This is hard to visualize- there's a big difference between Arctic & Antarctic summer heating - peaks vary by ~12,886 years.
Think of it this way, Antarctica naturally melts while the Arctic gains ice- not just based on seasons, based on regular orbits
Stretch this out for the last 800,000 years- there's a seemingly random pattern but it's not, it's irregular but cyclical. Sometimes the Arctic gets much more summer sunlight, sometimes Antarctica does and it can be by ~20%
In one hemisphere the ice grows, the other melts.
To tie this together, why does this all matter?
Early on proxy data on global temps & CO2 content was based on Antarctic ice cores.
But as we see, there's a long time lag between Antarctic glaciation/deglaciation patterns and Arctic.
Our planet's climate isn't cut and dried, if we depend solely on older proxies, we get an irregular & colored view of climate past- but if we look at more proxies & from a greater global distribution, we see CO2 does not lag temperature.
Okay, this ain't exactly "orbital mechanics & it's implications for paleoclimate proxy data usefulness for beginners" but... I've been leading up to this; it has a very important message towards the end, here it goes.
This might come as a shock, but the Earth revolves around the sun.
And it does so in an irregular but predictable way, based on the gravitational pull the other planets have on Earth- it's irregular but predictable & it causes major changes in our orbital path.
Our orbit isn't circular but elliptical- that ellipse can be quite a bit "out of round" or it can be nearly round - we're just about as round now as it gets- only 5 million Km separates the closest we get to the sun in any year, to the farthest.
Why is this so important?
Because the poles only get sunlight roughly half of the year, and the greater the axial tilt, the "further up" the sun gets.
If your summer is when the earth is farther away, your polar ice caps won't melt as much.
This encourages glaciation.
This is a work in progress, thought it might be fun to show it before it gets full annotations.
I think there's enough info for some to "get it" but the reason is simple enough- we really live on "two worlds" when it comes to ice caps.
Global Ice Extent for 18 December, 2022. Once again the Arctic ice has barely increased, while Antarctic ice keeps losing upwards of 300,000 Km²/day.
If you aren't already familiar with Japan's brilliant VISHOP resource, here's the link. It takes a bit to get used to, but it's the earliest reporting ice source every day, always available like clockwork.
https://ads.nipr.ac.jp/vishop/#/extent
VISHOP
VIsualization Service of Horizontal scale Observations at Polar region
Here are the daily comparisons for both Arctic and Antarctic ice extent for each day in 2022 compared to the average for each day 1979-2021. This year's Antarctic data is (and will end) as the lowest in the data set, with the Arctic in 5th, and global almost certainly in 3rd. For today's date (Dec 17) the global total is the 2nd lowest ever and there is a chance by the end of the year, we will have the lowest total global daily extent.
Source:
https://masie_web.apps.nsidc.org/pub//DATASETS/NOAA/G02135/seaice_analysis/Sea_Ice_Index_Daily_Extent_G02135_v3.0.xlsxUntil Mauna Loa observatory returns to action, I'm going to use NOAA's global CO2 measuring system as my benchmark.
For the last week, CO2 levels are up 0.26PPM. This week's data is 1.84PPM higher than last year's the cumulative increase is the lowest for this date in the last 10 years.
let's tighten up on a shorter time frame, just the last 310:
It has varied annually by a maximum of roughly ±1 part in 2000.
But what clearly has varied at least in the last 220 years where we have much better data, are greenhouse gas concentrations.
We're adding every decade ~ equivalent of 1/1000 of the sun's energy.
That is well distributed, not just sun drenched parts of the world
I've left an additional almost two centuries of history, but that will be addressed in the future!
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We are currently in a period of "a quiet earth" (Milankovic chart, in blue)
The people who mistakenly believe climate science is a scam, are always searching for alternative explanations for natural parameters that might explain what we are currently seeing.
Here is 8700 years of our sun's output, compared to CO2 levels and surface temperatures.
It's clearly not the sun, the sun has been flat for most of that 9,000 years.
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Still, almost all of that energy originally came from the Sun.
Greenhouse gases prevent the return of the energy of the earth has absorbed from the sun, back out into space.
Earth's surface energy is regulated by the greenhouse gas effect.
This is where it gets scary, Venus's very dense atmosphere has less incoming sunlight than the earth does.
The top of Venus is atmosphere receives twice as much solar energy, but very little of it reaches the surface. It is reflected away.
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This is a diagram of Earth's energy budget, it's very complex!
Only ~70% of sunlight reaches the surface, but 119% of that solar component is greenhouse gases.
This is a startling concept, it means for every watt per meter squared of sunlight that reaches the surface, roughly 1.5 watts is created by the interplay of atmosphere and surface.
Greenhouse gases are responsible for 60% of the energy currently warming the Earth.
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