Comment by Markoff | Hacker News Reader

Comment by Markoff | Hacker News Reader

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"While heatwaves are common in India, especially in May and June, summer began early this year with high temperatures from March, when the first heatwave arrived."

for anyone who thinks 49C in Delhi is some extreme temperature it's not really that far from usual maximum (2019 and 2020 both May max. 46C), I remember when I traveled during similar period all across India in non-AC bus (must been easily 50-60C inside) and when there was a bit of rain and temperature dropped to like 36C it felt so cool and refreshing, somewhere outside Delhi had to literally run to shadow in early afternoon with 40+ C temperatures

"The temperature was recorded at 49.2°C in northwest Delhi’s Mungeshpur and 49.1°C in southwest Delhi’s Najafgarh. It was the first time any weather station in the national capital breached the 49°C mark. These two automatic weather stations became operational only this year, so no past data is available, but the previous high in Delhi was recorded at 48.4°C at the Palam station on May 26, 1998."[1]

so not really a fair comparison, they should show current data from Palam station to see whether this is record ot not

edit: Palam station highest temperature in last 24 hours 46.4C, so not beating Delhi record, typical BBC "quality" reporting[2]

[1] https://www.hindustantimes.com/india-news/temperature-tops-4...

[2] https://city.imd.gov.in/citywx/city_weather.php?id=42181

  for anyone who thinks 49C in Delhi is some extreme temperature it's not really that far from usual maximum (2019 and 2020 both May max. 46C).

That's a 3C increase!

Sure that's only a 6.5% increase in temperature w.r.t. to 46C but that's an incorrect way of looking at it. If you were to set your air-conditioning to 32C, then the energy required to cool from 49C to 32C is 21% more than the energy required to cool from 46C to 32C.

32C is also the wet-bulb temperature, so when thinking about tolerability, at least use 32C as the baseline (and not 0C) when comparing temperatures.

P.S. Humidity is a major factor. I'm assuming humidity is the same this year as it was the previous years.

Edit: To clarify, my comment was about not giving into your insticts and underestimating the effects of 3C rise w.r.t. 46C. Thinking of 3C rise in terms of energy increase or comparing it to a baseline of wet-bulb temperature give you better intuitions.

Pretty sure that's well within the bounds of normal variation we'd expect between different locations within a major city. There's all kinds of weird microclimates in most cities, you really do have to compare like with like here - it's entirely likely that there were actually higher temperatures in Delhi in the past and there just weren't automated weather stations in those locations at the time.

Except the 49C here is not a weird microclimate of some small part of New Delhi, but rather is the average temp across the city.

Which means that places with weird microclimates that were 49C when the overall temp was 46C are now 52C and above.

except the real temperature was around 46C and only two new weird stations reported 49C, I wonder how is their accuracy even regardless microclimates

Which stations reported 52C? I’d think that would be the headline of true.

> it's entirely likely that there were actually higher temperatures in Delhi in the past and there just weren't automated weather stations in those locations at the time

Ok, great, so maybe at some point in the past there was a hotter temp. It’s amazing how rather than focusing on the miserable experience nearly 50° weather is for those there, we get into a weird measuring fetish over who’s number is biggest.

> That's a 3C increase!

Not if you don't compare apples and oranges, these high temperature data come ONLY from 2 NEW automated stations with no previous data to compare, other stations used for years didn't report such crazy temperaturs, so you should take these new data with grain of salt. You should be comparing stations in same location with comparable data from previous years.

I agree with the important sentiment in your comment, i.e. that a 3 °C increase is a lot… but:

> Sure that's only a 6.5% increase in temperature w.r.t. to 46C

That's not how this works at all. The Celsius (and Fahrenheit) scale sets an arbitrary zero point. To compute the increase in temperature, you need to use an absolute scale, such as Kelvin: 49 °C is 322 K, and 46 °C is 319 K. The increase from 319 K is about 1%.

Think about it this way: Distances are typically measured in absolute units – m, km, feet, miles, whatever. Suppose I introduce a new unit with an arbitrary zero-point, say "1 Blarf is 2 m, but 0 Blarfs is defined as 5 m". That means that 3 m is -1 Blarf, 7 m is 1 Blarf, etc. That still doesn't mean that 2 Blarfs (9 m) is twice as long as 1 Blarf (7 m), even though it would seem that way from naively considering the numeric values of the two lengths in Blarfs.

TLDR: Arbitrary zero points are stupid.

You haven't corrected the posters mistake, you've repeated it.

Intervals can only be converted into percentages across another interval, you've decided that the whole interval is the interesting part but it isn't, 0K is as abitrary as 0C for this purpose. Is a day 1/7th of a week or 1/365th of a year? Yes. It's also some tiny fraction of all time since the Big Bang, but who cares about that? That's your absolute interval.

