His conclusion was probably correct. 4 to 5 times more carbon dioxide was OK, then because there was not a huge amount of ice to melt, flooding millions of peoples' homes.
https://en.wikipedia.org/wiki/File:Phane...
"Higher levels of CO2 cause plants to produce fewer leaf stomatal pores per unit area of leaf surface, and to open those pores less widely
[Woodward 1987; Morison 1987].
This figures shows estimates of the changes in carbon dioxide concentrations during the Phanerozoic. Three estimates are based on geochemical modeling: GEOCARB III (Berner and Kothavala 2001), COPSE (Bergmann et al. 2004) and Rothman (2001). These are compared to the carbon dioxide measurement database of Royer et al. (2004) and a 30 Myr filtered average of those data. Error envelopes are shown when they were available. The right hand scale shows the ratio of these measurements to the estimated average for the last several million years (the Quaternary). Customary labels for the periods of geologic time appear at the bottom.
Direct determination of past carbon dioxide levels relies primarily on the interpretation of carbon isotopic ratios in fossilized soils (paleosols) or the shells of phytoplankton and through interpretation of stomatal density in fossil plants. Each of these is subject to substantial systematic uncertainty.
Estimates of carbon dioxide changes through geochemical modeling instead rely on quantifying the geological sources and sinks for carbon dioxide over long time scales particularly: volcanic inputs, erosion and carbonate deposition. As such, these models are largely independent of direct measurements of carbon dioxide.
Both measurements and models show considerable uncertainty and variation; however, all point to carbon dioxide levels in the past that have been signifcantly higher than they are at present. While the GEOCARB Carbon dioxide levels in the most part of the Phanerzoic Eon shows a fit and resultíng climate sensitivity similar to todays values, the early Phanerozoic includes a global ice age during the Ordovician age combined with high atmospheric carbon contents based on the same project. There have been different speculations about the reasons but no acknowledged mechanism so far."
Your question makes no sense (no surprise there). Stomatal density is only one method of estimating CO2 levels - and it is not one that climate scientists depend on. It was climate scientists who identified the method's weaknesses.
You probably should not base your insults on childrens' intelligence - scince you know less about science than most children.
LINK and are you sure this was a climate scientist, sounds more like a biologist
Scientists study what there is to be studied, it is not like they can measure CO2 in air 8000,000 years old
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their stomata after they die before being fossilized. It's a no brainer living plants in the past had much fewer stomata open compared to the number of open stomata found in fossilized plants. As a result, plant stomata proxy always far overestimate the CO2 levels in the past. There's this one guy who compared plant stomata in living plants and those in fossilized plants concluded, albeit erroneously, that CO2 level in the dinosaur era had 4 to 5 times as much CO2 as today. We know CO2 above 1,000 ppm sustained would kill all animals let alone dinosaurs. CO2 level in the air is dictated by temperature which is in turn dictated by how strong the Sun is, unless humans transport carbon from underground into the air through burning hydrocarbons. We know about 4 million years ago global temperature was at a peak when the poles were about 10 C warmer than they are now. And even then CO2 level was 415 ppm, about as much higher compared to the peak inter glacial over the past 800,000 years as the peak inter glacial over the past 800,000 years is compared to the peak glacial over the past 800,000 years. Why climate scientists make such stupid mistakes when they are supposed to be smart?
