This seems like a big logical leap to me. I don’t even accept that this is true with regard to the stock market. I mean, are you suggesting Wall Streeters woukd agree with you that macro-forecasting is easier than micro-forecasting? Isn’t it true that most star fund managers in the short run end up failing to beat their benchmark in the long run? Like with the climate, doesn’t the time variable just multiply the complexity? Look at my question about technology changes alone. Just like who will be president and who will be running Congress will have a huge, unpredictable impact on the market in a decade, unforeseen changes in tech and society will have huge, unpredictable impacts on the climate (if we accept the premise man greatly impacts climate).
Weather and climate are not the same, but predicting the weather this weekend must be infinitely easier (with regard to variables) than predicting the climate in a generation. Yet the weekend weather forecast is frequently wrong — by a lot.