Yes there are. Scientists compare the measurements from both methods in the time when there's data from both. For example ice cores formed last decade should match direct temperature measurements from last decade. It's the same way the oldest rings from living trees are matched against the newest rings from tree fossils, and radiocarbon dating is checked against all of that.
That does not look very reliable to me, because that implies certain things are only affected by ambient temperature.
Btw, Can you tell me how ancient temperature is measured from ice cores? My lookup only says we can detect atmospheric composition, and not temperatures from the ice cores.
>Past precipitation can be used to reconstruct past palaeoclimatic temperatures. δD and δ18O is related to surface temperature at middle and high latitudes. The relationship is consistent and linear over Antarctica[9]...
I think this is also flawed, because this computation requires the ratio of the isotopes in the atmosphere at the period of interest, which we don't have. And the people making this measurement just seem to assume it would certain value derived from the present, which is also unreliable...
So yea, all things considered, pretty unreliable..
It seems like you're on the trajectory to refuting all historical measurements altogether. In that case, I can't help you. Good luck. I suggest the philosophy of Last Tuesdayism, it may interest you.
I only reject using them for certain things that require vastly more reliable data. And I am not making the mistake of relying on unreliable data just because it is the best we can manage.
Also why don't you answer my question about ice cores?
> I'm not sure how you can make that claim with only 29 years of data without making some pretty big assumptions about the underlying distribution.
Under what circumstances would 29 years be an insufficient mean to compare to the last few years? Precisely those circumstances in which the climate had changed.
Under any sane statistical model. If we assume that this is a naturally occurring once in century El Nino under an equal probability model we'd expect not to see it before we have 70 years of records.