On the population question, my answer is simple. Increased prosperity takes care of the population problem. The socialist third world and Islamic dictatorial hellholes have population problems, we don't. Free trade helps the third world escape their poverty so they won't overpopulate.
For the CO2 (carbon) question, I'm not sure CO2 causes enough warming to be concerned about. If warming is a concern (from all manmade sources), then there are much cheaper solutions than cutting back CO2 production. We could, for example, reproduce the cooling effect of a volcanoe with high altitude sulfur.
Because of your third concern, unintended consequences, I suggest we do nothing until we have greatly improved our models, and then only encourage slight changes in behavior on an individual level based on clearly modeled consequences. Politicians will want special interest solutions and solutions with central control and lots of unintended consequences since those don't matter in the next election. My thoughts on models are here: http://shpud.com/myths.html#models
Oops, you say volcano, I say volcaaahnoe.
Because of your third concern, unintended consequences, I suggest we do nothing until we have greatly improved our models,
And your solution to halting log rolling politicians on a collision course with doing otherwise? This issue does not stop with your mere suggestions.
For ultimately, this debate is not about science, it is about politics using pseudo science & extreme exaggeration as a driver for political action to implement underlying social and political agendas.
"The urge to save humanity is almost always a false front for the urge to rule."
"The whole aim of practical politics is to keep the populace alarmed (and hence clamorous to be led to safety) by menacing it with an endless series of hobgoblins, all of them imaginary."
-- H. L. Mencken
We could, for example, reproduce the cooling effect of a volcanoe with high altitude sulfur.
Then again, we might end up doing the wrong thing there. Unintended consequences flow from ignorance and overlooking the minor roots of the equation.
A lesson to be learned from Venus:
http://www.eia.doe.gov/cneaf/alternate/page/environment/chap2.html
"Twenty-six million miles from Earth, in an orbit much closer to the Sun, Venus spins through space with a furnace-like surface temperature of more than 800o Fahrenheit (F) (426.5o Celsius [C]), which is much hotter than its proximity to the Sun would explain. Scientists used to believe that Venus fell victim to the greenhouse effect because 96 percent of its atmosphere is carbon dioxide, with nitrogen accounting for almost all the remainder [26]. It is now generally agreed within the planetary atmospheres community that carbon dioxide alone would lead to an average temperature of less than 25oC. The primary reason that Venus is warmer than this is the presence of sulfuric acid cloud cover over the entire planet, extending from about 50 kilometers to 70 kilometers from the surface."
3.2 Energy Balance
At a distance of 108.2 million km, Venus is closer to the Sun than the Earth by a factor of about Ö2, and so has about twice the incidence of solar energy. It is also much hotter at the surface, nearly 2 times more than the terrestrial mean of about 300 K. These facts are not simple to reconcile, however, because the ubiquitous and highly reflective cloud cover on Venus reflects 76% of the incoming solar flux and this results in a smaller net solar constant for Venus than for Earth. The high surface temperature must, therefore, be due to ‘greenhouse’ warming produced by the thick, cloudy atmosphere, possibly augmented by a contribution from the internal heat of the planet.
It is not simple to prove that the observed atmospheric conditions can in fact generate such a large ‘greenhouse’ effect. The problem is that the massive amounts of carbon dioxide are very effective at blocking the emission of thermal infrared radiation, but only at those wavelengths where the gas has absorption bands, which are far from covering the entire spectrum. Moderate amounts of water vapour are also required, and even then considerable spectral gaps or ‘windows’ remain. These could be blocked by the clouds, since liquid or solid absorbers present some opacity at every wavelength, the details depending on composition and particle size. The problem for early theorists was that using clouds to ‘close’ the greenhouse also tended to block the incoming sunlight, so that the calculated equilibrium temperature of the surface remained well below that observed.
This problem began to be resolved when it was realised that the clouds are made of sulphuric acid droplets, at least in the higher, most easily measured layers. These have the property of being highly absorbing at thermal infrared wavelengths, while being nearly conservative scatterers in the visible and near infrared. Thus, the clouds tend to diffuse downwards those of the incoming solar photon that they do not reflect to space, while blocking thermal emission from the lower atmosphere and surface. This explains the result, surprising at the time, that the Venera landers in the 1970s were able to photograph the surface in natural light. It also means that radiative transfer models, involving weak as well as strong bands of CO2 and H2O, plus those of the minor constituents CO, HCl and SO2, can account for the high surface temperatures by careful incorporation of the scattering and absorbing properties of the clouds.
The total solar energy diffusing through the cloud cover on Venus corresponds to about 17 watts per cm2 of surface insolation on the average, about 12% of the total absorbed by the planet and the atmosphere. The high opacity of the gaseous atmosphere and cloud at longer wavelengths requires the surface to reach temperatures high enough to melt zinc before the upwelling flux is intense enough, and at shorter wavelengths, so that equilibrium is attained. An airless body with the same albedo and at the same distance from the Sun as Venus would reach equilibrium for a mean surface temperature of only about 230 K. This 500K greenhouse enhancement of the surface temperature compares with only about 30K on Earth and 10K on Mars.