Yeah, we tend to get a triple-whammy down south. I recall reading that the tilt of the earth, as well as atmospheric pollution make even more of a difference. If I recall the figures correctly, the UV hole can increase UV by ~3% in the southern hemisphere compared to the northern hemisphere, but the fact we tilt slightly closer to the sun in summer than the northern hemisphere makes 6-7% difference, and the fact that there is far less atmospheric pollution (aerosols, etc. that absorb some UV) in the south makes another ~6%. So even in summer when the UV hole is at its minimum, at the same distance from the equator you can have something like 12-14% more UV exposure than the northern hemisphere in summer.
It's ironic that better pollution controls, while causing many health benefits, will potentially make things worse for skin cancer in the northern hemisphere by gradually increase the UV doses, so you all are going to have to get better at sun safety or melanoma will become a much bigger issue there.
> but the fact we tilt slightly closer to the sun in summer than the northern hemisphere makes 6-7% difference
How could that be a fact? Axial precession (a) has a period that is much longer than a year, meaning there is no systematic difference between the northern and southern hemispheres; and (b) has a period that is MUCH longer than a year, meaning the difference between the northern and southern hemispheres in the same year is negligible.
I'm not following you. What is the difference between your point a and b? Did you just wrote "much" with capitals and reworded that there is no effect?
> Axial precession has a period that is much longer than a year
Yes, much longer. The cycle of axial precession is about 26,000 years.[1]
> meaning there is no systematic difference between the northern and southern hemispheres
This does not follow. The fact that the axial precession's period is much longer than a year means that the angle of the axis can be considered approximately constant during a year. Why would that mean there is no systemic difference between the northern and southern hemispheres?
"Axial precession makes seasonal contrasts more extreme in one hemisphere and less extreme in the other. Currently perihelion occurs during winter in the Northern Hemisphere and in summer in the Southern Hemisphere. This makes Southern Hemisphere summers hotter and moderates Northern Hemisphere seasonal variations."
> The fact that the axial precession's period is much longer than a year means that the angle of the axis can be considered approximately constant during a year. Why would that mean there is no systemic difference between the northern and southern hemispheres?
Well, you're citing the conclusion of point B and then responding to the conclusion of point A. (Yes, they have identical premises, but B is more technically accurate.)
If the obliquity[1] of the earth is constant during a year (which it effectively is), then there is no difference in the obliquity of the earth between summer of year X and winter of year X, and therefore the obliquity of the earth cannot be responsible for any difference between the northern hemisphere and the southern hemisphere. This should be painfully obvious.
Back on point A, in order for there to be a systematic difference between the seasons in the northern and southern hemispheres, precession would need to have a period that was a multiple of the solar year. This would keep the difference in place over time. Without meeting that requirement, the hypothetical precession-based phenomenon would wander through the calendar year, which would prevent it from systematically having different effects in different hemispheres.
Being a multiple of the solar year is not ruled out by the fact that the precessional period is on the order of tens of thousands years, but it becomes vanishingly unlikely.
> Did you just wrote "much" with capitals and reworded that there is no effect?
No.
> What is the difference between your point a and b?
They are addressing different points.
One is talking about year-to-year differences; if summer in December 2437 is hotter than summer in June 2437, does it follow that summer in December 12437 will be hotter than summer in June 12437? (No, because the precessional period is not related to the orbital period.)
The other is talking about within-year differences. If summer in June 2437 is whatever temperature it is, does it follow that summer in December 2437 will be hotter than that? (No, because the precessional period is much longer than the orbital period.)
> Axial precession makes seasonal contrasts more extreme in one hemisphere and less extreme in the other. Currently perihelion occurs during winter in the Northern Hemisphere and in summer in the Southern Hemisphere. This makes Southern Hemisphere summers hotter and moderates Northern Hemisphere seasonal variations.
This is logically incoherent. There are two problems:
1. Axial precession isn't doing any work here. The difference, as described, comes from an interaction between the earth's orientation and the eccentricity of its orbit. Axial precession has no role to play in the phenomenon; the conclusion ("southern summers are hotter and southern summers are colder") would be equally true if there was no precession. (In fact, more true, since in that case it would remain true into the future.) The effect of precession is described in the following sentence:
> But in about 13,000 years, axial precession will cause these conditions to flip, with the Northern Hemisphere seeing more extremes in solar radiation and the Southern Hemisphere experiencing more moderate seasonal variations.
