fact only ONE period where we see a distinct warming trend: 1979-1998. It is the effect of only these 20 years that we are really talking about when we reference “global warming.”

      KM: Very strange that the period of ‘indistinct warming’ since 1998 actually shows a stronger trend than the period of ‘distinct warming’ from 1979-1998!

      http://woodfortrees.org/data/wti/plot/wti/from:1979/to:1998/trend/plot/wti/from:1998/trend

      ’97-’98: “#Least squares trend line; slope = 0.011312 per year”
      ”98-present: “#Least squares trend line; slope = 0.0137834 per year“

      141 Kevin McKinney says:
      3 Sep 2018 at 5:29 PM
      Oh, and the 1998-present trend is *much* greater than ’79-’98 if you look at GISTEMP, rather than the WTI data I used in my first graph:

      http://woodfortrees.org/plot/gistemp/from:1979/plot/gistemp/from:1979/to:1998/trend/plot/gistemp/from:1998/trend

      Just sayin’.

      V: Here again we see excellent examples of the problem posed when we rely on trend lines cooked up by the “black box” of statistical calculation, as opposed to the more complete picture presented to the eye by the graph of the raw data. What our eyes reveal is a strong upward trend from ca. 1979 through ca. 1998, followed by a leveling off from 1998 through 2015. The spike we see in the following year is clearly an outlier, produced largely by an unusually intense El Nino, which is no secret. Whether the leap in temperature will continue in future years no one can say, so it’s misleading in the extreme to include this outlier as part of a trend.

    8. 158
      Ray Ladbury says:

      Romain, Are you claiming we don’t have a fix on total solar irradiance? On ocean temperature down to thousands of meters? On global cloud cover through satellite measurements? Seriously, mate? Are you able to claim this and keep a straight fricking face. Dude. How long did you have to practice typing this before you made it through with out giggling hysterically?

    9. 159
      Ray Ladbury says:

      Victor: “Here again we see excellent examples of the problem posed when we rely on trend lines cooked up by the “black box” of statistical calculation, as opposed to the more complete picture presented to the eye by the graph of the raw data.”

      Dude, it may be a “black box” to you. It is NOT to those of us who have actually gone to the trouble of learning statistics. An exercise to the reader, Victor. Graph the following ordered pairs:
      1,2
      2,7
      3,1
      4,8
      5,2
      6,8
      7,1
      8,8
      9,2
      10,8

      What is the nature of the function that defines the y-values? Is it linear, random, oscillatory, exponential, logarithmic…

      Now, for extra credit: LEARN WTF IS MEANT BY CORRELATION!!!!!

    10. 160
      Hank Roberts says:

      the more complete picture presented to the eye by the graph of the raw data.

      Still exercising those eye roll muscles.

    11. 161
      Jfgnfld says:

      “Our eye” reveals precisely nothing of scientific value here.

    12. 162
      Hank Roberts says:

      > unusually intense El Nino

      Unusual for the past, expected for the future.

      But Victor doesn’t see a future, just a reflection of the past.

    13. 163
      CCHolley says:

      Victor @157

      Other research suggests that, over the long haul, we see little to no correlation between the two. See for example: http://c3headlines.typepad.com/.a/6a010536b58035970c017c37fa9895970b-pi

      Interesting graph. Please link to a peer reviewed paper which contains such a graph.

    14. 164

      Victor, #155–

      But when we “eyeball” the graph with an open mind, the LACK of any correlation between 1929 and ca. 1977 becomes obvious. Nor do we see much of a correlation after ca. 1998 (the notorious “hiatus”).

      I think that statement goes a long, long way toward making my case that what you see is highly selective, particularly WRT the post-1998 period.

      In fact the ONLY correlation evident to the eye lies in the 21 year period between 1977 and 1998.

      You seem to be conflating ‘fact’ with ‘opinion’–the opinion in question being yours.

      Now which do you regard as the more reliable representation of the data: that which is clearly visible to the eye, enabling you to analyze the data in some detail, taking into account ALL the information; or a single number emerging as an oracle produced from a black box that hides all the details and tells you what to think?

      If I had to pick one, it would be normal statistical procedure every time, because as you just demonstrated for the world to see, ‘eyeballing’ is highly susceptible to bias.

      But in the real world, you don’t actually have to choose. That, one presumes, is why papers, while they hang their evidentiary hats on statistical analysis, also often provide graphic displays of evidence, too.

      IOW, that point of yours was just another big ol’ hairy straw man.

      Victor, #157–

      Look if you can’t say clearly what you mean, that is hardly my fault.

