Commentary: Follow the Evidence on Climate Impact
By Scott Hastings Texas Medicine September 2020

Sept_20_TM_Commentary_HastingsI read with interest the article, The Temperature’s Rising” in the May 2020 issue of Texas Medicine. The article features Robert Haley, MD, a Dallas epidemiologist, in his quest to educate the public about the harmful effects of climate change. Dr. Haley implores us to “focus on what the evidence shows.”1 I couldn’t agree more.

While the World Health Organization estimates that climate change will cause approximately 250,000 additional deaths per year worldwide from malnutrition, malaria, diarrhea, and heat stress, these estimates are based on assumptions using models that have not been validated using real world, observational data.

If we look strictly at observational rather than modeling studies, we get a different picture of the data. In the face of a gradually warming climate, it appears that worldwide malnutrition, malaria, diarrhea, and heat stress are, in fact, decreasing over time. For example, hospitalizations and mortality for malnourished children appear to be declining in vulnerable countries,2 especially in children under 5 years old.3  Additionally, malaria infections have been trending down as well.4

If we look at the common causes of diarrhea, namely E. coli and salmonella, we find studies of either stable or decreasing incidence trends over time,5,6 and another study even suggests temperature has no bearing on cholera incidence, as it’s incidence has also been decreasing over time.7

If we look at heat stress, including heat related mortality, research points to just the opposite of what we have been warned by Dr. Haley. In fact, heat related illness and death has plummeted in the U.S. and elsewhere over the past several decades, despite a gradually warming climate. In the United States, the number of heat related hospitalizations, specifically in the elderly, have decreased very significantly in recent decades.8 This phenomenon is not isolated to only the United States. Europe has also enjoyed decreasing heat-related morbidity and mortality.9,10 In fact, a meta-analysis in 2018 of 71 studies reveals an overall decrease in sensitivity to excessive heat over the past 2-3 decades.11 Additionally, it comes as no surprise to most epidemiologists that more deaths occur during cold winter months, than in warm summer months.

According to the Texas Medicine article, climate change has been blamed for contributing to the severity of weather and health events, including the 2011 statewide drought, the 2012 outbreak of West Nile in Dallas, Hurricane Harvey in 2017, and increasing prevalence of vector-borne diseases like Zika and chikungunya.12

Unfortunately, there are no observational studies to support such conclusions.

Modeling studies have been used to make the claim that climate change contributed to all of the above events. However, if we refer instead to actual observed outcome studies, we see that not only have droughts decreased, they have reached below-average historic levels.13 Global hurricane activity and intensity studies show no discernible trend in either frequency or intensity14 over the past 40 years,15 even when considering the popularly referenced Atlantic tropical storm activity.16 Finally, there has not been any discernible trend in global tropical cyclone landfalls since 1970,17 all in the face of a gently warming climate.

While incidences of vector-borne illnesses such as West Nile, Zika, and chikungunya are reported to be increasing in Texas, it very well may be due to increased testing and reporting practices, rapid globalization and population growth, transportation and migration patterns, and changes in vaccination rates. There is no conclusive evidence that these findings are due to climate change.18 Looking at mortality rates due to vector-borne disease may be more helpful in determining the burden of disease in a warming climate. A 2018 Journal of the American Medical Association article reveals that mortality rates from tick-borne spotted fever have decreased since 1980, while mosquito-borne West Nile Virus mortality incidence has fluctuated significantly in recent years. Therefore, there has been no clear trend since it’s discovery in 2000.19 Interestingly, the last peak death year for West Nile was 2012, a year that was considered to be a cooler “La Niña” season.20

While we are informed that heat increases the risk of wildfires, real world observations are contradicting that line of reasoning. The number of burned acres globally has declined in recent decades, despite a mildly warming climate.21 In fact, current fire models failed to predict the observed magnitude of fire declines to the point where the entire process of fire model projections have been questioned in regard to making valid projections.22 While it is true that western U.S. fire frequency and acreage burned have increased since 1980, those numbers pale in comparison to the period of 1920 to 1960.23 Blaming the Australian wildfires on global warming using untested, unvalidated modeling methods appears to be an anecdotal conjecture.

