The "proof" of many scientific theories lies in the reliability of the results that can be predicted based on that theory. If a theory is correct, predictions should be consistent, and then those predictions should be confirmed by observations.
That has left climate change scientists in a bit of a pickle. Studies predicting the future effects of warming based on studies of past temperature records have been predicting less future warming than studies based on climate models. This also leaves political decision-makers in doubt: what effects can realistically be expected in 30 years, or 70 years?
Which brings us to those who want us to believe that climate change is a myth. The first commenter under an op-ed calling for prosecution of climate deniers reminds us:
"Computer model have been grossly inaccurate and are not a substitute for empirical studies [sic]."
One can hardly blame those whose interests would be harmed by serious action to avert global warming for grasping at such inconsistencies. Will they stop grasping and accept the truth now?
A NASA-led study has found that "almost one-fifth of the global warming that has occurred in the past 150 years has been missed by historical records due to quirks in how global temperatures were recorded."
The problem arises from a couple of fundamental issues with older temperature records. First, they under-represent the climate in Arctic regions where measurements are difficult to make. Because the Arctic is warming faster than the rest of the Earth, the missing data underestimates the effects of global warming.
Second, the historical record mixes air and water temperature records, while models deal with air temperatures only. Finally, there used to be more ice. So there were more temperature readings taken over icy areas while later observations were based on water temperatures. Water warms more slowly than air, so these two issues also lead to cooler predictions based on historical data.
When the scientists ran modern climate models using historical data that was limited to measurements analogous to modern temperature records, their results landed smack in the middle of the range of predictions calculated by the models of the IPCC (Intergovernmental Panel on Climate Change).
Scientists were aware of these issues before, but this is the first time the magnitude of their effect on the predictions has been studied. As noted by lead author Mark Richardson, "They're quite small on their own, but they add up in the same direction. We were surprised that they added up to such a big effect."
Read more in the article Reconciled climate response estimates from climate models and the energy budget of Earth in Nature Climate Change, 2016; (DOI: 10.1038/nclimate3066).