Back in the sixties, there was a documentary made about a couple of surfer dudes who traveled around the world and between northern and southern hemispheres in search of constant summer weather and waves.
But that’s not what I’m talking about.
I’m talking about a foolish god, the God of Surfer Dudes, who decides to make an Endless Summer in the Northern hemisphere (or Southern, I don’t care which). This god–we’ll call him Brodhi–knows that seasons are determined by the Earth’s axial tilt toward the sun. So Brodhi affixes the Earth’s axial tilt so that, from now on, it’s aligned toward the sun exactly as it is on June 21, the summer solstice for the Northern hemisphere. Up here we get endless summer; the Southern hemisphere gets endless winter.
What would happen?
I’m almost positive it means the end of humanity, and possibly the end of all multicellular life. But how quickly? And what does the process look like?
Maybe I should write in to Randall Munroe; but if any of you have insight, I’d love to hear it.
Looking at temperatures, Global South winters are far more mild than Northern ones. South Africa has what Canada would consider to be a nice spring day, and Australia starts at “Springtime in Canada” and ranges upwards to “Summer in Canada”.
Antarctica would be in perpetual darkness, so its ice pack would increase, but would it be enough to make the rest of the Southern Hemisphere become a new ice age?
The Global south has a lot less land, and a lot more ocean, and the oceans would be far more efficient at moving heat around, so the temperature would be more stable.
Europe and Asia will become hotter overall, and the areas which are currently deserts would likely expand. But at the same time, you’d get more water evaporating, and thus being available for rain, so the rainier areas would get more rain. So there’d probably be a more extreme mix of wet rainy areas and deserts, with not as much in between.
I don’t think it would be an extinction level event, though. Life has persisted during both ice ages and periods of greater average temperature, after all. But human civilization would probably undergo a serious collapse over a few decades.
Now, if you were to flip it, and make Australia Permanent Summer, I think you’d be more likely to get an ice age covering Europe and a lot of Asia, but that still wouldn’t kill everything.
What is the effect of growing deciduous trees in the tropics? Do they still shed their leaves annually, or would they be perpetually green? (IIRC the trigger for dropping leaves is the declining daylight time). SImilarly, what triggers flowering and fruiting? Would we have cherries all year long or no cherries at all because the trees never flower? How about annuals - wheat, vegetables? do they grow and fruit any time, or do they need the change in daylight cycles? Plus, without frost risk, things like palm trees and citrus fruits could be grown fairly far north.
The other question is what it does to ocean circulation and weather cycles. Some effects ( el niño comes to mind) are driven by seasonal changes. IIRC this also triggers seasonal behaviour like salmon runs for spawning. Suffice to say the effects on biology/ecology would range from the subtle to the profound. Would our birds be confused?
While some aspects of how the Earth’s climate works are factual, I think that overall this topic requires too much speculation and opinion for FQ. Moving to IMHO.
I think this would be a lot more severe than an ice age. Think of how much hotter August is than June: it’s because we’ve had sustained months of increased sunlight. What would happen if that increased sunlight were sustained not for weeks at a time, but for years at a time? If June is hotter than August, how much hotter would October be, and then December, and then all the way to next June, with a year’s worth of increased sunlight? Conversely, the Southern hemisphere might get much, much colder with the decreased sunlight; I think it might be much more severe than ice ages.
This, and the effects on currents and plant and animal life, are excellent points.
All of this comes down to how much the circulation of the atmosphere and oceans change. Weather cycles will become more extreme, but will they find a new equilibrium that sustains life?
Weather cycles will be very weird. Yes, we’ll develop hotter spots and colder spots than we currently have, but those spots will also become much more stable. Without seasonal variations, we’ll end up with a more fixed weather system, even as the temperature and pressure differences that drive storm activity become more extreme.
Just to clarify, and if I understand correctly, in order to fix the axial tilt to be always towards the sun in a certain area, wouldn’t the axis of the earth have to be moving back and forth as the earth orbits the sun? I wonder what that would do the moon, among other things? I guess we’re assuming we can get to that result without gigantic tectonic disaster, like in the movie 2012.
Anyway, without seasons, I would expect widespread fires in the perpetual summer area (since I live in California I’m a little sensitive to that) and no rain to put them out. Presumably the non-summer hemisphere would be perpetual winter, and much of the world’s free water would be trapped as ice, in much larger areas than we now have. So drought and dropping ocean levels would result.
The Earth already wobbles, but it’s a very slow wobble (it takes something like 25,000 years for it to wobble around once). You would have to increase that wobble to once every 365 days, though syncing it to the Earth’s orbit would require Surfer God magic, otherwise it’s going to slowly go out of sync.
There are some interesting things at play here, most of which I don’t know enough about how our climate works to comment on. First, while we tend to think of the Earth’s land as being roughly evenly distributed between the northern and southern hemisphere, it’s not. There is significantly more land above the equator than below it.
