> The only mild risk from mild warming is rising sea levels. That has been documented to be holding steady at 1 foot of sea level rise per century for the past few hundred years. Much smaller than the meltwater pulse at the Younger Dryas 12k years ago. Humans have continually delt[sic] with sea level rise since we invented agriculture.
That is just completely wrong. Global sea levels have been documented and reconstructed and cross-checked better than radio-carbon dating. There are still extant coastal cities that have existed for more than a thousand years, and they are all in agreement that this claim of 1 foot per century just cannot possibly true. I literally have no idea where you got this, I've never seen anyone even suggest this number. Even documented sea level rise since 1900 has been only 5 to 8 inches. Did sea level rise drastically slow down the last century? It's funny, that number, because since the 1990s the incredibly accurate modern gauges of sea level have noticed that the rate of rise has actually tripled to 3 millimeters a year and is still accelerating! That's funny, that's roughly a foot a century. So you just happen to suggest that the exact, current rate of sea level rise is the average over the "past couple centuries". Uh, no. If we were to project that 1000 years into the past, sea level would have been 10 ft lower! Corals and sediments don't lie. Sea level has been stable for 2000 years, just the perfect amount of time for modern civilization to up and build megacities on coasts the world over. Now, project that 3 millimeters per year into the future. In 1000 years, 10 feet! Goodbye all of Florida, Manhattan, and pretty much every major coastal city. But it won't be 1000 years. Things are picking up. We'll get multiple feet of sea level rise this century.
https://ocean.si.edu/through-time/ancient-seas/sea-level-ris...
The climate went through an ice age for most of the past 1 million years. As you point out in #3, an ice age glacial is infinitely worse for life on earth than mild warming. The climate prior to the Quarternary period was better for life in almost all respects. The ice age was brutal, caused mass extinctions, and nearly decimated humans as well. It also froze up so much water that virtually all of Canada and most of Russia was buried under a mile thick ice sheet. So of course, sea level was 400 meters lower than present. Much of that melting occurred with the onset of the Holocene, which has been the prevailing climate regime for only the past 12k years or so. At some point during the ice age, CO2 levels also dropped dangerously low, to 180ppm, a near record low for life's entire existence on this planet. Below 150ppm, plants die entirely. Their productivity and growth is hampered by both freezing temps and low CO2. It was so low plants could not grow at all above certain elevations that are covered in alpines today.
CO2 is not dangerous for life on earth. It is a fundamental nutrient for plant life. The optimal periods for life on this planet have all been marked by an abundance of CO2. The only mild risk from mild warming is rising sea levels. That has been documented to be holding steady at 1 foot of sea level rise per century for the past few hundred years. Much smaller than the meltwater pulse at the Younger Dryas 12k years ago. Humans have continually delt with sea level rise since we invented agriculture. It's not the doomsday event it is painted to be and the trend has not accelerated in some sort of feedback loop as was claimed 30 years ago. The trends are linear, not exponential.
I wish I could say with certainty that we have disrupted the 100K year glacial cycle. That would be incredibly good news. Unfortunately, volcanoes have a way of ruining the party. There is absolutely no evidence that a volcanic cycle cannot kick in at any moment and plunge earth in a continual regime of thick dust and particulates that increase condensation, reduce solar irradiance, and cause temps to drop by 5-10 degrees globally for the next 100K years.