A third grader? That is doable:
A chicken that came from an egg last year could lay an egg this year. Neither one has to only come first.
As long as it keeps rolling down a hill, a snowball can get bigger and bigger the further it rolls. The more snow that sticks to it, the bigger it gets. The bigger it gets, the more snow sticks to it. And summer is not a hoax if Sagebrush shovels the snowball off his driveway with one great big Ha!
My attempt at the sort of answer I'm looking for:
CO2 can be both a feedback and a forcing. That means that it can change on its own--for example, by people burning a lot of fossil carbon sources. But it can also change as a result of other changes--when the world gets warmer, oceans release absorbed CO2. In fact, one of the ways we can tell that CO2 is acting as a forcing rather than a feedback right now is that oceans are *gaining* CO2, rather than losing CO2.
Water vapor is a strong positive feedback, but it is not one that can spiral off into infinity. It's more like, say, some wealthy person or company offering to match donations for a charity drive. The charity won't end up with infinite money because of the matching donations, it will just end up with about two or 3 times as much money as it raised.
Feedbacks, by definition, only *react* to something else (at least, when they're acting as feedbacks). Something can be both a feedback and a forcing (like CO2), but water vapor is not one of those feedbacks. If I sprayed a billion tons of water vapor into the air, I would end up with... fog or clouds, that would become rain or dew, likely within a few days at most. But if I spray a billion tons of CO2 into the air, it will increase the amount of CO2 in the air for months to centuries (depending on various factors)
Those explanations aren't quite at the "level" I was hoping for (except perhaps the charity-donations analogy), but, well... even when I *was* in third grade, I probably had trouble explaining things at a third-grade level (yay, Asperger's)
Basic physics says doubling CO2 will cause 1.2C of warming. With feedbacks, this number is increased in models to say whatever number the modeler would like to achieve.
However, if instead there is negative feedback, then this 1.2C of warming, itself not a big deal, becomes an even smaller amount so as to be nondisconcerting.
The magnitude of cloud feedback is not really known. and even the sign is in dispute. This number by itself changes the output of models dramatically, far more than the change from CO2 emissions of a carbon tax.
Well before you can explain it it is necessary to understand it first, negative and positive, with positive feedbacks is a process that occurs in a feedback loop in which the effects of a small disturbance on a system include an increase in the magnitude of the perturbation, Positive feedback tends to cause system instability, there will typically be exponential growth.
Whereas positive feedback tends to lead to instability via exponential growth or oscillation, negative feedback generally promotes stability. Negative feedback tends to promote a settling to equilibrium, and reduces the effects of perturbations.
Now our climate has been relatively stable throughout history, with no spirally out of control (as you say) so we can probably deduce that our climate has more negative than positive feedbacks, and therfore a small perturbation like an increase in CO2 is unlikely to cause a major disturbance.
Could someone explain negative feedback to alarmists? Oh well, just keep lowering climate sensitivity and then somehow pretend that "deniers" weren't right all along. ROFL :-D
If I did tell the truth you would have me vaporized, like you did last time. Ha! Ha!
In global warming here is how it goes. Obama gives the UN $100 billion. The UN takes 50% and feed back the rest to Al Gore, George Soros, Maurice Strong and a host of other thieves.
Now get this one vaporized. Ha! Ha!
This is quite a good introduction.
kano -
>>Well before you can explain it it is necessary to understand it first,<<
Plagiarism is stealing - and passing plagiarized material off as evidence that you understand something is lying.
NO.
I tried to explain calculus to my dog.
Was equally successful, but both of us enjoyed it more.
they are deniers. logic does not apply
There seem to be a lot of skeptic/"skeptic"/denialist misunderstandings about feedbacks. Some common misconceptions I've seen: if CO2 was a feedback in the past, it can't be a forcing now. If water vapor (or some other common thing) is a relatively strong positive feedback, then global warming would have spiraled out of control in the past, and we would be much warmer now. The idea that natural feedbacks like water vapor "drive" climate change, and therefore the impact of CO2 is negligible. And probably others, feel free to throw in explanations for any other feedback-related misconceptions you've seen.
In small words, like you were explaining it to third-graders, could you explain these things to the denialists?