      And no, the source of the idea that carbon controls climate isn’t Al Gore; it’s been debated in the literature since 1896, and strongly accepted for something like 50 years.

      The spike we see in the following year is clearly an outlier, produced largely by an unusually intense El Nino…

      IOW, “I don’t want to consider that the warming during the latter period to be significant, so I’m going to disregard the last 3 years of data by blaming it all on El Nino.”

      That’s an excellent display of blatant rationalizing, and also of why one should in fact pay attention to impartial, pre-determined statistical analysis: you can’t fudge it; you just ‘do, or do not’.

      When one persists in ‘not doing’, it’s pretty telling.

    15. 165

      Oh, and WRT the idea that there was ‘leveling’ “through 2015” is pretty, er, dubious. Graph it, and you find that the linear trend lines is pretty much indistinguishable from the ‘distinct warming’ pre-1998:

      http://woodfortrees.org/plot/gistemp/from:1979/plot/gistemp/from:1979/to:1998/trend/plot/gistemp/from:1998/to:2015/trend

      The actual OLS numbers reveal a slightly lower warming rate, but only *very* slightly– ~0.10 C/decade, versus ~0.11 pre-’98. YMMV, but I don’t think too many folks would call that ‘leveling,’ or claim that it was particularly significant.

    16. 166
      CCHolley says:

      Victor @157

      Here again we see excellent examples of the problem posed when we rely on trend lines cooked up by the “black box” of statistical calculation, as opposed to the more complete picture presented to the eye by the graph of the raw data. What our eyes reveal is a strong upward trend from ca. 1979 through ca. 1998, followed by a leveling off from 1998 through 2015. The spike we see in the following year is clearly an outlier, produced largely by an unusually intense El Nino, which is no secret. Whether the leap in temperature will continue in future years no one can say, so it’s misleading in the extreme to include this outlier as part of a trend.

      Blah blah blah. Rinse lather repeat.

      The purpose of statistical analysis of time series is to make up for the inability of our eyes to determine trends. But, of course, Victor knows better than the experts even though he has NO formal training in statistics or science.

      And for the umpteenth time, if Victor is to say that the latest el Nino event should be ignored as an outlier, then the extreme el Nino that starts his so called leveling off period should also be ignored, which would negate the leveling off. But Victor’s purpose is to deceive rather than promote understanding. He apparently believes that if he repeats his BS over and over again that it will become true. It is tiresome.

      Stips, A. et al. On the causal structure between CO2 and global temperature. Sci. Rep. 6, 21691; doi: 10.1038/srep21691 (2016).

      https://www.nature.com/articles/srep21691

      CO2: Past, Present, & Future

      https://timescavengers.blog/climate-change/co2-past-present-future/

    17. 167

      V 157: it’s not at all clear that naturally occurring CO2 has been a “major control” on climate in the past if by that you mean to imply that historically CO2 has functioned as some sort of “control knob” affecting global temperature.

      BPL: Google “silicate-carbonate cycle”

    18. 168
      Victor says:

      156
      CCHolley says:

      Victor @145

      I agree with Greg Laden’s discussion in the blog’s comments and in particular the following, which has essentially been my point:

      There can not be a null hypothesis that says “humans create climate change” or one that says “climate change is not human caused” because those two sentences are crappy hypotheses. A hypothesis has to be more refined, narrowly defined (usually) and it has to refer to specific things changing or being different under different conditions or treatments as measured a certain way.

      V: I suggest you urge Greg to take this issue up with Kevin Trenberth, for whom “human’s create climate change” is indeed the null hypothesis. His notion of the null hypothesis is very different from the narrowly technical definition offered by so many of the amateurs posting here. That’s not to say that I agree with his rather desperate effort to reverse the null hypothesis in favor of his pet theory, far from it. For the particulars, see http://scienceblogs.com/classm/2011/11/14/what-if-climatologists-reverse/

    19. 169
      nigelj says:

      Victor is incapable of registering even obvious visual correlations, like CO2 and warming since the 1920’s, and he rejects standard, established statistical tests that also show a reasonably good correlation between CO2 and warming. He manufactures doubt for the sake of getting attention. He is not advancing discussion of anything useful.

    20. 170
      Jim Eager says:

      It’s glaringly obvious that Victor has zero training in physical science or stats.
      Enough said.

    21. 171
      CCHolley says:

      Victor @168

      V: I suggest you urge Greg to take this issue up with Kevin Trenberth, for whom “human’s create climate change” is indeed the null hypothesis. His notion of the null hypothesis is very different from the narrowly technical definition offered by so many of the amateurs posting here. That’s not to say that I agree with his rather desperate effort to reverse the null hypothesis in favor of his pet theory, far from it.

