For changes to be useful, they must be averaged so that the signal is not masked by large seasonal and daily fluctuations. The critical item is the relative consequence of the change in global averages, not the absolute values of the changes themselves since biodiversity is not uniformly distributed nor does it respond uniformly to each absolute degree of temperature difference. Likewise, the specific temperature in any particular year is not particularly relevant since there is wide variability between years as well as seasons. However, we do know one thing:
If one does compare the average rate of change during the Paleocene-Eocene Thermal Maximum with the AVERAGE rate that can be computed OVER THE PAST 150 years, we observe that the current rate is about 36 times faster. This implies that we shouldn't expect faunal changes in more recent future times to be less than what has historically occurred in the past, since there is no evidence whatsoever that somehow magically evolution that altered the mammal fauna then is acting differently now than it did 55 million years ago. Indeed, we might instead expect that extinction rates will likely be higher, particularly since there are many human induced land use changes that affect species diversity IN ADDITION TO those induced (explained by) solely climate change. Likewise, observations concerning the rate at which tropical species are now invading temperate environments are likewise consistent with those predicted based on the relative difference in average rate of warming, as well as those observed by looking at faunal changes in the past. The consequences are significant because of the disruption of ecosystems associated with such invasions, particularly when such invasions involve disease. For example, ten years ago cases of West Nile Virus in the US, were extremely rare, now they are becoming increasingly common.
If we look at previous geological periods that have exhibited temperature changes of similar magnitude associated with very rapid warming, ALL show tremendous extinction rates. Consequently, there is considerable evidence to suggest that the current rate of warming will induce similar rates of extinction.
Instead of terrestrial biodiversity, one could look at sea level rise and glacial and ice shield melting as another area of active interest since the consequences are particularly important. In both cases the averages of temperature change now being experienced unequivocally demonstrate that as the glaciers retreat, and they are retreating at record rates, and as ice sheets melt (both Greenland and the Antarctic are loosing ice volume), sea levels will rise faster than at any time in recent geological history. Although the averages are based on only about 150 years of accumulated data for temperature records using thermometers of various kinds, there is simply no reason to believe that sea levels won't rise rapidly or that the consequence of this rise will be anything less than extraordinarily expensive to humans. Within 200 years, it is likely that every port in the world will have to be rebuilt and unless checked, humanity had better get used to the idea of rebuilding all its ports every couple of hundred years. If one, computes this cost alone, it becomes clear that getting off fossil fuels will be incredibly more economical than continuing to burn them.
You ask about the temperatures since 1975 and those before 1945. One can presently only say that whatever has been occurring in the last 20 years or so is significantly different from what has gone on before because it is virtually certain that the last 20 years has been significantly hotter than the previous several hundred thousand. However, it also should be emphasized that this observation is completely consistent with an exponential nature of the curve and probably the next 20 years will likely better define what we can expect in subsequent decades. If you want to argue that things will be different than what the long term averages suggest, however shake they might be, then you will need to have actual evidence that such notions are any longer relevant. Simple, "naked" skepticism with out evidence might give the appearance of critical thinking, but that is all it does since it provides no substantive evidence that any critical thinking has actually occurred.