Monthly Archives: May 2015

The Magnificent Seven Nobel Laureates of Bjorn Lomborg

Bjorn Lomborg often touts, and has done so recently, that his Copenhagen Consensus Center works with seven Nobel Laureates. I’ve always let that pass but wondered if it was really true, who they were, and what that involvement consisted of. Graham Readfearn of DeSmog Blog has done the hard work of running this down and he found out that this is not as impressive as it seems. For one thing, one of the Seven is not actually alive. Of the other six, at least one is a very well known climate change contrarian, and overall the amount of work, and the quality of the work, they have produced is unimpressive.

Check out: “Seven Nobel Laureates” Behind Climate Contrarian Bjorn Lomborg’s Think Tank Are Not All They Seem, Or Even All Alive

Here is a meme I made to commerate Graham’s efforts:
Screen Shot 2015-05-26 at 11.07.30 PM

Click the image to get the full size original.

Click here to learn more about Lomborg.

What happened to the dinosaurs?

Did you ever wonder? And if you did wonder, did you Google it? And if you did google it, did you get the results shown above? And if you did, did you click “feedback” and do something like the following?

Screen Shot 2015-05-26 at 2.02.10 PM

No? Do so now, please.

This is important. Why? Because we have been hearing rumors lately that Google intends to change the way it produces searches to bias the search results in the direction of more reliable sites. But the number one search result for a key question that a lot of people ask about evolution is a bogus creationist site.

I’ve never, for one moment, gone along with the idea that Google can pull off a better, more reliable search based on the Google view of what sites are more reliable. My position on this has annoyed many of my colleagues. The promise of the Internet being less bogus and more educational is attractive. But it is a siren call. Regarding this particular issue I’ll claim the role of Galileo until proven otherwise.

Screen Shot 2015-05-26 at 9.57.27 PM

Also of interest: In Search of Sungudogo: A novel of adventure and mystery, set in the Congo.

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    Heat And Death In India: Global Warming’s Direct Effect

    The Earth is warming because of what humans have been doing to the atmosphere. Global Warming has a lot of effects many of which we’ve discussed here, but the most obvious one is, well, it gets warmer. At present, India is experiencing record breaking heat and people are dying.

    It is very difficult to say how many people die from the heat in any region. We can use a standard approach used by epidemiologists to estimate this number. This involves simply looking at mortality rates as they change over time to try to detect a signal, an increase, associated with the variable in question. If all sources of mortality remain the same over a period of time, but a heat wave occurs during that period and with it comes an increase in mortality, then it is possible that those extra deaths are due to the heat. Nothing, of course, is that simple, but epidemiology has some fancy tools to try to tease out reasonable numbers.

    I’m reminded of the Ituri Forest, where I worked for a few years. We kept track of births and deaths, and it became apparent that deaths tended to be seasonal. More people seemed to die during the annual “hunger season.” This season occurred around June, when the first wet season crops (there are two wet seasons) were not ready, and the previous wet season’s crops were mostly used up. At the same time, other crops were not abundant and wild foods (both plants and animals) tended to be hard to come by, as the forest experienced a coeval reduction in productivity of human edible foods. But the people who died during that period rarely seemed to die of hunger. They died of other things, such as infectious disease, but presumably these other causes of mortality were more effective when combined with food stress. One hunger season, two people died in a murder-suicide. An elderly couple lived in a small village, alone, with an orphaned grandchild. It was a bad hunger season for them since their village lacked the resources to produce enough food. It is believed the elderly woman, depressed by the hunger, harvested poisonous wild yams and made a meal of them, knowingly, and fed them to her family. She and her husband died, but the child vomited up the deadly meal and survived. Those were hunger-related deaths, but as is the case with many such deaths, were embedded in a much more complicated scenario.