      So Victor accepts Trenberth’s notion of the null hypothesis, but rejects most everything else that he says about the area of his expertise and on the other hand rejects Judith Curry’s notion of the null hypothesis while accepting what she has to say on subjects not in her area of expertise. How convenient.

    22. 172
      nigelj says:

      https://rd.springer.com/article/10.1007%2Fs10393-018-1363-0

      New research : Climate Change and Heat-Related Excess Mortality in the Eastern USA.

      Climate change will increase extreme heat-related health risks. To quantify the health impacts of mid-century climate change, we assess heat-related excess mortality across the eastern USA. Health risks are estimated using the US Environmental Protection Agency’s Environmental Benefits Mapping and Analysis Program (BenMAP). Mid-century temperature estimates, downscaled using the Weather Research and Forecasting model, are compared to 2007 temperatures at 36 km and 12 km resolutions. Models indicate the average apparent and actual summer temperatures rise by 4.5° and 3.3° C, respectively. Warmer average apparent temperatures could cause 11,562 additional annual deaths (95% confidence interval, CI: 2641–20,095) due to cardiovascular stress in the population aged 65 years and above, while higher minimum temperatures could cause 8767 (95% CI: 5030–12,475) additional deaths each year.

    23. 173
      Victor says:

      171 CCHolley says:

      Victor @168

      V: I suggest you urge Greg to take this issue up with Kevin Trenberth, for whom “human’s create climate change” is indeed the null hypothesis. His notion of the null hypothesis is very different from the narrowly technical definition offered by so many of the amateurs posting here. That’s not to say that I agree with his rather desperate effort to reverse the null hypothesis in favor of his pet theory, far from it.

      CC: So Victor accepts Trenberth’s notion of the null hypothesis, but rejects most everything else that he says about the area of his expertise and on the other hand rejects Judith Curry’s notion of the null hypothesis while accepting what she has to say on subjects not in her area of expertise. How convenient.

      V: And YOU reject Trenberth’s notion of the null hypothesis, but accept most everything else that he says about the area of his expertise and on the other hand accept Judith Curry’s notion of the null hypothesis while rejecting everything else she has to say.

      How hypocritical.

      C’mon CC, you’re a pedant, admit it. Like so many posting here, you are so focused on your statistical computations that you’re unable to apply even the slightest bit of critical thinking to even the simplest problem. Trenberth, like so many other scientists, sees the null hypothesis the way I see it. That doesn’t mean I have to agree with anything else he’s said. Many scientists see it that way, as should be obvious by now. I don’t have to agree with Judith Curry on every issue either.

      Now put your tail between your legs and slink away.

    24. 174
      Al Bundy says:

      Victor: Now put your tail between your legs…

      AB: Disagreements essentially always end (or continue) with both sides returning home VICTORiously describing how they logically destroyed the opposition. “I knocked him out in each of the ten rounds and he never laid a glove on me!”

      (I seem to be the only human who lacks this flaw of perception.

      Signed,

      Everybody)

    25. 175
      CCHolley says:

      Victor @173

      V: And YOU reject Trenberth’s notion of the null hypothesis, but accept most everything else that he says about the area of his expertise and on the other hand accept Judith Curry’s notion of the null hypothesis while rejecting everything else she has to say.

      How hypocritical.

      C’mon CC, you’re a pedant, admit it. Like so many posting here, you are so focused on your statistical computations that you’re unable to apply even the slightest bit of critical thinking to even the simplest problem. Trenberth, like so many other scientists, sees the null hypothesis the way I see it. That doesn’t mean I have to agree with anything else he’s said. Many scientists see it that way, as should be obvious by now. I don’t have to agree with Judith Curry on every issue either.

      Now put your tail between your legs and slink away.

      Not surprising, Victor has no clue as to the difference between the two.

      And how ironic.

      The one who is ignorant of science and statistics accuses those that are actual experts of failing to use critical thinking. Unfortunately, Victor’s lack of understanding of science and statistics is only surpassed by his lack of understanding what constitutes critical thinking. The arrogance of ignorance.

    26. 176

      It is really happening. We are already seeing changes. Now its time take actions rather than debating if its real or not.

    27. 177
      Mr. Know It All says:

      The answer to the question is known with 100% certainty.

      Heat waves have occurred since humans have been able to sense them. Throughout history there have been occasional heat waves and cold spells, wet periods, dry periods, etc. Stuff happens on planets.

