Simply on a factual basis, the data we have from previous extinction events does not have the temporal resolution needed for us to determine how quickly the temperature increased/decreased. E.g., "how quickly did the atmospheric temperature change after the Chicxulub event?" We don't know. Decent-quality global paleoclimate proxies only extend back ~15k years or so. It's possible that there was rapid global climate change in the past outside of major extinction events; we genuinely don't have the data to tell.
This also doesn't really tell us much about how the modern Earth and its ecosystems would handle those old climate shifts, because there is much much less wild lands (and so, less resilience within natural ecosystems). It's true from a climate science perspective, but not useful for assessing the damage that climate change can cause to modern society.
And: to the best of our knowledge, the current rate of warming is fast enough to cause major issues. Civilization only arose once we had relatively stable and moderate temperatures, and stable temperatures may be needed to maintain civilization under present technology. Ecological and glaciological studies back this up. And no, scientists are not looking to just scare us into action; the evidence itself should be alarming.
According to the no doubt very reliable Animal Armageddon: Episode 3: Doomsday it would have gotten very hot on the surface (100C+?) a few hours after Chicxulub then a while after that apparently 26C colder than normal for years due to dust in the atmosphere.
Simply on a factual basis, the data we have from previous extinction events does not have the temporal resolution needed for us to determine how quickly the temperature increased/decreased. E.g., "how quickly did the atmospheric temperature change after the Chicxulub event?" We don't know. Decent-quality global paleoclimate proxies only extend back ~15k years or so. It's possible that there was rapid global climate change in the past outside of major extinction events; we genuinely don't have the data to tell.
This also doesn't really tell us much about how the modern Earth and its ecosystems would handle those old climate shifts, because there is much much less wild lands (and so, less resilience within natural ecosystems). It's true from a climate science perspective, but not useful for assessing the damage that climate change can cause to modern society.
And: to the best of our knowledge, the current rate of warming is fast enough to cause major issues. Civilization only arose once we had relatively stable and moderate temperatures, and stable temperatures may be needed to maintain civilization under present technology. Ecological and glaciological studies back this up. And no, scientists are not looking to just scare us into action; the evidence itself should be alarming.