3
$\begingroup$

I grew up in a small town on a sea shore with hot and sunny summers (up to 30-35° C). I remember myself, my friends and relatives being outdoors for 12 hours a day. We never needed sunscreen, and never used it. It was considered, that skin can burn on the first day of taking a sunbath and precautions were taken, i.e. "put a long-sleeved shirt on after three hours in direct sunlight". Coordinates of my hometown are 46°45′35″N 36°47′04″E.

Currently, I live in another town, very close to an ocean shore, with coordinates 41°4′9″N 73°51′35″W, and we have hot and sunny summers (up to 30-35° C, sometimes a little bit more). I am very surprised how aggressive sun is here. We need sunscreen all summer long, and once I had to work outdoors for 8 hours at the beginning of September, and I somehow got a sunburn.

Given my childhood experience, it would be impossible for me to imagine, that I could get a sunburn at the end of summer. I simply used to get a very nice suntan over summer, and then my skin was resistant to sunburn. I wonder what is an explanation for this. One explanation could be that sun is more aggressive in my current town, than it was in my home town. But why? Another explanation, that there are some other factors involved, but I am not sure what these factors could be.

If anyone knows what is an explanation for this phenomenon, I would be most grateful for your help.

$\endgroup$
  • 1
    $\begingroup$ Well, it could be that you're older, and don't spend the same sort of time outside as you did when you were a kid. You might be spending the middle of the day working indoors, and only getting out in mornings & evenings when the sunlight has to pass through more atmosphere to get to you. $\endgroup$ – jamesqf Apr 17 '17 at 5:43
  • 1
    $\begingroup$ @jamesqf: These are all good factors to consider. However, it does not explain, why during my childhood summers we were OK without sunscreen, and now we need it (almost) every day of summer. $\endgroup$ – Sleepy Hollow Apr 17 '17 at 11:54
  • 2
    $\begingroup$ Something to consider is the difference in ozone levels. In your youth, there may have been more ozone in your former home in the Ukraine, whereas now (I gather, some decades later) there may be relatively less ozone in your current location in New York. $\endgroup$ – Fred Apr 17 '17 at 12:16
  • 1
    $\begingroup$ @Fred, so you think, that reason might be a thickness of ozone layer. As I have relatives of the same age in both my home town and in my current town, we can exclude age difference and also the fact that I speak about relatively remote past from our equation. Is there any reliable source where I can check ozone level at this two locations over let's say past 10 years? Thank you! $\endgroup$ – Sleepy Hollow Apr 17 '17 at 17:20
  • 1
    $\begingroup$ @Sleepy Hollow: The question I'd ask is whether kids today actually need sunscreen any more or less than they did when you were a kid, or whether medical research and marketing have convinced parents that putting sunscreen on their kids is a good thing. You could say similar things about for instance child car seats: they were unknown in my childhood, but now I believe they're required by law. $\endgroup$ – jamesqf Apr 17 '17 at 18:24
4
$\begingroup$

I believe this is biology related, not weather related

I think your story is a bit anecdotal because there is no measurable evidence that the sunlight energy deposited into your skin is actually stronger in New York as compared to Ukraine. Let me offer two lines of evidence that this change is more likely to be related to you and your skin than it is to the weather.

First, Rostov-on-Don, (the nearest large city I could find sunlight data for) has sunnier summers than New York. From NOAA via Wikipedia, Rostov has 286/314/293 hours of sunlight in June/July/August. New York has 257/268/268. This is largely because New York sees two more rainy days per month (and about twice as much rain on those rainy days) during the summer.

Sunlight intensity at a certain latitude is directly related to the angle of incidence of the sun. The declination of the sun is the relative angle from the sun to the horizon given your latitude and the time of year. The sun moves (well the Earth moves...) from the Tropic of Cancer to the Tropic of Capricorn each year, from 23.45 N to 23.45 S. During the northern hemisphere summer solstice, the sun is directly above the Tropic of Cancer. From New York, the angle of incidence of the sun is thus 41.07 N - 23.45 N = 17.62 degrees. During an equinox, when the sun is directly over the equator, the angle of incidence of the sun is 41.07 N - 0 = 41.07 degrees. The cosine of the angle of incidence is the percentage of full equatorial sunlight energy that you would receive at that latitude. Thus, in mid-summer in NY, you get cos(17.62) = 0.953 of maximum possible sunlight; at the equinox you get cos(41.07) = 0.754; at the winter solstice you get cos(64.52) = 0.430.

For any point in the Northern Hemisphere outside of the tropics, sunlight intensity will always be greater at all times of the year at lower latitude. Thus, New York always has greater sunlight intensity than Ukraine...but the difference is not very significant. At summer solstice NY gets 0.953 of the max sunlight, but Ukraine gets cos(23.3) = 0.918 of max sunlight. This is the difference between early July and mid-August in NY; not very significant. Given the close latitudes involved, you would expect to have gotten more net sun in the summer as a child than you do now due to fewer cloudy days. Since this is not what you observe, there must be some other explanation.

Secondly, I grew up near Boston, and my mom made me wear sunscreen in the summer. I used to get sunburns pretty bad. Now I'm 35 and I live in Virginia and I never wear sunscreen, even when I get to the beach. I don't remember the last time that I got a sunburn. Things change, I guess? This is a purely anecdotal observation, but then so is yours. Without any data to measure the changes (maybe I am smarter about being in shade in my older age?) all I can offer is guesses.

I think you should be looking at either your skin or your behavior as the cause of this change, not necessarily at the climate.

$\endgroup$
  • $\begingroup$ I asked this question in Earth Science.SE for reason, as I am interested if there any data about activity of sun in different regions. Thank you for your advice, I will look into non-climate factors as well. But I am still interested in climate factors. Total number of hours of sunlight might be important, but it could be that quality of sunlight is even more important. * Also "Given the latitudes involved, you would expect to have gotten more sun in the summer as a child than you do now." - how exactly amount of sunlight correlates with latitude? Thank you! $\endgroup$ – Sleepy Hollow Apr 17 '17 at 21:56
  • 1
    $\begingroup$ "More sunlight is received at latitudes nearer the equator than near the poles where the midday angle of incidence of radiation is greater." - found a source on that. ecoca.ro/meteo/tutorial/Climate/Older/Latitude.html However, again, my question is not about number of hours, but about quality of sunlight. I guess, I have to start googling "ozone thickness in different geographic areas". $\endgroup$ – Sleepy Hollow Apr 17 '17 at 22:08
  • 1
    $\begingroup$ @SleepyHollow I beefed up the explanation of how sunlight intensity relates to latitude. $\endgroup$ – kingledion Apr 18 '17 at 12:08
  • 1
    $\begingroup$ Another consideration is reflected solar radiation. It is possible that you get a greater exposure in your present location due to the presence of buildings and concrete surfaces. A similar example is that boaters often find they need greater sun protection due to reflection off the water that can burn skin even where shaded by a hat. $\endgroup$ – haresfur Apr 19 '17 at 22:36

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.