    28. 178
      Ray Ladbury says:

      Mr. KIA: “Heat waves have occurred since humans have been able to sense them.”

      And, Your Honor, people have been dying since time immemorial, so I should in no way be considered responsible for the victim’s death just because I shot him.

      Seriously, dude, how do you keep a straight face making such arguments. Do you, like, practice for hours in front of a mirror daily?

    29. 179
      info energie says:

      We keep repeating that as long as we do not change our vision of our consumption, natural disasters will be repeated all the time.

    30. 180

      #177, KIA–

      That’s an answer to a different question, ie., “Are *all* heatwaves caused by climate change?”

      Did you read as far as the beginning of the second paragraph?

      However, the question is inaccurate and I will try to explain this through an analogy…

      Or even to the end of the piece?

      …the question should be whether the recent heatwave is a signs of a new type of weather patterns we can expect for the future.

      It’s quite clear that your answer is not responsive to that question.

    31. 181
      Astringent says:

      KIA @177

      Stuff does happen on planets. and courtesy of science we know quite a bit about the how and why. One of the things we know is that more CO2 will make things warmer so we will experience more heatwaves.

    32. 182
      jgnfld says:

      Re. 177

      Fires have always happened. Therefore there can be no problem with intentionally lighting off a bonfire in KIA’s living room. Nor will he complain since “it’s natural”. For that matter it cannot be any problem burning down every forest on Earth. Nuclear winter is “natural” too.

      Asteroids have always collided with the Earth. Therefore there can be no problem with bending the trajectory of an asteroid to hit the Earth.

      Diseases have always occurred. Therefore eating a bunch of Salmonella can’t possibly cause any problems. It’s just “natural”.

      The “climate has always changed” argument as a reason to continue business as usual is so stupid as to be beyond belief.

    33. 183
      guidoLaMoto says:

      a) I think we can all agree that the mechanism of “GHGs” and their effect on the planet’s energy balance is correct on the qualitative level.

      b) I think it’s obvious that the correlation between co2 levels and temps can be positive or negative on very short time scales (up to ~30 yrs, are positive over the moderate time scale of the last 150 yrs or so, and neutral over very long time scales, often “lagging behind” temp changes.Keep in mind the definition of correlation lest we fall into superstitious thinking.

      c) If the GHG theory is correct, then the generally poor over-all correlation of co2:temps must mean there are other more important (in toto) factors involved in determining climate.

      From the practical standpoint, we still need to determine the quantitative effect of co2 levels on temps, and what changing temps mean to the planet in general and most importantly, to human life. All engineering solutions involve compromises between conflicting factors. It remains to be seen if lowering anthropogenic co2 emissions will have positive or negative (or any) effects on the planet in general and human life in particular, and if any benefits outweigh any costs.

    34. 184

      gLM, #183–

      I think it’s obvious that the correlation between co2 levels and temps can be positive or negative on very short time scales (up to ~30 yrs, are positive over the moderate time scale of the last 150 yrs or so, and neutral over very long time scales, often “lagging behind” temp changes.

      Oh, really? Can you point to even one ‘negative correlation’ between CO2 and ‘temps’?

      Unless you can, I think it’s obvious that you don’t know what you are talking about.

    35. 185
      Hank Roberts says:

      c) If the GHG theory is correct, then the generally poor over-all correlation of co2:temps must mean there are other more important (in toto) factors involved in determining climate.

      Nope. It’s a commonly rebunked talking point to claim “anything but CO2” because the steady increase in CO2 doesn’t produce an equally steady change in climate — ignoring the variability of climate and weather.

    36. 186
      Hank Roberts says:

      https://www.giss.nasa.gov/research/briefs/lacis_01/

      Science Briefs
      CO2: The Thermostat that Controls Earth’s Temperature

      By Andrew Lacis — October 2010

      A study by GISS climate scientists recently published in the journal Science shows that atmospheric CO2 operates as a thermostat to control the temperature of Earth.

    37. 187
      Mal Adapted says:

      guidoLaMoto

      It remains to be seen if lowering anthropogenic co2 emissions will have positive or negative (or any) effects on the planet in general and human life in particular, and if any benefits outweigh any costs.

      Ah, another lukewarmer who ignores the toll that AGW is already taking, not just on “the planet in general” but in particular human homes, livelihoods and lives. OTOH, it’s clear that the costs, and the benefits, of the ongoing anthropogenic transfer of fossil carbon to the atmosphere are unevenly distributed among particular humans. As lukewarmers do, guidoLaMoto presumably expects his personal benefits to outweigh his costs. I wonder who pays for disaster relief in his country?

