We have no other way than science to find out how things work
As a scientist myself (well, I mostly do business today, but my background is science), I completely agree with you that the scientific method is the way to figure things out.
When it comes to global warming i only know that when NASA, ESA and their counterparts in a lot of other countries says that Global warming caused by human activity is real then i cannot dispute it unless i can back it up with some really good evidence, and since i cannot do that i just have to assume that they know what they are talking about.
It doesn't sound unreasonable that more CO2 in the air would increase temperatures. However, it also isn't unreasonable to very skeptical of climate models. Much of my scientific background is physics, scientific modelling, and financial modelling. Models that contain a multitude of adjustable parameters can be made to fit historical data very well yet be horrible at predicting future results. I am highly skeptical of complicated models of complicated systems.
The other things that raise my level of skepticism:
-- I remember the dire warnings about acid rain.
-- When I see a group-think dynamic with suppression of dissent, or science that transmutes nearly into a religious crusade, I become suspicious. Global warming has that in spades.
-- Few consider that the earth went through periods of much greater atmospheric CO2 than we have now or are extrapolated to have, yet life flourished during those times.
-- Few consider that dire consequences of warming are model predictions, yet periodic ice ages are much-more-solidly known to have occurred many times throughout history. An ice age would be drastically more ruinous to human civilization than warming. Might it be that some warming can delay, offset, or eliminate the next ice age, in which case it would actually be a savior of mankind? It might be as plausible as the dire predictions of bad aspects of warming.
We can hope for the best but we still have to plan for the worst..
You can't often operate by planning for the worst. If you planned for the worst in all things, you would not drive a car, have children, have pets, meet friends, drink beer, eat pizza, swim, play a sport, go out in the sun, etc. There is a potentially gigantic opportunity cost to operating as if the worst is going to happen.
Put another way, you've got $3 trillion to spend. Which of these is best for mankind?
1. Spend it on reducing CO2 emissions faster than would otherwise happen through unforced adoption of non-CO2-producing power sources.
2. Spend it on a way to preclude an ice age (as ice ages have wiped out lots of life in the past).
3. Spend it on asteroid defense for the planet (as asteroids have wiped out life a few times).
4. Let free markets spend it (and get advancement of various things, some you might consider not useful, but some definitely will be in healthcare, computers, food production, entertainment, science, increased standard of living for the undeveloped world, etc.).
5. Give it to your pal Brooke, who will put it to excellent use for the betterment of mankind.
6. Spend it on human colonization of space (to protect our species and spread sentient life).
7. The large number of other possibilities.
I like #5 most, with #6 a close second, and #4 third.