Guest Essay by Kip Hansen
The venerable NY Times carries this headline: “In India, Slight Rise in Temperatures Is Tied to Heat Wave Deaths”.
The study cited makes this conclusion:
“Mean temperatures across India have risen by more than 0.5°C over this period, with statistically significant increases in heat waves. Using a novel probabilistic model, we further show that the increase in summer mean temperatures in India over this period corresponds to a 146% increase in the probability of heat-related mortality events of more than 100 people.”
Heat waves can be killers. More Heatwaves = More Deaths. Longer Heatwaves = More Deaths. Heat waves are prolonged periods of excessively hot weather, which may be accompanied by high humidity, especially in oceanic climate countries. Heat waves tend to carry off the old, infirm, and vulnerable young ….(there is more, but you have to wait for it).
The rest of the study, the story and the claims are the result of questionable statistics, which even the study authors admit (or brag) are “novel”.
The whole case can be made using nothing but the study’s figures:
The authors insist “Figure 1A shows that summer mean temperatures have increased substantially from 1960 to 2009. The time series exhibits a statistically significant (95% confidence interval) upward trend confirmed using the Mann-Kendall (MK) trend test. The accumulated intensity, count, duration, and days of Indian heat waves have also increased over the analyzed time period over most of the country and especially in the northern, southern, and western parts of India (Fig. 1, B to E).”
Temperatures increased substantially if we look at a National Average (mean) — the actual increase in the National Mean Summer Temperature trend is from 27.55 to 27.9, an increase of 0.35 °C ) or 0.63 °F. (Note: not the claimed 0.5 °C, which is a rounded up exaggeration) In the fifty (50) years of the data set, this gives an increase of 0.07°C/decade. This increase we will simply have to accept as valid, though we must point out that the National Average Summertime Surface Air Temperature may not be the best metric to use to judge what are obviously very localized heat wave events, according to the sub-panels B thru E, and may be skewed by UHI effects in India’s massively huge urban centers. India is huge and geographically diverse — from the tropical southern provinces to high Himalayan plateaus — making a “national” average temperature meaningless in this context.
The rest of the story is contained in these two excerpts from Figures 2, 3 and 4:
The primary feature of these two graphs is that they are long-term flat, with a couple of spikes and dips.
Look back up at the National Average Temperature graph — it shows a particularly low national temperature in 1971, which shows up the these two graphs as extremely low population-weighted and income weighted heat wave deaths. And we see the existence of two (possibly three) unusually high years, 1997 and 2003.
Here’s where the “novel” statistics takes place:
Panel C shows what we expect — The more heat wave days, the higher the average temperature.
Panel B likewise is as we would expect — longer heat waves are more likely to produce more deaths.
Panel A however, compares a probability density of Mean Summer temperature of 27°C and 27.5°C .
Look at the original temperature graph one more time, where do 27°C and 27.5°C appear:
The apparent novel statistics involves comparing the data of a low temperature year, like 1971, (very near 27°C) — not with the most recent period, not the most recent decade, not the high temp end of the graph — with 27.5°C which appears at the beginning of the time series, in 1960 and looks like the approximate average low limit for the data set.
I am, admittedly, confused by this selection of temperatures for the probability densities in Fig 4A — but it appears to have been chosen to “prove” the hypothesis of the effect of a 0.5°C rise in temperatures. Where could they have gotten death data for 27°C ? Not even a single year in the 50 year time series has national average temperatures that low. Neither the full published journal paper nor the Supplementary Materials contain any explanation for the choice of temperatures in the Figure 4 probability distributions, however the SM have results different (by several percentage points) from those in the published paper [see fig. S6. Results of a conditional probability density analysis of mortality given certain thresholds for summer maximum temperatures].
The two Deaths graphs above reveal the more scientifically correct findings of the study, which do come to light in the whole journal article, but are not highlighted in the Abstract, the Press Release, or the MSM. Quoting from the paper:
“In an effort to understand the underlying mechanisms of heat wave mortality, we further explored its relationship with population and income levels in India. Figure 3 shows that the relationship between population-weighted heat wave days and mortality rates is only slightly better than that between mortality and summer mean temperatures …; however, the correlation between income-weighted heat wave days and mortality rates is better….”
“These observations reinforce previous work that highlighted poverty as a significant factor in climate-induced mortality, such as heat wave deaths..”
The Bottom Line:
The nugget of truth: Heat waves can be killers. Heat waves tend to carry off the poor, especially the poor elderly, the poor infirm, the poor vulnerable young.
But, primarily, it is Poverty that kills. It kills the old, it kills the infirm, it kills the very young, it kills the weak.
Any stressor, be it heat waves, cold snaps, drought, political instability, inflation, armed conflict or price increases of basic food staples will cause spikes in deaths, especially among the poor — and the poor in India are very, very poor.
We really didn’t need another study to tell us that — and the use of “novel statistical methods” [stretching the truth] in an attempt to claim that “moderate increases in mean temperatures may cause great increases in heat-related mortality” does not contribute to the sum of human knowledge.
If we want to save lives, to decrease the threat of changing climatic conditions, we need to fight poverty — at the household level where real people live.
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Author’s Comment Policy:
I’d be glad to answer your questions and respond to your comments.
I am not an expert in climate science — so I don’t respond to Climate Warrior salvos from either side of the great divide.
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