2. Perihelion is not a concept related to the obliquity of the earth or the axial precession. As such, once you've invoked perihelion, you can't attribute responsibility to obliquity or precession. Going by the description here, there is a period (perihelion) which causes the seasons in one part of the earth to be more extreme, and axial precession is the phenomenon that causes which part of the earth experiences that greater extremity of climate to shift over time. How do you get from "axial precession distributes the effect of perihelion evenly over the earth" to "axial precession is why the seasons are more extreme in the southern hemisphere"?
So, going back to the original claim:
>> but the fact we tilt slightly closer to the sun in summer than the northern hemisphere makes 6-7% difference
This is not a fact. It's false. There is no significant difference in tilt. The difference is in physical distance to the sun, not angular distance to the sun.
---
[1] You're making a mistake here; the angle of the earth to the orbital plane ("which latitude points directly at the sun?") is not affected by axial precession ("where in the sky is the north pole?"). I was making the same mistake.
Atmospheric pollution scatters and absorbs some UV light in the upper atmosphere and stops it reaching the ground. While reducing pollution is a net good, one unfortunate consequence of controlling and reducing the pollution that gets up to the upper atmosphere is that it will lead to a few percent increase in the UV dose people receive in the northern hemisphere. Skin cancer is associated with UV exposure so incidence of skin cancers will go up if sun safety is not observed.
Oh it's far more than that. Giant volcanic eruptions have been responsible for non negligible reductions in global temperatures due to reducing the sunlight which hits earth via scattering and other effects due to the pollution.
They probably didn't mean to a large degree, but air pollution does scatter light and UV radiation. As well as cause breathing problems, asthma, probably lung cancer, etc.
The sun has been really strong since the early 2000s. It's a shame that the Southern hemisphere got that affected given it probably produced less than 20% of the damage.
It always gives me some faith again to hear the ozone layer is recovering. I feel that if this crisis had began in our current times I would resign myself to believing the ozone layer would completely disappear at some point and we’d be cooked.
I am confused by the transition in this story. Did the same assessment simultaneously measure both the decreasing "Chinese rogue production" and potential effects of geoengineering?
I live in the southern hemisphere, and I've travelled a bit. The sunlight where I live is of a hard, stark, dazzling kind. A brilliant white that reflects off surfaces with increased intensity. It reminds me of the photos of spacewalking astronauts doing repairs, their suits ablaze and every surface overexposed.
I find sunglasses a must-have in these conditions.
Sitting in the sunlight on an even mildly sunny day is scary. If you're paying attention, after only five minutes you'll notice a burning sensation on your exposed limbs. And that is actually what is happening - you're being fried by the Sun's rays.
This sounds funny but I actually really dislike the light in Australia in summer. It's really white, washed out and sterile, it sounds weird but it kind of makes me feel a bit depressed. Similar to how I hate the light from fluorescent bulbs.
I'm not sure if this has to do with just the angle of the sun or the hole in the ozone layer? But it's definitely something I've not really felt in many other places, or I've ever seen in the Northern Hemisphere.
Early morning and afternoon on a Sydney beach is beautiful, Midday ? No thanks.
i know what you mean. australia has an UV index in summer between 10 and 14. sun protection is usually recommended between 9am and 6pm. thus skin cancer is australia’s most common cancer.
They are lying. They are not even close. "Antarctic ozone hole is 13th largest on record and expected to persist into November " 2021. They have declared it solved every two years since it was discovered.
My one-step-shy-of-tinfoil-hat dad loves to say that he thinks climate change is BS. He has no expertise on which to claim this, but when prompted he'll cite "it used to be that we had to worry about the ozone layer ... " -- I'll patiently explain how the Montreal Protocol has mitigated the problem, that's why it doesn't come up anymore. And bringing up the ozone layer is actually a great case for policies that intervene to preserve our environment.
He'll generally change the subject or focus on some other modern "dystopia" rather than acknowledge being wrong.
Bring up the fact that it's going to take decades for the ozone layer to reach its previous levels.
