Change in Earth Precession Axis May Add to Global Warming?

Ichon

Ad Honorem
Mar 2013
3,655
#13
But wouldn't it be different year to year?
What do you mean? The earth is roughly the same distance from the sun year to year and the sun puts out the same amount of energy year to year... those can and will change but over timescales of millions of years. If the direction the earth is angled changes the same amount of energy will hit the earth, the main difference in global temperatures would come from the ocean conveyor belts and the reflection or not from snow/ice during winter or seas cleared of sea ice. Even then though on a year to year basis those changes will be tiny but after a few decades, it would impact plant life and thus human life. After a century the oceans will not transfer heat in the same way- normally a ful ocean cycle is around two centuries last I read but that is only some of the major known currents at this particular time.

The ability of the ocean to store both carbon and heat is the main factor allowing the current widespread greenbelts to high latitudes. Change either of those and what type of life can exist on earth will also change but such things don't change much year to year and there are many feedback loops and other effect that we don't understand yet so increasing a single input might not be enough to affect the entire system unless it is the primary input (sun).
 
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M.S. Islam

Ad Honorem
Jul 2012
3,333
Dhaka
#14
What do you mean? The earth is roughly the same distance from the sun year to year and the sun puts out the same amount of energy year to year... those can and will change but over timescales of millions of years. If the direction the earth is angled changes the same amount of energy will hit the earth, the main difference in global temperatures would come from the ocean conveyor belts and the reflection or not from snow/ice during winter or seas cleared of sea ice. Even then though on a year to year basis those changes will be tiny but after a few decades, it would impact plant life and thus human life. After a century the oceans will not transfer heat in the same way- normally a ful ocean cycle is around two centuries last I read but that is only some of the major known currents at this particular time.

The ability of the ocean to store both carbon and heat is the main factor allowing the current widespread greenbelts to high latitudes. Change either of those and what type of life can exist on earth will also change but such things don't change much year to year and there are many feedback loops and other effect that we don't understand yet so increasing a single input might not be enough to affect the entire system unless it is the primary input (sun).
I was thinking region-wise. E.g. when the tilt is away from the sun, the north pole would be cooler.

Thanks for the explanation.
 

Ichon

Ad Honorem
Mar 2013
3,655
#15
I was thinking region-wise. E.g. when the tilt is away from the sun, the north pole would be cooler.
That is what happens during the seasons so yes the particular areas of the earth that are facing the sun will change temperature accordingly but it wouldn't really be global warming so much as climate change that is always ongoing- just usually so slowly a single human lifetime is not enough to perceive the changes.

The sun is the primary source of heat on earth but it also is fairly constant so when latitude average temperatures change it is usually due to factors other than the sun.

If the orientation of the earth rotates any direction away from the sun that affects daily temps as would the speed of the rotation and some other factors but the overall global temperatures are controlled more by the water cycle which does shift but without something else going on such as the degree of tilt, the length of earth's orbit (circle vs oval), the position of the continents relative to the equator (when ocean temperature conveyor currents have landmasses in the way the higher latitudes tend to be colder). If the earth tilted more than 25 degrees for example each season then the corresponding winters would be slightly longer and colder and the summers warmer and shorter. Over many years the higher latitudes would have snow accumulate without melting in the summer and building up into glaciers which then spread toward the equator as greater snow/ice reflect more of the sun's heat and that is essentially what happens in an ice age.

Far as we know there is usually more than 1 trigger for an ice age but the time scale is still very long and so we probably don't know all the triggers and we definitely don't know the importance of each individual contributing factor. Climate models build many different assumptions and weight the factors variously but so far none have been very accurate for anything other than trends on scale longer than a season.

The current warmest part of the global cycle was about 11,000 years ago which is how the last ice age ended but we are still on a relatively warm part of the cycle and if humans add enough greenhouse factors into the atmosphere we might trend toward warming again but overall the amount of water vapour in the atmosphere is about .02% of total water on earth with oceans containing 48% and the crust containing another 48% with the remaining 1.98% distributed as glaciers, lakes, rivers, near-surface aquifers. etc.

