In the satellite era, we get very high, regular sample rates across almost the entire planet. This guarantees capture of minimums and maximums (like minimum pressure of a hurricane, or peak rainfall.) The graph above shows a sine wave with an adequate sample rate.
Looking at the same function with a lower, irregular sample rate – we see that the peak value is lower. This is analogous to collection of weather data prior to satellites and radar. Besides temporal sampling rates, another problem is the lower spatial sampling. During the 1930s, many mid-Atlantic hurricanes were probably missed entirely because there weren’t any viewers to report them.
Some scientists seem to be unable to comprehend the difference between more extreme weather data, and more extreme weather. If a 1935 hurricane were measured today, the minimum pressure would almost certainly be reported lower, simply because of the ability to sample data regularly on a finer grid, with finer time resolution.