      No, it does not “remain to be seen” that anthropogenic co2 emissions is having negative effects! Furthermore, it’s trivial to project that continued large-scale anthropogenic transfer of fossil carbon to the atmosphere will have increasingly negative effects. It’s not reasonable, therefore, to assert that no collective (i.e. government) action to reduce emissions will result in lower net aggregate cost. Of course, there are more wrong ways than right ways to do it, but that’s true of all collective actions. It’s one reason why dramas of the Commons are so often tragic! Nevertheless: without some kind of collective intervention, a global Tragedy of the Climate Commons is inevitable.

      Your best defense against a net-negative personal outcome, guidoLaMoto, is to support a revenue-neutral US Carbon Fee and Dividend with Border Adjustment Tariff. In any case, though, why should anyone pay for your private fossil carbon emissions but you?

    38. 188
      Ray Ladbury says:

      GuidoLaMoto,
      a) What do you mean “qualitative”? How would you have a qualitative correlation if you didn’t have quantitative correlation?
      b) No. The correlation is actually quite good.
      c)Again. The correlation is actually quite good

      You really should look into the facts before posting here and making a fool of yourself.

    39. 189
      Marco says:

      @183 Your points b and c suggest to me that you don’t quite know what climate scientists have already predicted decades ago. Climate scientists predicted, before it was observed, that in the ancient past there should be lags, at least on Antarctica, between temperature increase and CO2 increase. The fact is that we cannot explain the continuing increase in temperature after the initial increase due to the relevant Milankovitch cycle *without* CO2 increase. We also cannot explain why the lag is reversed in the Northern Hemisphere, without the impact of CO2 on temperature. Neither can we explain most of the increase in temperature over the last 150 years without CO2 increase.

      The consilience of evidence for the primary impact of increased CO2 concentrations on the temperature increase of the last 150 years is overwhelming. It appears your doubt is primarily caused by your distaste of the proposed solutions.

    40. 190
      Carrie says:

      188 Ray Ladbury says:
      22 Sep 2018 at 11:43 AM

      GuidoLaMoto,
      a) What do you mean “qualitative”? How would you have a qualitative correlation if you didn’t have quantitative correlation?
      b) No. The correlation is actually quite good.
      c)Again. The correlation is actually quite good

      [EDITED Retort from the book “How to win friends and influence People.”]

      Hello there Guido, I think you’re new here. I’d like to help you out because it is quite possible something has confused you about the science that underpins those points above. I’d be happy to help if you like.

      It’s a really complex and complicated issue this global warming business and everyone finds it hard to get their head around it usually, especially when they are first looking into it. So if this is you, feel free to get back to me and one of the other regulars here who are quite experienced & knowledgeable about eh intricate details of the evidence. Many have a good background in science in various fields. There’s also many links here to good basic info I could point you too, that may help.

      Best to you either way, Ray.

    41. 191
      zebra says:

      #188 Ray Ladbury,

      “qualitative” and “quantitative”

      Guido is pretty likely trolling Denialist, but this is one of those terminology things I think would be helpful for people to use consistently.

      Saying “the temperature is going up” (or down, or constant) is qualitative. And it is important to point out, when people complain about the spread of model predictions, for example, that the qualitative match with observation (going up!) is a strong validation of the underlying theoretical foundation– even if the quantitative (numerical) match doesn’t seem that close.

      I’m guessing that if you get a response from GLM (unlikely) it will be a repetition of the usual trend cherrypicking and magical “other causes”.

    42. 192
    43. 193
      guidoLaMoto says:

      period of negative correlation? Try ~1960-1985. Try to keep up. I don’t think they’ve adjusted the data quite that much yet to erase that cooling.

      Theory: I have the chills, so I turn the thermostat up to 78. My computer model says the house should warm up to that.

      Reality: I turn the thermostat up to 78, but my menopausal wife opens the window as they place warms up. The house doesn’t get much warmer.

      It’s never a good idea to argue religion, so I’ll depart. Sorry if a put a rumple in your bubbles.

    44. 194

      #193, gLM–

      1960-1985, for an example of ‘negative correlation’?

      Oh, sorry, I thought you meant something long enough that it might actually be meaningful. But what the heck? I’ll play.

      So, here’s 1960-85 temps, graphed against CO2:

      http://woodfortrees.org/plot/gistemp/from:1965/to:1980/plot/gistemp/from:1965/to:1980/trend/plot/esrl-co2/from:1965/to:1980/offset:-330/scale:0.02

      “Negative correlation?”

      Just Mark I eyeball, but I’m not seeing it…