Maggie's Farm

B. Hammer: I don’t want to get the wing nut spun up this morning, but Medieval Warm Period was warmer than now.

Local proxies don't add up to a global trend. See Neukom et al., No evidence for globally coherent warm and cold periods over the preindustrial Common Era, Nature 2019.

You might even read one of your own citations: Cahyarini et al: "It is still debated whether the MCA is a global phenomenon or more regional in extend."

That's because the warming apparently occurred at different times across the globe, which a look at the proxies would show. There probably was a heat signal moving through the climate system, but nowhere near as strong as the current anthropogenic warming, which is distinct and simultaneous across 95% of the globe.

Joe B: What were the regional impacts of climate change during thr medival warming period?

Regionally, you were periods of warming, but the warming wasn't globally-synchronous, so different areas of the world warmed then cooled at different times. The mean global temperature probably didn't rise that much, less than 0.5°C, if at all. Neukom et al: "This lack of spatiotemporal coherence indicates that preindustrial forcing was not sufficient to produce globally synchronous extreme temperatures at multidecadal and centennial timescales." It's thought the Medieval Climate Anomaly was due to changes in insolation and volcanism.

Joe B: What were the observable impacts in the region that signifanctly warmed centuries ago?

The effects varied considerably in different regions. Severe drought affected North American settlements with some urban centers abandoned, especially in the southwest. Central American and Andean civilizations were also disrupted by changes in rainfall patterns. In northern Europe and central Asia, on the other hand, the warmer temperatures resulted in increased agricultural production.

Anthropogenic warming will be of a greater magnitude and will be global in effect. Humans are much more densely populated today, especially along coastal areas. Mass migration may occur as sea levels rise and agricultural patterns change, with all the entailed political and cultural stresses.

Humans are highly adaptable, but even with mitigation, there will be some permanent loss of humanity's natural inheritance, and the economic costs will be substantially higher the longer it takes to mitigate and adapt.

Christopher B: Not necessarily

The damage from warming of 3°C will be significantly greater than damage from warming of 2°C. Delaying the switch to a greener economy is not something that can easily be made up for later.

Christopher B: It would be interesting, however, to be around when they unbury those huge pits of discarded wind turbine blades and toxic dumps full of batteries.

Batteries are economically recyclable. As you point out, new technology will be able to resolve issues, such as how to recylce turbine blades. Oh, already solved. Many blades are reused. Those past their useable life can now be recycled.

Christopher B: That assumes, of course, that we continue to make reasonable and prudent decisions and continue to see our overall level of technology and resources grow, rather than adopting the climate alarmist position that we should all freeze to death in the dark when the wind doesn't blow.

There we agree. The transition will require continued economic growth, including in developing countries, necessary to power the technological innovation required to meet the challenge.

The ecological and economic cost of any energy source should include all phases, from production to emissions to decommissioning.

Joe B: Very assertive . . .

The effects varied considerably in different regions. See Neukom et al., No evidence for globally coherent warm and cold periods over the preindustrial Common Era, Nature 2019.

Severe drought affected North American settlements with some urban centers abandoned, especially in the southwest. See Cook et al., North American Drought: Reconstructions, Causes, and Consequences, Earth-Science Reviews 2007.

Central American and Andean civilizations were also disrupted by changes in rainfall patterns. See Gill et al., Drought and the Maya Collapse, Cambridge University Press 2007; Arnold et al, Drought and the collapse of the Tiwanaku Civilization: New evidence from Lake Orurillo, Peru, Quaternary Science Reviews 2021.

In northern Europe and central Asia, on the other hand, the warmer temperatures resulted in increased agricultural production. See Ljungqvis et al., Climate and society in European history, Climate Change 2020.

Anthropogenic warming will be of a greater magnitude and will be global in effect. See AR6 Climate Change, IPCC 2021.

Humans are much more densely populated today, especially along coastal areas. See Wilcox & Jessop, Ecology and Environmental Health, 2009.

Mass migration may occur as sea levels rise and agricultural patterns change, with all the entailed political and cultural stresses. See Altschul et al., To understand how migrations affect human securities, look to the past, PNAS 2020.

Humans are highly adaptable . . . See Masey, Humans May Be the Most Adaptive Species: Constant climate change may have given Homo sapiens their flexibility, ClimateWire 2013.

. . . but even with mitigation, there will be some permanent loss of humanity's natural inheritance . . . See Malhi et al., Climate change and ecosystems: threats, opportunities and solutions, Philosophical Transactions of the Royal Society B 2020.

. . . and the economic costs will be substantially higher the longer it takes to mitigate and adapt. See Black, Climate economics - costs and benefits, Energy & Climate

Joe B: . . . contradictory . . .

That different things can happen at different places does not constitute a contradiction.