There isn't a proper way to do it and it's nearly always a mistake to try.

I disagree.

Their way of doing the conversion is far more principled than the original commenter's.

It's absolutely appropriate to do a percentage conversion based in Kelvin, the percentage has a fundamental meaning in terms of the actual increase in kinetic energy. You would get the same percentage if you did the calculation in Rankine because they're both 0-based temperature scales.

No, 0 K isn't arbitrary. That's exactly the point; it's the lowest temperature for which the definition of temperature makes sense.

Your analogy about days relating to weeks or years is wrong. This is a matter of scaling. In this sense, Kelvin is of course arbitrary, but said scaling does not matter for the computations in question.

If the poster had written "49 C is 6% further than 46 C from the point at which water freezes", then we'd be in agreement that their choice of interval is no worse or better than others. But absent such a clear labelling, the only notion that makes sense is the absolute one.

No. You are comprehensively wrong about the relationship between intervals and other intervals with regard to percentages, and you have refused to learn from what I just said.

> Kelvin is of course arbitrary

Listen to yourself if you won't listen to me.

Edit: read up on the difference between temperature and heat. I suspect that your mental model of that relationship is wrong, and that's why you're making this mistake.

> > Kelvin is of course arbitrary

> Listen to yourself if you won't listen to me.

Like I said: Kelvin is arbitrarily scaled. Scaling doesn't matter when it comes to ratios. Celsius on the other hand is also arbitrarily offset. That matters.

> Edit: read up on the difference between temperature and heat. I suspect that your mental model of that relationship is wrong, and that's why you're making this mistake.

I'm quite aware, thank you very much. This whole subthread is about temperature. To be clear: I'm not criticising OP's writings about energy requirements. I'm merely talking about:

> Sure that's only a 6.5% increase in temperature w.r.t. to 46C

Yes, that is indeed followed by

> but that's an incorrect way of looking at it.

but that refers to a discussion of energy that follows. My whole point is that it's *NOT a 6.5% increase in temperature". OP's point seems to be that we shouldn't be considering the increase in temperature, but rather the increase in energy needed. That's fine. No objections. I'm just saying that the statement about the increase in temperature is also wrong.

> Kelvin is arbitrarily scaled.

Percentages are unitless, you're making a trivial observation that didn't need to be said.

I conclude that you lack the appropriate education to discuss this subject.

> Percentages are unitless, you're making a trivial observation that didn't need to be said.

My original observation was that Celsius and Fahrenheit are arbitrarily shifted, and that matters. Then you countered that Kelvin is arbitrary too, to which I write that it is only arbitrarily scaled, and that is fine (of course, for the exact trivial reason that you point out).

If your best argument is that I made a correct but trivial statement in addition to my main point, then I don't think there's much more to be had from this discussion.

I bid you farewell.

For some reason you seem to have ignored the second half of the sentence I wrote.

> Sure that's only a 6.5% increase in temperature w.r.t. to 46C ... but that's an incorrect way of looking at it.

I've added an edit to clarify what I was aiming at.

> For some reason you seem to have ignored the second half of the sentence I wrote.

I can't see that the second half rectifies it though. The rest, the part about the energy needed being what mattered, I wholeheartedly agree with. It's still incorrect to say that the temperature is 6% higher.

Sure, I agree that it's incorrect. I should have used 0K as base.

49C is hot, even if India has seen hotter temperatures. Heat must also be seen in combination with humidity, i.e. Wet Bulb Temperature[0]. Note that the human limit for WBT is extremely low when compared to dry heat (Wikipedia gives the theoretical limit as 35°C/95°F, equivalent to a heat index of 70°C/160°F) because this is the point where the human body is incapable of self-regulating body temperature because perspiration ceases to have any effect. If it really was 60°C inside, something like 15% relative humidity could have been enough to kill you without ventilation/isolation/cooling if you had been exposed to it long enough.

The other problem that you seem to be missing is that the article states that this heatwave arrived very early, which means nobody was prepared for it and as the article also states, this could cause problems in agriculture which would compound on the existing shortages from Ukraine. This is as usual unlikely to cause direct problems for people living in most of Europe or North America but bad news for countries relying on Ukraine or India for food imports.

[0]: https://en.wikipedia.org/wiki/Wet-bulb_temperature

Good thing we have about 4 years of reserves in godowns across India, and have banned exports then :)

Good thing we used the IMF to make starving African countries self-sustaining and food secure instead of pressuring them to mass produce non-food crops for the international market then. Oh, wait.

It's a big difference if it's already 45+ in March when it's usually only 45+ starting in May.

I don't know, definitely feels hotter this summer compared to the last two.

I'm not sure how true this is but I noticed that 1.1°C of warming has raised maximum temperatures by 4°C in Germany. Yes those 4°C aren't there all year but you do notice them.

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