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where'd the data come from?
400K is Ice cores...
what's the rest?

I already answered this question in my previous comment

The chart is from NASA, it is explained in the video I linked. The data goes back to 800,000 years.
https://icecores.org/icecores/drilling.shtml
The oldest continuous ice core records extend to 130,000 years in Greenland, and 800,000 years in Antarctica.
Most graphs only show the last 400k years just to make the graph smaller
https://climate.nasa.gov/evidence/

All this data comes from ice cores, they have ice cores that are over 800,000 years old

what are the proxies?

Proxy temperature just means the temperature was derived from ice cores. Humans only started recording reliable temperature records starting in the 1880s

https://en.wikipedia.org/wiki/Proxy_(climate)

Proxy (climate)
In the study of past climates ("paleoclimatology"), climate proxies are preserved physical characteristics of the past that stand in for direct meteorological measurements and enable scientists to reconstruct the climatic conditions over a longer fraction of the Earth's history. Reliable global records of climate only began in the 1880s, and proxies provide the only means for scientists to determine climatic patterns before record-keeping began.
Examples of proxies include ice cores, tree rings, sub-fossil pollen, boreholes, corals, lake and ocean sediments, and carbonate speleothems. The character of deposition or rate of growth of the proxies' material has been influenced by the climatic conditions of the time in which they were laid down or grew.

see..that wasn't hard was it?

haha, not it was not hard at all, I am glad you are finally beginning to understand

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