We know with 100% absolute certainty that a 2 degree C rise in global temperature will not cause an environmental catastrophe on a global scale.
Bold statement? I don’t think so. From about 9000 years ago to about 5000 years ago global temperatures were about 2 degrees higher than today (with a lower atmospheric CO2 level than today). We also know that virtually every species alive today was alive 5000 years ago. There have been some extinctions in recent times, mainly of island species due mostly to introduction of such things as rats and cats and rabbits but there have actually been very few extinctions of continental species and those extinctions are anthropogenic and not related to climate change.
We also know with 100% certainty that a 5 degree C rise in global temperatures will not cause an environmental catastrophe because the warm interglacial period before the latest ice age glacial period was 5 degrees warmer than today. Practically every species alive today was alive during that period as well.
In addition, we also know with 100% certainty that a 2 degree drop in global temperatures would cause a catastrophe. Many areas of the world that are currently farmed would be unable to produce a crop as the growing season would become too short. The problem with a “2 degree drop” is that it is not evenly distributed across the globe. There would be little difference in temperature in equatorial regions and the majority of the change would be felt at high latitudes. 2 degrees makes the difference between frost and no frost for many nights. We would likely see failures of citrus crops in California, late or early frosts in the Northern plains and in Canada, Russia, and China.
We can adapt quite easily to warmer temperatures. Warmer global temperatures generally mean little difference in tropical regions but significant differences at high latitude where growing seasons would become longer with more days free of frost. That does not take a lot of adaptation. Adaptation to cooling is painful and means people go hungry.
History shows us that the periods of cooler temperatures are times of famine, political upheaval, mass migrations of peoples, plague, and decreases in global population. Warm periods tend to be periods of stability, discovery, increasing wealth of the general population, and a time of increasing population. The Roman Empire expanded during a warm period and collapsed during a cold period. Groups such as the Goths, Visigoths, and Vandals migrated from Scandinavia and the Baltic Sea region to areas of the South and invaded the areas held by the Romans. In the “Little Ice Age” we saw the loss of the Greenland colonies, many of those farms are still buried in permafrost today. The population of Iceland was greatly reduced. The Great Famine reduced populations of some parts of Europe to levels not seen again until the 20th century.
I fear a couple of degrees of cooling much more than I fear a couple of degrees of warming.
The record is there. Don’t take my word for it.