We still have to worry about the ozone layer, it leads to higher rates of skin and eye disease, including cancers, it can have deleterious effects on plants, phytoplankton and fish, and it can accelerate the breakdown of different materials[1].
Increased radiation reaching the surface of the Earth has a ton of effects on humans that are pretty awful[2].
When the ozone layer was being depleted, did the scientists sounding the alarm say that it could be healed in this period of time? Honest question. If not then your father might be reacting to doomsaying that turned out to be overzealous.
At the time there wasn't much focus on timelines (besides being a long term undertaking), only that there was a hole in the ozone layer and that it could be fixed by avoiding certain refrigerants. As they were taken off the market the progress in regulating the CFCs and the ozone layer healing was noted, and it faded away as a concern.
At the time I lived under said hole, so it was in the news quite a bit.
For some people, debating is personal, an attack on the person itself rather than the argument. So losing the argument is kind of akin to losing face yourself. People become emotional in such a setting. It’s a sign of over investing in a belief system with (ad hoc) rationales attached to it.
This is really low quality thread material and brings nothing to the conversation.
Cant you bring this kind of pointless addedums to that other site that must not be named?
Many people have relatives like that and one of the key challenges for this century is figuring out how to get them to understand that the fossil fuel industry propaganda they’ve been steeping in is wrong. A successful example of collective action solving a problem at minimal cost to the economy seems like an important tool in that effort.
Yeah ... he had it! In his glory days he would talk proudly about Jonas Salk but after decades of watching the Two Minutes Hate he may not be such a big fan anymore.
Might be safer to just let this slide, not talk about ozone/climate and try to gently steer him away from antivax, qanon stuff etc. Can be nigh on impossible to bring anyone back from that
> Looking at stratospheric aerosol injection, “is in our wheelhouse,” he added.
> There is a lot of uncertainty in their findings, Dr. Fahey said, but the basic message is that trying to cool the planet by 0.5 degree Celsius (0.9 degree Fahrenheit), say, through the use of sulfur aerosols, would have some effect on ozone.
Why are these people qualified to mess with our climate?
Because they have dedicated their lives to understanding the physical world and do understand it far better than most. “Dr. David W. Fahey is the Director of the Chemical Sciences Laboratory in the National Oceanic and Atmospheric Administration in Boulder, Colorado, USA. He joined the Laboratory after receiving advanced degrees in physics.”
Utterly irrelevant. That they or anyone should have any more of a say at planetary geo engineering over the one habitable planet our species reside on. Unless you believe in some sort of intellectual tyranny. What if the “smart” credentialed people were ones you didn’t agree with and proposed eugenics as a viable solution to over coming climate change would you be so quick then. I doubt it. Not trying to call you out here but this line of reasoning that they are an expert so get to do this is bonkers. Sure propose all you like but my lord no action.
This is actually already happening somewhat, due to the use of high-sulfur fuel oil by container ships. Of course, the irony is that certain organisations are attempting to lower this sulfur content, without the realisation that it's actually helping to moderate the temperature of the planet.
Sulfur dioxide in the troposphere isn’t very long lived and won’t make it to the stratosphere where it actually has a surface cooling effect. Even small volcanos have very little impact on stratospheric aerosol formation since they do not inject sulfur to high enough altitudes. Only very powerful surface injections have long lasting stratospheric effects.
Organisations aiming to reduce sulpfur in ship fuel are defiitly aware of the cooling impact it has on the climate. However, the health benefits of this reduction are not to be understated - with shipping sulfur being responsible for 100s of thousands of premature deaths and millions of cases of childhood astham annually [1].
The cooling effect from ship pollution is there, but it is a relatively small fraction of the ovrall cooling from atmospheric aerosols.
Depends on who you are and thus what is important. Farmers generally consider no acid rain good, even though they now have to buy sulfur fertilizer for their fields, where acid rain added plenty before for free.
they are more qualified than the capitalists that did this. look up thomas midgley jr and see what an absolute shitshow of a environmental disaster his entire career was. he ended up dying to one of his inventions at the end too.
https://ozonewatch.gsfc.nasa.gov/
Those of us in the lower southern hemisphere get hit pretty hard with UV radiation in spring (Sep-Nov).