    Right now people in parts of India are dying of the heat, but many more than those known to die of heat stroke are also dying in this more complicated way. Indian heat waves are increasing in their frequency, being one third more common by the end of a study period covering 1961-2010, according to a 2014 study. The problem has become worse due to anthropogenic global warming, and it is made even worse in El Niño years. And, we seem to be entering an El Niño period. Changes in land use and urbanization are also probably contributing factors in India.

    Heat wave related death spells produce numbers in the hundreds. Something like 500 people are known to have died directly of the heat over the last few days in India. But other deaths caused by multiple factors where heat is a sort of final straw would be in the thousands.

    Right now, India is very hot, and some areas are expected to become even hotter over the next several days.

    Fred Barbash at the Washington Post has a good writeup on the current situation there.

    UPDATE: Jeff Masters has a current write-up of the heat wave in India. At present the death rate (which is certainly an underestimate) for India places it fifth in known historic deadly heat waves.

    Arctic Sea Ice Decline in 2015

    The surface ice in the Arctic has been melting to historic low levels every year for the last several years. The graph above shows the first ten years in the National Snow & Ice Data Center records, meant to indicate what Arctic Sea Ice “normally” does as it melts off during the northern warm months. The thick black line is the average over 1981-2010, and grey shaded area shows two standard deviations above and below that line. The blue line tracking along the lower end of the 2SD shaded area is the ice extent this year. During the period when sea ice is at its maximum, this year’s ice was low. This does not reliably predict the ultimate September minimum, but it is interesting that the sea ice extent is following an extreme course.

    I’m reluctant to say anything about what will happen this year. The melting rate could slow, storms that may play a role in diminishing sea surface ice in the Arctic may not play a big role. Or, the rate of melt could increase and all the various factors that determine a year’s minimum could drive the ice off the sea to the extent that we have a record low. It would be very hard to beat the 2012 minimum extent, as that was an extreme year. But, that extreme year, show on the figure below, was not as low at the present time as the current extent.

    Screen Shot 2015-05-26 at 12.22.18 PM

    The volume of sea ice is in some ways more important than the area it covers, because this reflects the overall Earth’s surface heat imbalance resulting from the human-induced greenhouse effect. Volume includes both new ice (formed over the previous winter) and old ice that does not melt at all in a given year. This old ice probably serves the role of keeping some of the new ice stable so it melts less, so there is a feedback. The more the volume reduces, the more the surface area may reduce, depending on various conditions.

    Andy Lee Robinson has created, and regularly updated, an amazing graphic showing the change over time in Arctic sea ice volume.

    Hurricanes in the Eastern Pacific: 2015 UPDATE

    See below for update.

    You may not have even noticed it, but hurricane season has officially started in the Eastern Pacific. That is because the official date of the start of season is May 15th, though the actual hurricanes rarely get the memo and start whenever they want, but usually after that date. Last year’s Eastern Pacific season was much ore active than usual. The average numbers for named storms, hurricanes, and major (above Cat III) hurricanes for this basin are 15.4, 7.6, and 3.2. Last year’s season was predicted to be pretty much average, but it turned out to be exceptional, with 22 named storms, 16 hurricanes, with 9 major. In addition, there were other notable features such as several storms forming early, two early storms reaching Cat 4 strength, and one storm being the strongest ever recorded in May in the region.

    What about this year? The only prediction I’ve seen suggests a somewhat more than average season (19 named storms, 11 hurricanes, with 4 major). So far there are no named storms, but there is one disturbance that is likely enough to turn into one that I thought this would be a good moment to start paying attention, thus this post.

    The stormy system is currently known as Disturbance #1, and it is sitting in the pacific south of Mexico. The National Weather Service calculatges a 20% chance of this disturbance becoming a tropical cyclone over the next 48 hours, but an 80% chance over the next 5 days.

    If Disturbance #1 becomes a named storm, it will be christened “Andres,” a previously unused name.

    Fewer hurricanes that form in the Eastern Pacific hit land than for most other basins, and they very rarely hit the US or Mexico.