There are conflicting data regarding observed flooding globally. While it appears that flooding occurrence has risen,24 the magnitude of such floods has decreased.25 However, both death rates and number of people affected by floods have been in general decline.26

Both Dr. Haley and I agree that food crop yields have been increasing over time.27,28 This may very well be due to the increase of carbon dioxide in the atmosphere. However, Dr. Haley states, without supporting evidence, that protein and essential mineral content tend to create less nutritious foods. In light of decreasing global malnutrition highlighted above, this claim appears to be unfounded. Anecdotal stories about farms in Central America shutting down do not provide any evidence of a global food security crisis.

In regard to climate change increasing ocean temperatures, no real world observational trends have shown a direct link between degradation of the quality or quantity of shellfish and other seafood with CO2-caused ocean acidification.29 The only available studies linking oysters and other bivalve food vulnerabilities were completed in-vitro studies using impossibly low Ph levels of 7.2 and 7.4.30,31

My final evidence that climate change is not causing a crisis comes from a 2019 study on global vulnerability to climate and weather events. Global mortality and economic loss have plummeted by over 5 times since 1980.32 This is an enormously positive finding that directly challenges the premise of an impending climate crisis used to curb CO2 emissions.

What this data does show is that both humans and the earth are resiliently adapting to their environment in ways not experienced previously on human record. Most of this resilience is occurring in emerging countries such as in Africa, where the currently maligned carbon-based energy like oil and gas has been instrumental in creating vast improvement in infrastructure, commerce, technology, and human health outcomes.

In conclusion, we find through evidence-based observations, that global heat related illness and mortality rates have declined, especially in the elderly, that global malnutrition mortality have declined, especially in African children, that global food-borne illness and mortality incidence rates and malaria have declined, that U.S. tick-borne spotted fever disease mortality rates have declined, that global drought rates are declining to below historic averages, that global flood vulnerability events are declining, that global fire frequency and area burned are declining, that global frequency and intensity of hurricanes and tropical storms are largely unchanged, that U.S. food crop yields are increasing without evidence of nutritional loss, that West Nile mortality in the U.S. is not associated with record warm seasons, that global bivalve food sources such as oysters and clams have increased without real-world evidence for shell degradation, and that global vulnerability to natural disasters have decreased over 5 fold since 1980. All these findings have been made during a period of a gradually warming climate.

Dr. Haley acknowledges that the climate change field is controversial and that everyone may not agree with him. However, those who disagree are unable to debate even basic salient points of climate alarmism due to a climate debate “blackout” by the climate community. We are told that since “the science is clear and unequivocal”, and that “97% of climate scientists agree with this”, that no debate is needed. Given the evidence-based rebuttal provided above, I am curious if Dr. Haley or other climate alarmists would be interested in debating the points of  real-world, observational evidence presented above, and how it differs from model projections, and why physicians should educate patients about climate health effects using unvalidated models over observational evidence.

Scott Hastings, DO
Family physician, Frisco

1. Price, S. The Temperature’s Rising: Preparing for the health effects of climate change. Texas Medicine, May, 2020, p20-23.

