Early explorations of the Antarctic report an ice free shore in areas now long covered by a growing icecap. Twenty first century science just simply lies in your face about this, with blatant barefaced fraud, but sometimes the discrepancy becomes glaringly and embarassingly obvious.
What about the North Pole? Early twentieth century attempts to reach the North Pole were frustrated by the fact that ice coverage was fragile, incomplete, and had gaps full of open water even in the middle of winter, so that travel by dog sled was dangerous and impractical. There was too much ice for it to be safe to sail to the pole in summer, but not enough for it to be safe to dog sled to the pole in winter. Today, the North Pole in the middle of winter is solidly ice bound, and it is quite easy to reach the North Pole by dog sled. So today’s north pole has a lot more ice than it did at the start of the twentieth century. The Northwest passage was difficult and unsafe for wooden ships then, and difficult and unsafe for wooden ships now.
But do we have any proxies for temperature that cover the present day, and also centuries past?
Yes we do, we have Law Dome, a pile of ice and snow in the Antarctic. Drill in Law Dome, and the isotope ratio agrees very well with recently measured present day temperatures of the weather station near Law Dome, unlike most proxies favored by global warmers.
And the Law Dome shows that in 500AD-1000AD, the temperature at Law Dome was a whole lot warmer than the present, or any recent temperatures. On the whole, temperatures have gone up and gone down, plenty of climate change, but mostly in the direction of colder, as we would expect from the growth in the icecaps.
What about surface instrument readings which supposedly show the world has warmed 0.6 degrees in recent decades?
I myself attempted to reconstruct recent global temperatures from surface instrument readings, and the data is unsuited to the task. It contains various sources of systematic error that have to be corrected by ad hoc guessing, and one can make one reasonable set of guesses and use one reasonable procedure, and get one past temperature, or a different reasonable set of guesses and a different reasonable procedure and easily get a result 1.2 degrees different without intentionally torturing the data.
We now have satellites that do provide accurate world wide readings of temperature, and have had them since 1998 (actually a good deal earlier than 1998, but the early satellites had problems that arguably make their readings non comeasurable. Debates about how earlier satellite measurements should be interpreted are difficult to resolve.)
And surprise surprise, since we have had accurate satellite readings of global temperatures, they have been fairly stable, with no obvious trend in any particular direction. There has been plenty of quite dramatic climate change in the past, and there will likely be plenty of quite dramatic climate change in the future, but it is not apparent that we have been having much climate change from nineteen ninety eight to the present.
The only data suitable for detecting small world wide variations of temperature is the satellite data, and the less one is free to torture the satellite data, the less it it indicates that anthropogenic warming is detectable.