    UPDATE (27 May 1:51 Central)

    Disturbance 1 is developing. The National Weather Service says this disturbance has an 80% chance of forming a tropical cyclone over the next 48 hours, and a 90% of doing so over the next five days. Again, it will be named Andres if it becomes a named storm. Here’s what the region looks like (The red X is Disturbance 1):

    Screen Shot 2015-05-27 at 1.51.11 PM

    Screen Shot 2015-05-27 at 1.53.49 PM

    UPDATE (28 May 12.27 Central)

    Andres is a named tropical storm.

    Star Wars Fan Film: The Recompense

    I’ve written about The Recompense here, and that writeup includes interviews with the creative team putting the film together. This is just a quick note to remind you that The Recompense has a kick starter project with one week left. So, now, you have to go there and kick in a few bucks!

    The graphic above is the budget breakdown for the film, indicating what has already been invested and what the Kickstarter campaign will fund. Here is a note from the film’s team:

    With just over one week left in our campaign, we wanted to show you how your contributions, if our project is successfully funded, will affect the production of our film.

    Your support enables us to finish building our sets, create the first ever live-action Bothan, bring practical, tangible effects to the film, and provide comfort and a place to rest for our cast and crew to stay in top shape throughout the production of the film.

    In order to make this project a reality though, we need your support now more than ever, as we enter into our final week tomorrow.

    Spread the word on social media, and share our page with friends and family. Chances are, someone you know is a Star Wars fan! Show them what we’re trying to accomplish, and encourage them to contribute even as little as $1. The more backers we have, the more popular our project becomes, and the better chance we have of bringing this tribute to Star Wars to life, and having you all along for the ride.

    Remember – if our project does not reach it’s fundraising goal, we receive none of the funds, and this film can’t be made.

    Strap yourselves in…. Time to make the jump to lightspeed.

    – The Recompense Team

    So, here is the kickstarter you are looking for.

    California Drought Caused By Climate Change

    Human released greenhouse gas pollution changes the climatic system through a variety of mechanisms. Trade winds and jet streams change their patterns of movement, and the distribution of moisture in the air changes, with precipitation either lacking more than usual or being more abundant than usual. The patterns of movement of major air masses and the increased bifurcation of air masses into more wet than usual and more dry than usual can result in long periods where region experiences excess precipitation or a lack of precipitation. When the latter happens, there can be a drought.

    Increasingly, the California drought is being seen as an effect of climate change. Air masses that should have contributed precipitation in the form of mountain snow, which in turn feed the western ground water system, have been kept away. Increased temperature has increased evaporation. Other factors related to climate change have contributed. The result is an historic drought over California that shows at present no sign of stopping any time soon. There was hope that last winter there would be additional precipitation, and there was some, but not enough.

    A paper just out in Geophysical Research Letters uses modeling and historic data to confirm that the current California drought is very likely an effect of climate change. The paper is “Temperature Impacts on the Water Year 2014 Drought in California“, by Shraddhanand Shukla, Mohammad Safeeq, Amir Aghkouchak, Kaiyu Guan, and Chris Funk. Here is the abstract, which is pretty self explanatory and understandable:

    California is experiencing one of the worst droughts on record. Here we use a hydrological model and risk assessment framework to understand the influence of temperature on the water year (WY) 2014 drought in California and examine the probability that this drought would have been less severe if temperatures resembled the historical climatology. Our results indicate that temperature played an important role in exacerbating the WY 2014 drought severity. We found that if WY 2014 temperatures resembled the 1916-2012 climatology, there would have been at least an 86% chance that winter snow water equivalent and spring- summer soil moisture and runoff deficits would have been less severe than the observed conditions. We also report that the temperature forecast skill in California for the important seasons of winter and spring is negligible, beyond a lead-time of one month, which we postulate might hinder skillful drought prediction in California.

