Thanks for the info. I'm sorry, you were right, that was a bad source.
However, the rebuttal surprisingly leaves out a graph that directly shows temperature against glaciation, solar output and co2, but rather just talks about the comparison, without showing it. I don't find that particularly convincing of anything. Just because
> "Around 446 million years ago, volcanic activity dropped while rock weathering remained high."
it doesn't follow that
> "This caused CO2 levels to fall below 3000 ppm, initiating cooling. It turns out falling CO2 levels was the cause of late Ordovician glaciation.",
especially given that this simple graph of all 3 influences mentioned (sun output, glaciation, and co2 levels) against temperature isn't included. Do you know of a source that shows this?
> "So we see that comparisons of present day climate to periods 500 million years ago need to take into account that the sun was less active than now. What about times closer to home? The last time CO2 was similar to current levels was around 3 million years ago, during the Pliocene. Back then, CO2 levels remained at around 365 to 410 ppm for thousands of years. Arctic temperatures were 11 to 16°C warmer (Csank 2011). Global temperatures over this period is estimated to be 3 to 4°C warmer than pre-industrial temperatures. Sea levels were around 25 metres higher than current sea level (Dwyer 2008)."
Again, it's hard for me to take this seriously without seeing the comparison between the different forces that are identified against each other and temperature. It's like someone was peering at something through binoculars and said they saw an elephant. They offer as proof by stating, "I see a trunk, and a tail, and its tusks..", but they won't let you look through the binoculars yourself. (Also the Csank 2011 link gives a 404)
The best I could find was https://www.co2levels.org/, which if you click the buttons in the top left, can be massaged in displaying co2 vs temperature for the last 800k years. And even in this period there are a few the temperature decouples from the co2 levels and mostly the temperature rise precedes the rise in co2, which makes one think that co2 entering the atmosphere is a effect of climate rather than a cause.
> You have to understand geology to be able to compare. If you don't, people with agenda will easily sell you worthless graphs. Worthless as in "CO2 was higher when there were no plants and animals on the land at all, just the naked rocks." Nice target you have.
I'm not saying the earth was the same as before. Just that the idea is that co2 is causing irreversible warming and that's that, isn't supported very well by the evidence I've seen. At best what you have given me shows that the co2 causing warming isn't entirely disprovable.
I guess what I'm worried about is that the news often simplifies complex topics to, "it's a disaster!", or alternatively, "it's a hoax!" I don't think things are that simple, yet I haven't heard from anyone, scientist or no, that things are not either a "disaster" or a "hoax".