Let's say that I measured a temperature rise of 0.1C between 8am and 8:00:0.2, every day consistently. Extropolating that leads you to conclude that everyone would be cooking by noon. "OMG, that's the end of the world!!!!" We must do something about it, right?
In the absence of any other data than those 0.2 seconds perhaps. And if you could show a 0.1 degree temperature rise
simultaneously around the whole planet in just 0.2 seconds, that would mean a staggering amount of energy being released and everything we think we know about the Earth would have to be scrapped. So yeah, I would say that would be pretty damn important.
But the flaw here is that we have an everyday experience that tells us that small variations over short timescales don't matter. We don't have that sort of direct experience with climate over hundreds and thousands and millions of years. We need models.
If you look back at the earth's temperatures, you will see lots of ups and downs - we call them ice ages. Between ages, you have warming up and cooling offs, for reasons we don't fully understand.
If you look at the long-term tread, we are now below the average temperature for the earth. So we should see some reversion to means -> temperature rises.
Why "should" we see a reversion? We've rolled ones four times in a row, so now we're due for a six? The argument assumes that there is something like a natural equilibrium that the planet naturally strives towards, and not just a bunch of random changes piled upon each other. What's the mechanism for that?
The more parsimonious explanation is that such changes happen for a variety of unrelated reasons, and that rising temperatures now are due to basic physics, not some magical gamblers-logic Gaia BS.
And, of course, we can't send thermometers back in time. The reason we know that temperature was different is in part due to - you guessed it - climate models.
So can we agree that climate models do tell us something important about temperatures?
Sure, CO2 will have an impact on temperature but we don't know exactly how. For example, CO2 is a fertilizer to plants. More CO2 + high temperature means better plant growth -> bigger carbon sinks -> a negative feedback.
We know pretty well what impact CO2 has. Higher temperatures, as you mentioned.
More plant growth does not imply negative feedback, recall this thing called the "carbon cycle" that you probably read about in biology class. For there to be a sink, you need plants to grow,
and then be taken out of circulation. If you just grow more trees, they still eventually fall down and decompose, releasing the carbon back into the atmosphere.
To say that we know little about planet earth is an under-statement. Only fools like those tree huggers and climate fanatics don't understand that.
And to say that we therefore know nothing is nonsense. We
do know that CO2 traps heat (since the 1800s!), and that more CO2 will trap more heat.
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