[tempestn]

The relationship between greenhouse gas concentration and heat transfer is logarithmic, not linear, so it's not surprising that we don't see a linear relationship between CO2 concentration and temperature rise. Also, once again, greenhouse gasses affect heat transfer, which affects the rate of change of temperature, rather than temperature directly. That's my basis for the claim that the full effect of the gasses being released now is yet to be seen. Finally, temperature is noisy and in the short term is impacted by many factors, so looking at a short term (in geological terms) graph, an increase may not seem large compared to the noise. However, if you look at the recent increase on a longer time scale, you can see that it is unprecedented. And it is entirely consistent with what is scientifically expected based on atmospheric CO2 levels. If you'd like to understand why more deeply than my outline here, this is a good primer: https://skepticalscience.com/empirical-evidence-for-co2-enha...

I'm always open to new information. I'm no expert in this stuff, so I can certainly learn more—learned a couple of details while reading to try to fully answer your question actually. And it's a reasonable question why the temperature increase over the past 100 years (in particular broken into two periods) isn't proportional to the C02 increase over the same time. I think I've fully answered it now though; is there anything specific that I wrote above or that's included in that link that you dispute?

[ThomPete]

No it doesent explain it. I know the answer but its not convincing and no the models so NOT actually predict anything without the curve fitting. They are more wrong than right. Yes its logaritmic but question is how much of the increase is man made how much is natural. This is the question we cant answer. If 10% of the change is caused by humans its a very different thing than if 90% is human as one scenario means we can do something and should, while the other mean its waste of time. As long as that number isnt clear i wont loose my sleep over it.

[tempestn]

OK, I'm not sure why you're not convinced. It seems to me that at the heart of it, if we massively increase atmospheric CO2, we know that atmospheric CO2 causes a greenhouse effect, and we do indeed see temperatures rising, then by far the most likely explanation is that the CO2 is causing the warming. We should require good evidence to the contrary to not accept that as at least a working theory. What's more, reducing the atmospheric CO2 will decrease warming, even if there is some other, unknown factor that is also contributing. And given that just a couple degrees of warming will cause mass extinction as well as likely significant human suffering, it would be prudent to act to counter it, even if it were actually unlikely that humans were the cause (which again, I have no reason to suspect).

So, as someone who seems eloquent and informed, your position is truly perplexing to me. The only explanation I can think of is that you have some vested interest in believing as you do, be it conscious or otherwise. Do you feel that accepting human-caused climate change would be betraying your political affiliations? Or is your livelihood, or those of close friends or family tightly coupled to the fossil fuel industry? Do you tend to distrust scientific evidence in other areas?

You don't need to answer these questions, but maybe ask yourself if there might be another reason why you're resistant to the most likely explanation here.

[ThomPete]

The heart of it is that we don't know how much humans affect the temperature increase.

If we don't know that then how can we know whether we can do anything about it?

[ThomPete]

And yes I have vested interest. My children who I don't want to grow up in a world that is based on hysteria and so I do what I can to teach them not to just be reactive and listen to the media without understanding the underlying data and to make sure they ask the right question.

The right question is to figure out how much humans affect the climate.