
Originally Posted by
Halsu
Whatever the temperatures are at any given point without human influence. Earths temperature of course varies naturally, and that variation hasn't stopped. The problem with the current situation is that we are running an uncontrolled climate experiment that offsets the natural variation, adding significantly to the energy balance of the earth.
Yes it has. But not while there has been reasonably big human civilization.
I wouldn't bet on that.
That's just plain stupid. Not even worth an answer really.
Yes. So what?
We are talking all in all about just a few percent rise in the strength of the greenhouse effect, not about doubling it or somesuch nonsense. Without greenhouse effect, earth's average temperature would be about -18 degrees celcius. With the greenhouse effect, it's about +15 degrees celsius. The total net warming effect is about 33 degrees celsius.
Even if CO2 was only responsible of 9% of the effect (the lowest estimate - about 3 degrees), doubling CO2 would make for another 9% rise in the greenhouse effect – which would cause warming of around 3 degrees, if things were linear. But they are not.
The direct effect on greenhouse effect by doubling CO2 is actually estimated to be less than that, AFAIK largely because some frequency bands CO2 affects are already saturated. But it's not as simple as that either: warming temperature will increase the amount of moisture in the atmosphere, so there's a positive feedback (water vapor isn't the only, but probably most significant of these). So, increasing CO2 will indeed also increase water vapor. All the forcings combined, the current best estimate for the effect of doubling CO2 in the atmosphere is actually pretty close to that 3 degrees.
The warming so far, about 0,75 degrees since pre-industrial times would need roughly 2% stronger greenhouse effect (using crude in-my-head calculus: the actually science is more complicated than that). Adding 50% to the concentration of a gas which has total effect of at least 9% sounds like a rather plausible reason for such a small increase, don't you think?
Of course, it's not the only way we affect the climate, there's the other gasses we emit (some of which actually cool the atmosphere), changes in land use etc.
Because the 100% change may require only 2% increase in the greenhouse effect.
Actually, it seems that in the last few decades, human influence has likely been MORE than just 100% of the warming: the natural drivers of climate (sun's activity, multidecadal oscillations, volcanic activity etc.) would indicate a cooling trend if there was no human influence. So in addition to the measured warming, it seems human influence has also offset the cooling by natural causes.
We're talking about at least a degree or two over the next 1000 years, possibly more. I do not know where you got that price tag, but to me it sounds rather silly too. Anyway, if cost is the only thing you're concerned about, the current best estimates are that preventing additional warming now is actually cheaper than adapting to it later.
Dinosaurs probably liked it. Current species would not. Getting jurassic-like climate in a transition period of anly a few hundred or so years would mean mass extinctions, and very likely collapse of human civilization as we know it too. I think you're vastly overestimating the capability to adapt to change.
That's probably true. The best way to reduce population is to educate, especially women. I'm all for that.
The real numbers are closer to instead of 3-4 degrees it will warm only 2 or so degrees. That's a difference between something that can still be adapted to somewhat reasonably, and something that's a real catastrophe.
Slowly going up is way better than going up fast.
As said, the target is to keep the warming under 2 degrees. At current course of action, we will likely miss that.
The number so far is around 0,75 degrees celsius. The range in the next hundred or so years varies between at best around 2 and at worst maybe 6 degrees, depending on what we do.
If those numbers sound small, remember that the average global temperature in an ice age is only about 5 or so degrees lower than currently. Small sounding changes have a big effect.