>>13753012>direct observationUsing methods that barely existed half a century ago. My point on the novelty of the methods still stands.
>the atmosphere is well mixedBy that argument the entire would would be roughly the same temperature. Most atmospheric heat transfer from one region to another is convection, after all. Yet that doesn't give this result. The non-uniformity of the temperature betrays a non-uniformity of the atmospheric matter being measured. This in turn permits non-uniformity in the distribution of CO2 and other matter as well.
This is confirmed in e.g. estimates based on satellite imagery:
>https://www.nature.com/articles/nature.2014.16615.pdfwhere differences in local CO2 measurements fluctuate in a range of nearly 5% of the reported average.
It seems like a small fluctuation, and perhaps now it is, but this beggars the question: was this fluctuation higher or lower in the past? If you only have one type of proxy (e.g. ice bubbles) you can't determine this, especially when your proxy only occurs in certain parts of the world (the cold parts). And if you can't determine this fluctuation, you can't tell if the proxy itself is actually representative of the CO2 levels as a whole at that time. You're basically just doing a nearly linear extrapolation for everywhere else.
...And linear extrapolation is the smallest of small brain analysis, especially in a system as complex as an entire planet's climate.
>We can directly observe right now what is causing global warming. We don't need proxies!Yes: increased radiative forcing is (mostly) causing global warming. But to determine whether the CO2 that's apparently causing this forcing is actually human caused, you have to look back a LOT further, which is where proxies come in.
>doomsday scenarioIt doesn't matter what the exact scenario is. What matters is that climate scientists are stating it will occur before 2100 or so, and that it's going to destroy the ecosystem, agriculture, coasts, etc.
