Are you basing this on William Connolley's revisionist climate history at Wikipedia? Both the Minoan, Roman and Medieval Warm Periods were warmer than what we are experiencing now, nor were they just regional events. Curious that the most rapid advances in technology have occurred in the past 150 years, when it has supposedly been the warmest ever.
Photosynthesis is not in danger.
A warmer earth does not mean that Europe, North America or Northern China were, or will be, experiencing tropical temperatures. Temperatures moderated, overall, with most warming occurring as reduced minimums (still well below 0) in the Polar regions, as is happening now.
Higher latitudes have an advantage in food production because there is greater landmass there. Tropical agriculture is very productive, and has been historically. It lends itself better to intensive agriculture. Southeast Asia has been a major supplier of rice for China and India since the 1500's.
I do not recall any discussions of human induced cooling or SO2 back in the 70's. The concern, and not an unreasonable one, was simply a return to an ice age, as happens every time we go into a period of cool years. That concern spawned the fear of Nuclear Winter, as though plain old Mutually Assured Destruction was not terrifying enough.
The sincere folks at the Union of Concerned Scientists felt they needed more leverage for their political efforts to ban nuclear warheads in Europe, something that would scare those who lived in countries outside the probable blast and radiation zones. Of course, when a proposal was made to test their models with real science, they blocked it. They were just warming up (pun intended) for their next escapade.
Now, if Milankovitch Cycles drive Ice Ages, would they not logically also drive Not Icy Ages? Additionally, if solar radiation is the primary driver of climate change, wouldn't variations in solar output be as, or more, significant as the position of the earth to the Sun? Food for thought.
Records show that we are not experiencing more frequent or more severe weather events than in the past. Climate change has no effect on tsunamis/tidal waves.
The elevated levels of CO2 have been most beneficial in increasing crop yields and tree growth, globally. Algal blooms are usually triggered by large influxes of nitrogen and/or iron. The nitrogen is probably human caused, but the iron is blown over the ocean by the trade winds Not so recent studies claim that iron rich dust from the Sahara has been essential to the health of the Amazon forests for millennia.
There is far more that we do not know about weather and climate than what we do know. The current climate hysteria is based on conjecture and unproven models. It has become a belief system with no room for doubt or discussion. Blind faith has become science and scientific diligence is labelled heresy and denial.
I understand the desire to live an idyllic existence, but please don't try to force the rest of us into it by relentlessly harping on about the end of the world. Ehrlich and Hansen have revised their end-of-days dates as often as a cultist preacher. I can't really blame them. Claiming that, "The world is ending unless you do what we say," has been a successful scam for generations. It doesn't make it any less disappointing that people still fall for it.