The second thing is that there are two vastly different scenarios possible. Warm and dry would probably lead to an extinction level event of sorts. At least once in Earth’s history the area around the equator become uninhabitably hot. Plants and animals died in massive numbers. But the areas further away from the equator became habitable, and you had forests up around the north pole that were rich with life. On the other hand, warm and wet would make the northern hemisphere into a lush rainforest, with its habitable land extending far up into Canada and northern Asia.
Whether we’ll end up with warm and wet or warm and dry is something that is well beyond my abilities to speculate on. My gut instinct is that the northern hemisphere would end up warm and dry and the southern hemisphere (which is already mostly water) would end up cool and wet. But I have very little scientific knowledge on the topic to back that up.
I also don’t have enough knowledge to speculate on how much a fast wobble would affect the Earth as far as earthquakes, tectonics, and tides are concerned.
Yes. This could be achieved using a yearly precession. Currently the direction of the Earth’s polar axis changes very slowly; sometimes it points towards Polaris, the current pole star, but the polar axis will gradually move over thousands of years, until it points at Vega and several other stars in turn. This cycle takes about 25,000 years to complete.
If we could induce a yearly polar 'wobble so that the polar axis changes in synch with the direction of the Sun, then we could maintain a fixed angle with respect to the Sun in the Northern and Southern hemispheres.
Exactly how this could be achieved is an exercise for the imagination, and I doubt it could be done without causing earthquakes and severe tides on Earth, especially if the Moon remains in the same orbit.
To compare temperatures you need to compare latitudes in each hemisphere. South Georgia at 54.4°S is very cold, while Newcastle-upon-Tyne at 54°58 N is relatively temperate. Most temperate countries in the South are much closer to the Equator than the ones in the North.
So, cooking the southern hemisphere seems to be best. We’d lost New Zealand, Australia, and the southern part of South America as habitable areas, but the highly populated areas in the north would probably get by.
I think I read once that if the Earth didn’t wobble we’d end up with temperature “bands”. Mexico would be so hot it’d be uninhabitable. Most people would have to live in the extreme North or extreme South (as in South America)
It varies a lot by plants- some decidious plants will be fine just not dropping leaves, some won’t be. Flowering is often daylength or change in daylength (technically actually night length) triggered, but it can also be temperature triggered and some plants need a winter chill followed by a temperature increase to flower (some seeds do to germinate as well, but that’s normally a lot easier to do artificially).
However, we’ve already actually bred the flowering triggers out of some crops because it makes it more efficient for agriculture, and we could probably manage it pretty easily for some others given some incentive and a bit of CRISPR messing.
We’d be losing all the cherries, apples, pears and the like for decades though, you wouldn’t be able to change an existing tree.
But that’s just crops. It would screw up an awful lot of native species, which as well as the loss in itself could have really unpredictable results for pests and disease spread for the crops we had otherwise got growing OK. Natural mutations do occur- which is where the daylength neutral crops come from- so some may eventually bounce back, but the damage would be huge.
Yes, Antarctica is large, but compare the Northern and Southern hemispheres:
Even with Antarctica, there’s a lot more water and a lot less land. That’s going to affect weather no matter what. Water circulation in particular would make a big difference. Yes, Antarctica will grow more ice that it does now, but I think the effect would be far smaller than if the Arctic and most of Northern Canada, Northern Europe, and Northern Asia were to start to freeze over.
One form of ‘Endless Summer’ that would be stable is if the Earth were to become tidally-locked with the Sun, just like the Moon is tidally-locked with the Earth. Indeed, it is very likely that a significant fraction of all the exoplanets so far discovered are tidally-locked, and always present one hemisphere towards their star.
If the Earth were tidally locked, one entire hemisphere would become icy, since the oceans would freeze on the dark side; the sunny side, on the other hand would become a large permanent weather system with deserts and rainforests arranged around the sunward pole. Because Coriolis effect would be minimal on a world with a year of 365 days, there would be little change in the weather, and no cyclones/anticyclones or hurricanes to worry about.
Here’s a fascinating projection of the climate on such a world.
First: thanks, all, for the ideas–I’m really enjoying reading this! I lack the scientific knowhow to answer the question.
Definitely–but I’ve read this idea in science fiction before, and I wanted to explore a different question, one in which we still have a day/night cycle, but our seasonal cycle is interrupted.
I just educated myself on a misconception I had. I thought the poles were colder than the equator because of the extreme winters they had, with the extreme lack of sunshine. It turns out that that’s less of a factor than the angle at which sunlight hits the poles: the oblique angle of sunlight at the poles results in a cooler climate.
So it sounds like the Arctic would heat up, but not as much as the tropical zones in the Northern hemisphere would. Those would get brutal.
Hot air holds moisture better. I wonder whether we’d get extreme humidity and precipitation in the north, with much less precipitation in a cooler south? Would cloud cover result in an albedo effect that would mitigate some of the heat up north?
The key here is ‘holds’ - higher humidity, sure, but not necessarily more precipitation if there’s never a sufficient temperature drop to release it. Or only in rain shadows, which mostly don’t need it. And places like California or India can definitely kiss goodbye to the snowpack that actually is the main source of their water.