    The caption for the graphic above is: “Percentiles of potential evapotranspiration (ETo) during WY 2014 with respect to 1979 to 2012 climatology.”

    I find the ancillary finding of the lack of skill of temperature forecasts in California. One would expect low skill in forecast models that are designed under a given climatology, when that climatology shifts as it seems to have done.

    New Research: Antarctic Glaciers Destabilized

    A large portion of the glacial mass in Antarctic, previously thought to be relatively stable, is now understood to be destablizing. This is new research just out in Science. The abstract is pretty clear:

    Growing evidence has demonstrated the importance of ice shelf buttressing on the inland grounded ice, especially if it is resting on bedrock below sea level. Much of the Southern Antarctic Peninsula satisfies this condition and also possesses a bed slope that deepens inland. Such ice sheet geometry is potentially unstable. We use satellite altimetry and gravity observations to show that a major portion of the region has, since 2009, destabilized. Ice mass loss of the marine-terminating glaciers has rapidly accelerated from close to balance in the 2000s to a sustained rate of –56 ± 8 gigatons per year, constituting a major fraction of Antarctica’s contribution to rising sea level. The widespread, simultaneous nature of the acceleration, in the absence of a persistent atmospheric forcing, points to an oceanic driving mechanism.

    The paper is “Dynamic thinning of glaciers on the Southern Antarctic Peninsula” by B. Wouters, A. Martin-Español, V. Helm, T. Flament, J. M. van Wessem, S. R. M. Ligtenberg, M. R. van den Broeke, J. L. Bamber.

    Here is a simulation of grounding line retreat in action from NASA:

    Karl Mathiesen at the Guardian has a writeup on the research here.

    The sheet’s thickness has remained stable since satellite observations began in 1992. But Professor Jonathan Bamber of Bristol university, who co-authored the study, said that around 2009 it very suddenly began to thin by an average of 42cm each year. Some areas had fallen by up to 4m.

    “It hasn’t been going up, it hasn’t been going down – until 2009. Then it just seemed to pass some kind of critical threshold and went over a cliff and it’s been losing mass at a pretty much constant, rather large, rate,” said Bamber.

    The estimate of ice loss by this research might be overestimated, according to Andrew Shepherd, who notes that some of the thinning of the glacier could be due to changes in snowfall amounts on tip, rather than melting from the bottom. It will be interesting to see how this works out.

    Caption for the figure at the top of the post:

    Fig. 2 Mass variations for the sum of basins 23 and 24, as observed by GRACE and modeled by RACMO2.3.
    Basins 23 and 24 are defined in (21, 22). The faint blue dots are the monthly GRACE anomalies with 1? error bars (20), and the thick blue line shows the anomalies with a 7-month running average applied so as to reduce noise. Cumulative SMB anomalies from RACMO2.3 are shown in red, with the light red area indicating the 1? spread in an ensemble obtained by varying the baseline period (20). The dashed light blue line shows the estimated dynamic mass loss (GRACE minus SMB). The vertical dashed lines indicate January 2003, December 2009, and July 2010, the start and ending of the different altimetry observations. (Inset) The GRACE time series for the individual basins 23 (blue) and 24 (red), before (full lines) and after (dashed lines) applying the SMB correction.

    State Of Emergency in California

    Governor Jerry Brown has declared a state of emergency for the Santa Barbara oil spill. Phyllis Grifman, associate director of the USC Sea Grant Program, is quoted i a a University of Southern California press release as saying, “Nothing worked – they found out about this because people camping nearby or living nearby smelled it. Nothing happened on the part of the infrastructure that could shut it down early.” The spill, she notes, sits beteween two areas under protection for endangered marine wildlife. Taj Meshkati, also a USC professor (of engineering) asked, “Why did it take the company so long to detect and stop the leak? This points to an important human problem in the safety culture issue.” Raj Rajagopalan of USC’s Marshall School of Business, an expert on supply chain management, notes “This spill will have an impact on the local tourism industry given that the sight of oil on its pristine beaches does not help and also on local fisheries. There will be a spillover effect from the tourism impact on other local business. But I anticipate that the effect on the economy will be short-term (a few weeks) because the spill is not very large and so hopefully it will be contained soon.”

