Why don't ice core samples show mt. Vesuvius eruption? ?

Mt Vesuvius, like all volcanoes, typically erupts many times. It famously erupted over 2000 years ago. Sediments from those eruptions should be included in ice core samples. Although Vesuvius is famous, it wasn't that big of an eruption on a planetary scale. It just happened in the dominant Roman Empire so it is historically significant. A very large eruptions, such as the Pinatubo, will typically cool the climate for a year or two due to sulfur compounds. The CO2 from the eruption wouldn't be significant enough to be shown on ice cores. Ice cores are taken from ice that builds up from snow over hundreds of years. It literally takes a hundred years to form a fern which is snow packed up enough to trap the bubbles. While it is forming, the gas is free to exchange with the atmosphere. Because of this, it isn't really possible to see short term events in ice core's IMO.

I don't know about the growth rings with giant sequoias. There was a warm period 2000 years ago and warmth is one of the factors that can cause tree rings to grow wider. They are function of how well the trees are doing. If they are healthy and grow well, they have wide rings. I have read that Grizzly bears and other predators feeding on salmon and depositing their waste as well as dead salmon decaying and providing nutrients is one reason why Sequoias and Red Woods grew so large. The trees are feeding off the abundance in their environment. Our CO2 emissions also lead to thicker growth rings. It is a problem when trying to use tree rings to prove we have caused warming. It was part of the fraud of Mann-made climate change. Michael Mann tried to manipulate tree ring studies to show a "hockey stick. " It was BS IMO and mostly debunked and discredited.