2. Munthali, T., Jacobs, C., Sitali, L. et al. Mortality and morbidity patterns in under-five children with severe acute malnutrition (SAM) in Zambia: a five-year retrospective review of hospital-based records (2009–2013). Arch Public Health 73, 23 (2015) doi:10.1186/s13690-015-0072-1

3. Peng, W. et al. Global nutrition 1990-2015: A shrinking hungry, and expanding fat world. PLoS One. 2018 Mar 27;13(3):e0194821. doi: 10.1371/journal.pone.0194821. eCollection 201

4. WHO, World Malaria Report 2016.

5. MMWR Morb Mortal Wkly Rep. 2018 Mar 23; 67(11): 324–328. Published online 2018 Mar 23. doi: 10.15585/mmwr.mm6711a3 

6. Als, D. et al. Global Trends in Typhoidal Salmonellosis: A Systematic Review. The American Journal of Tropical Medicine and Hygiene, Volume 99, Issue 3_Suppl, 6 Sep 2018, p. 10 - 19

7. Mohammadsalehi, Holakouie Naieni K, Eshrati B, Mohammadbeigi A, Ahmadnezhad E, Arsangjang S. Trend of Cholera in the Last 50 Years and Modeling the Effect of Annual Temperature and Rainfall on Incidence of New Outbreaks in Iran (2005-2014). irje. 2018; 14 (1) :1-8

8. Wang, Y., Bobb, J.F., Papi, B. et al. Heat stroke admissions during heat waves in 1,916 US counties for the period from 1999 to 2010 and their effect modifiers. Environ Health 15, 83 (2016) doi:10.1186/s12940-016-0167-3

9. Lantos, T. et al, Seasonal variation of mortality from external causes in Hungary between 1995 and 2014. PLoS One. 2019 Jun 6;14(6):e0217979. doi: 10.1371/journal.pone.0217979. eCollection 2019.

10. Achebak, H. et al, Heat-related mortality trends under recent climate warming in Spain: A 36-year observational study. PLoS Med. 2018 Jul 24;15(7):e1002617. doi: 10.1371/journal.pmed.1002617. eCollection 2018 Jul.

11. Sheridan, SC. Et al, Temporal trends in human vulnerability to excessive heat. Environmental Research Letters, Volume 13, Number 4 19 March 2018

12. Price, S. The Temperature is Rising: Preparing for the health effects of climate change. Texas Medicine, May 2020, p 20-23.

13. Barichivich, J. et. al. State of the Climate 2018. Bulletin of the American Meteorologic Society, page S40, Sept. 2019.

14. Accessed 6/19/2020.

15.  Accessed 6/19/2020.


17. Accessed 6/21/20.

18. Hotez PJ (2018) The rise of neglected tropical diseases in the "new Texas". PLoS Negl Trop Dis 12(1): e0005581.

19. Hansen V, Oren E, Dennis LK, Brown HE. Infectious Disease Mortality Trends in the United States, 1980-2014. JAMA. 2016;316(20):2149–2151. doi:10.1001/jama.2016.12423.

20. Accessed 6/20/20.

21 Doerr Stefan H. and Santín Cristina. Global trends in wildfire and its impacts: perceptions versus realities in a changing world. 371Phil. Trans. R. Soc. B, 05 June 2016.

22 Andela, N. et. al. A human-driven decline in global burned area. Science 30 Jun 2017:Vol. 356, Issue 6345, pp. 1356-1362.


24. Hu, P. et. al, Flood-induced mortality across the globe: Spatiotemporal pattern and influencing factors. Sci Total Environ. 2018 Dec 1;643:171-182. doi: 10.1016/j.scitotenv.2018.06.197. Epub 2018 Jun 21.

25. Hong, X. do, et. al. A global-scale investigation of trends in annual maximum streamflow. Journal of Hydrology Volume 552, September 2017, Pages 28-43.

26. Jongman, B. et. al. Declining vulnerability to river floods and the global benefits of adaptation. PNAS May 5, 2015 112 (18) E2271-E2280; first published April 20, 2015.



29. Data from FAO FishStat 1970-2015

30. Bressan, M. et. al. Does seawater acidification affect survival, growth and shell integrity in bivalve juveniles? Marine Environmental Research. Volume 99, August 2014, Pages 136-14.


32. Formetta, G, et. al. Empirical evidence of declining global vulnerability to climate-related hazards. Global Environmental Change Volume 57, July 2019, 101920.


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September 02, 2020