    Governor Jerry Brown is quoted in the BBC as saying he state would “quickly mobilise all available resources. We will do everything necessary to protect California’s coastline.”

    The spill is believed to have put about 21,000 gallons of oil in the ocean.

    The risk of hot and cold weather

    A new paper is just out in The Lancet that examines the mortality risk of high and low ambient temperatures. The basic idea is that if it is either to hot or too cold, mortality may increase, possibly with the weather being a factor to augment the effects of other health problems, or as a direct result. The paper is methodologically reasonably well done but leads to conclusions that I think will be misinterpreted and misused. The paper implies that a shift to a warmer world would have lower mortality effects than a shift to a colder world might. Or, more significantly, that a shift to a warmer world will reduce ambient temperature related mortality by reducing the effects of cold. This is incorrect for a number of reasons.

    Having said that, this paper does make a valuable contribution to public health, though here I’ll note that only in passing (see below).

    First, I’ll give you the author’s viewpoint directly by quoting from the abstract, then I’ll tell you what I think about it.

    The paper is “Mortality risk attributable to high and low ambient temperature: a multicountry observational study,” by Antonio Gasparrini and a host of other authors. It says:

    Background Although studies have provided estimates of premature deaths attributable to either heat or cold in selected countries, none has so far offered a systematic assessment across the whole temperature range in populations exposed to different climates. We aimed to quantify the total mortality burden attributable to non-optimum ambient temperature, and the relative contributions from heat and cold and from moderate and extreme temperatures.

    Methods We collected data for 384 locations in Australia, Brazil, Canada, China, Italy, Japan, South Korea, Spain, Sweden, Taiwan, Thailand, UK, and USA. We fitted a standard time-series Poisson model for each location, controlling for trends and day of the week. We estimated temperature–mortality associations with a distributed lag non-linear model with 21 days of lag, and then pooled them in a multivariate metaregression that included country indicators and temperature average and range. We calculated attributable deaths for heat and cold, defined as temperatures above and below the optimum temperature, which corresponded to the point of minimum mortality, and for moderate and extreme temperatures, defined using cutoffs at the 2·5th and 97·5th temperature percentiles.

    Findings We analysed 74225 200 deaths in various periods between 1985 and 2012. In total, 7·71% (95% empirical CI 7·43–7·91) of mortality was attributable to non-optimum temperature in the selected countries within the study period, with substantial differences between countries, ranging from 3·37% (3·06 to 3·63) in Thailand to 11·00% (9·29 to 12·47) in China. The temperature percentile of minimum mortality varied from roughly the 60th percentile in tropical areas to about the 80–90th percentile in temperate regions. More temperature-attributable deaths were caused by cold (7·29%, 7·02–7·49) than by heat (0·42%, 0·39–0·44). Extreme cold and hot temperatures were responsible for 0·86% (0·84–0·87) of total mortality.

    Interpretation Most of the temperature-related mortality burden was attributable to the contribution of cold. The effect of days of extreme temperature was substantially less than that attributable to milder but non-optimum weather. This evidence has important implications for the planning of public-health interventions to minimise the health consequences of adverse temperatures, and for predictions of future effect in climate-change scenarios.

    What could possibly go wrong?

    Obviously, the main way this paper could derail is when climate change denialists make the claim that global warming is good because cold weather causes more mortality than warm weather, so we’ll have less mortality. This, however, is incorrect for several reasons.

