"But there have been several times in Earth’s past when Earth's temperature jumped rapidly, in much the same way as they are doing today. Those times were caused by large and rapid greenhouse gas emissions, just like humans are causing today. In Earth's past the trigger for these greenhouse gas emissions was often unusually massive volcanic eruptions known as “Large Igneous Provinces,” with knock-on effects that included huge releases of CO2 and methane from organic-rich sediments. But there is no Large Igneous Province operating today, or anytime in the last 16 million years. Today’s volcanoes, in comparison, don’t even come close to emitting the levels of greenhouse gasses that humans do.
Those rapid global warming events were almost always highly destructive for life, causing mass extinctions such as at the end of the Permian, Triassic, or even mid-Cambrian periods. The symptoms from those events (huge and rapid carbon emissions, a big rapid jump in global temperatures, rising sea levels, ocean acidification, widespread oxygen-starved zones in the oceans) are all happening today with human-caused climate change. The outcomes for life on Earth were often dire. The end Permian extinction saw around 90% of species go extinct, and it left tropical regions on the planet lethally hot, too hot for complex life to survive. The Triassic extinction was another, one of the 5 biggest mass extinctions in the geological record. Even in the end Cretaceous extinction, in which dinosaurs were finally wiped out by an asteroid impact, a major global-warming extinction event was already underway causing a major extinction within 150,000 years of the impact. That global warming 66 million years ago was due to catastrophic eruptions in India, which emitted a pulse of CO2 that sent global temperatures soaring by 7°C (13°F).
So yes, the climate has changed before, and in most cases scientists know why. In all cases we see the same association between CO2 levels and global temperatures. And past examples of rapid carbon emissions offer no comfort at all for the likely outcome from today’s climate change."
Those rapid global warming events were almost always highly destructive for life, causing mass extinctions such as at the end of the Permian, Triassic, or even mid-Cambrian periods. The symptoms from those events (huge and rapid carbon emissions, a big rapid jump in global temperatures, rising sea levels, ocean acidification, widespread oxygen-starved zones in the oceans) are all happening today with human-caused climate change. The outcomes for life on Earth were often dire. The end Permian extinction saw around 90% of species go extinct, and it left tropical regions on the planet lethally hot, too hot for complex life to survive. The Triassic extinction was another, one of the 5 biggest mass extinctions in the geological record. Even in the end Cretaceous extinction, in which dinosaurs were finally wiped out by an asteroid impact, a major global-warming extinction event was already underway causing a major extinction within 150,000 years of the impact. That global warming 66 million years ago was due to catastrophic eruptions in India, which emitted a pulse of CO2 that sent global temperatures soaring by 7°C (13°F).
So yes, the climate has changed before, and in most cases scientists know why. In all cases we see the same association between CO2 levels and global temperatures. And past examples of rapid carbon emissions offer no comfort at all for the likely outcome from today’s climate change."
https://skepticalscience.com/climate-change-little-ice-age-m...