Water vapour is only a very small % of the atmosphere but plays an important role due to the water cycle of evaporation and condensation. The greenhouse gases primarily carbon dioxide and methane are even smaller part of the atmosphere in % terms but are able to absorb and store more heat than water vapour releasing it over time which is a big part of the reason why the temperature doesn't drop to freezing over the continents at night when the sun's energy is shining on the other side of the world and there are no oceans that also store many years worth of the sun's heating. Temperatures in the interiors of continents do drop much more on diurnal basis than near the oceans which is why nightly temperatures in the Sahara are near freezing during the northern hemisphere's winter while temperatures in England are several degrees warmer despite being 1,500 miles further north or roughly 6% of the circumference of the earth further away from the equator where the majority of the sun's heat hits the earth.

Global temperature factors-

#1 Sun (impacted by speed of rotation, angle of tilt or the wobble in earth's orbit and solar cycles which we know enough about to say with large certainty they are very long in human terms)
#2 Water distribution (water cycle where water can store and transfer energy more efficiently than anything else that is present on earth in large amounts)
#3 Greenhouse gases other than water vapour
#4 Altitude
#5 Latitude
#6 Location of Continents
#7 Macro weather patterns primarily influenced by ocean currents but can be steered by other factors hence not included under water distribution

Of those factors the easiest to change because of their relatively tiny proportion in relation to everything else are the Greenhouse gases. Accounting for less than .01% of the atmosphere but responsible for roughly 20 degrees difference between the heat the earth absorbs from the sun and the heat that goes back into space.
 
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AlpinLuke

Forum Staff
Oct 2011
26,829
Italy, Lago Maggiore
#16
Now, I've got a bit of expertise in this field from when I was a researcher of alternative history and I got in touch with the matter of the precession ... but I've got a passion for Astronomy and so I looked for explanations ...

Listen, the rotation of the axis of our planet can affect climate because of the distribution of the dry lands. The reaction to sun energy of sea and soil are well different: seas tend to absorb solar energy, soils tend to reflect sun energy. So that, theoretically [without changes in the presence of greenhouse gasses in the atmosphere] when our planet shows to the sun more dry land it should be colder.

Let's say this: precession is quicker that tectonic movements. Anyway if this was true, since geologically the continents we see today exist since not a few millions of years ago ... we would have recorded a quite predictable sequence of warm periods and glacial ages. I have to check this, but it seems that this hasn't been reality.
 
Jan 2009
1,264
#17
Yello.

Precession is the reason we have different seasons.
Depends a bit what you mean by that.

Axial tilt is the reason why we have seasons.

Precession would change WHEN we have the seasons. Just take a look at the illustration in your post (same one I quoted above), it explains this very well.

1. Currently (2000AD one), Summer solstice (the axis pointed closest towards the sun) is very close to Aphelion, which is the FARTHEST point in the Earth's orbit (it is not -exactly- circular, but very close).

2. In 12000 AD (8000BCE) or so, Summer solstice (see above) is actually very close to Perihelion, the closest point in the orbit. Is anything, this should mean that the Northern Hemisphere summers should be slightly hotter, since the planet is a bit closer to the Sun. I don't know where you get the idea that it should be cold all year around from precession and solar irradiance*? (Ice age is a whole another topic.)

However, the rest of the year the axis stays pointed towards the same non-sun centric direction, so you still get all the seasons. Also, if you would get warmer summers, then you should be getting colder winters, for the same reason. Also, southern hemisphere summers should be getting colder and winters warmer. Instead we are seeing temperature rise all over the globe. Finally, this is a very slow change. It takes about 23000 years to complete the cycle, meaning 360 degrees. By contrast, Climate change / Global warming is happening in human scales, the temperatures are climbing within a lifetime.

So no, precession doesn't have anything to do with Global Warming.

(* The solar irradiance change between perihelion and aphelion is actually swamped by the difference in land vs. sea area: Apsis - Wikipedia -> northern hemisphere summers are hotter than southern despite being closer to aphelion.)
 
Mar 2019
1,612
Kansas
#19
Not really a matter of opinion here. The several degrees variation in axis of revolution does lead to large climate changes, especially in temperate latitudes.
The OP seemed to be specifically referencing the poles. And the amount of energy received is not going to change.
 
Jan 2009
1,264
#20
Not really a matter of opinion here. The several degrees variation in axis of revolution does lead to large climate changes, especially in temperate latitudes.
This is a good summary of the orbital effects and the climate data on geological timescales:
Milankovitch cycles - Wikipedia

However, it is clear that the current Global Warming / Climate Change happening in the last century or so is not caused by orbital effects.