    Assume the paper has correctly characterized mortality effects of weather. From this we assume that there is a certain mortality profile with temperature as the cause. Medium temperatures don’t exacerbate population level mortality but above and below that, mortality increases. This is expected for any species where temperature matters. Key life history traits including maintainance (and thus, basic survival) may be linked to temperature, and if temperature is too high or too low, things go badly. The problem with the assumption that increasing temperatures will decrease mortality is that the more logical interpretation, which fits with what we know about the biology of warm blooded animals, is that any change, up or down, in the range and average of temperatures will have negative effects. In other words it is incorrect to assume that since there is less mortality at the upper end of the range that heading for that direction is good. There is increased mortality at both ends, movement in either direction should be assumed to increase mortality in that direction.

    One result of the paper, only briefly touched on but clear from the data, is that the lower end of ambient temperature mortality effects has a long distribution, while the upper end (warmer temperatures) have a lower end. This means that the two phenomena, too cold and too warm, have different statistical characteristics. For this reason, comparing the two is a rather dicy affair. It is like comparing the negative effects of driving too slow and driving too fast. Either one can mess you up on the highway, but there is a lot more room at the lower end. Where the speed limit is 60, a very very fast speed is 20 miles an hour faster, but a very very slow speed might be 50 miles an hour slower. Not only are the statistics very different (and thus not comparable between the two ends) but the mechanisms are different. With respect to temperature, colder conditions probably exacerbate mortality by requiring that the body spend more energy on maintenance, thus taking away energy from immune response. At the upper end, added heat does something entirely different, requiring an entirely different mechanism (cooling) to kick in, and in more extreme cases, causing a direct pathological outcome, heat stress.

    Human Evolution

    I think it is helpful to put this paper in evolutionary context. Humans are primates, and as such, evolved in the tropics. We evolved, in other words, at the higher end of the temperature range discussed in this study, and should be adapted to warm conditions. Humans are hominoids (apes) which, among primates, evolved in the warmer end of that range, with extra humidity. We are hominins, a special kind of ape, that extended its habitat to include somewhat (but not too much) drier conditions. When our genus arose, we began to spread into novel habitats, including some that were cooler, but for nearly two million years various human ancestors were limited to tropical or sub tropical conditions. It was not until our species evolved that we fully adapted to the full range of conditions from very cold to very warm, from very dry to very wet. Indeed, technologically modern humans who rely on agriculutre have been excluded from the most extreme environments our foragering ancestors occupied thousands of years ago, and adapted to both physically and culturally.

    In other words, from our evolutionary history we would predict that humans would suffer relatively low levels of heat related mortality and high levels of cold related mortality, and that many of our more recently developed, and limited, adaptations are to cold while our deeper and longer-term adaptations are to heat. We may even walk upright because of heat (that is one theory that has never been tossed out to explain why a chimp-like ancestor was selected to become more upright). Modern humans mostly have the physical form of a tropical African because we mostly come fairly recently from tropical Africa. Our heat related adaptations tend to be physical, long-evolved, built in. Our cold adaptations (with a few exceptions) tend to be cultural, technological, added-on. The range of temperatures that actually occur on Earth that heat stress us is limited, the range of temperatures that actually occur on Earth that cold-stress us is very large.

    Our evolutionary biology predicts that we would have a higher mortality rate under cold than under heat, and this paper confirms that.

    This isn’t your great great great great grand daddy’s planet

    The problem arises when we leave the Earth in which we evolved and arrive on a hot new planet. Most of the physical evolution (our exact ratio of body parts, our respiratory adaptations, skin and hair related adaptations, fat distribution, etc.) and our cultural adaptations (fire, clothing, shelter, mobility, diet) that related to temperature, cold or hot, arose over the last two million years, which is coincident with the Pleistocene. During this period atmospheric CO2 levels ranged around an average of about 250ppm, rarely going above 300ppm, and never approaching 400ppm. CO2 levels correlated well with the surface temperatures in which we live, and the current atmospheric CO2 level is 400ppm and rising. It will take time (a few more decades) for the new temperature regime, the one human greenhouse gas pollution is causing, to be realized. But when that happens we’ll be living on a planet with temperature characteristics not seen during the entire course of human evolution. Some regions will have temperature ranges that go well beyond the ranges explored in this paper. Extrapolating the effects of high ambient temperatures from the last several decades to the middle of the 21st century is difficult at best.

    Normal human body temperature is 98.6 degrees F. That is higher than the average daily temperature for most places humans have lived over the last 2 million years, but within the range of the highest daily temperatures. The problem is, when ambient temperatures are higher than this amount, our brains are at risk, and cooling adaptations have to kick in. If average ambient temperatures in a warm region go too high, these adaptations will not be adequate, and heat spells may become routinely fatal. If, on the other hand, in other regions of the world, average ambient temperatures went way down (like, if Florida became like Minnesota) we would adapt by changing the geographical distribution of the use of existing and well established technologies.

    Putting this another way, humans can adapt, and in the past have adapted, to cooling. We can not adapt, in the warmest regions, to heating. There is not a mechanism that allows this, and there is no practical technology other than air conditioners, and it is not really practical, ore even possible to create air conditioners that would allow survival in tropical regions for anyone other than the elite and ex patriots.

    Another factor, already implied above but I’ll underscore it, is the fact that moving towards warmer conditions does not remove colder conditions. The mortality induced by cooler ambient temperatures discussed in this paper is not from people freezing to death on ice flows. It is from ambient temperatures mostly above freezing, which in the absence of a technological fix, cause added stress. Even with increased surface temperatures caused by global warming, these conditions will still persist. The range of temperatures over which this cold induced stress occurs is, as stated, very large and even if overnight temperature minima rise with global warming in a given region, most of those temperatures will still be regularly represented.

    From the paper:

    Despite the attention given to extreme weather events, most of the effect happened on moderately hot and moderately cold days, especially moderately cold days. This evidence is important for improvements to public health policies aimed at prevention of temperature-related health consequences, and provides a platform to extend predictions on future effects in climate-change scenarios.

    This is an important and valid point. This cold related mortality can be addressed with some simple technological fixes, including even a modest amount of insulation or other improvements in constructions in homes in tropical or subtropical areas where it is warm enough that many people at the lower end of the socioeconomic spectrum (i.e., almost everybody) does not typically bother with such things. This is an important result of the paper that has nothing to do with global warming but should be paid attention to.

    A potential bias

    The paper relies on mortality data for cold vs. hot ambient temperature periods. However I question the ability to obtain data on heat related deaths that are comparable to cold related deaths. In the more extreme cool areas, the northern countries, there are good data on mortality. In the more extreme warm areas, along the equator, the mortality data one would ideally use are virtually non existent. Of the seven billion people who live on the earth, the one billion that are most unlikely to show up in any systematic data of any kind live along the equator, and very few (some reindeer herders in Siberia, for example) live in the cooler climates. I don’t think the authors address this kind of bias adequately.

    It’s about time

    The study period ranges from the 1980s to recent. This is the period of time during which about half of the surface warming experienced during the 20th century has occurred, and at a high rate. The authors do not examine change over time in mortality at either end of the temperature range. Since the key variable, ambient surface temperature, changes dramatically over the study period, this should have been addressed. It may be that due to the nature of the data this could not be done, but the paper explicitly makes assertion about change over time in the future without addressing change over time during the study period. This makes me sad.

    In summary, shifting to a warmer world will have more negative effects than shifting to a cooler world, when it comes to human health related response to ambient conditions. The paper implies that warming is not as bad as cooling might have been, and this will be used by those who deny the very existence of, or human fingerprint on, or importance of, or ability to address, climate change. The paper lacks contextualization of the problem in terms of well known human adaptations. There may be significant biases or problems with respect to reported mortality an change through time during the study period in the key variable, ambient surface temperature.