The theories are not easily explained. This doesn't prove your point though. Simply because you don't understand the science or because you're not able to comprehend it doesn't mean it's not right. You're probably right in saying that there're conflicting studies from the past, but as time goes on new evidence and technologies come about.
I can explain some parts of the theories you mentioned, but that's pretty much as far as my current knowledge goes as this isn't really my field. I will try however, because I find this rather interesting.
1) Determining the climate from long ago is done by looking at the vegetation and other signs in the earth's layers, there's a lot to it that I don't have all the knowledge of. I don't know if it's true that it's currently more than ever before (doubt it), I think it's about the current rise being more than you would expect from the interglacial we're in (so compared to measurements from the last few thousand years instead of millions, a 4,5-billion-year-old earth has gone through a lot I'd imagine).
2) Then of course an important piece to the puzzle is the correlation between the rise in temperature and the CO2 levels in the atmosphere. I'm aware of the skepticism surrounding the evidence found in the ice cores and I know there's also an answer to that. Like the other facts mentioned here, there's much more to it than I currently understand since I'm not a scientist and didn't specifically study this topic. I'd say it's still solid science that could be disproven, or whatever it is you're looking for exactly.
3) I believe isotopic signature is the main way of telling which CO2 comes from volcanic activity and which is from human activity. The amount measured for human activity actually tallies with the known amount of CO2 production. This told us for example that the volcanic activity accounts for 500 million tons of CO2 which is not even 2% of the 30 billion tons from human activity per year.
4) There's a lot of reason to believe we do know how it works, however complicated it is. The Green House effect is a real and measurable thing that relies on, mainly, the amount of CO2 in the atmosphere to provide with a certain level of trapped radiation from the sun. No Green House effect means the earth will be one big snowball, to much of it and the temperatures rise significantly. There's the axis of the earth which changes as the course of the planets in our solar system changes over millions of years, positive feedback loops like the albedo effect, ocean currents, natural breathing of the earth between plants growing and dying every year, etcetera.
5) The ever increasing world population is the main problem we have, that's not only about climate change but also about the bio-capacity of the earth which makes it unsustainable. We're burning fossil fuels which we will soon run out of, making renewable energy the only option (and soon the cheapest). If every country sets their minds to living in a sustainable way, it is possible to massively reduce our emissions. Combined with the actual effect of climate change that we should all want to avoid, I'd say there's enough motivation and we're in the middle of a huge transition (that will take some time of course).
You’ve not answered my questions Sunapple. I asked what you would accept as proof that each of these theories are false. If you cannot accept anything as proof of a theory being false, then either the theory itself is not scientific (because falsifiability is a precondition of a scientific theory), or you do not understand it, and are merely dogmatically repeating what others say.
But let's go through them anyway...
1) Many scientists have been taking core/vegetation samples and trying to build tables of data. But that's just data. Data itself doesn't draw its own conclusions. Humans do that.
Ever worked in business where you were preparing slide shows for corporate shareholder meetings? I have. It's amazing how much the "official" numbers can be played with. Give the accounting and executive teams 4 hours, and you'll see four VERY different pictures of the company's financial health emerge... All of which are technically "true". It's all about massaging the data to fit a narrative.
Given the polarization of "Climate Change" by the true believers, and the financial rewards involved for towing the party line, I can't imagine that there would be any less playing with the numbers than I saw with the fortune 500 companies that I once worked for.
I once read a report on continental subduction from a science station in South America. In an otherwise boring paragraph near the end, they noted that the measured movement vectors had been "inverted" during the study. Inverted! Do you know that that means? A vector is a mathematical representation of motion. If they inverted their measurements, then it means that the fault they were studying wasn't subducting. It was diverging.
That would be heresy to the established theories of plate tectonics for that region, but guess what? It would fall in line with recent US Navy data that seafloor samples collected closer to that fault were geologically newer than those collected further away. So their data was being played with to fit an accepted "scientific" narrative, and plate tectonics doesn't have anywhere near the level of political or monetary interest as "Climate Change."
Answer: No, the climate is not changing faster than it ever has before. For proof of that, simply consider the wooly mammoths in Siberia that were somehow flash-frozen in the middle of eating lush grass. They were preserved so well that WWII prisoners in Siberia were able to eat their meat when they found them under the permafrost.
What does that, I wonder? The sun turning off for a few minutes? Some rogue celestial body getting between us and the sun? A polar shift? Alien teenagers on bender? Dunno. But it should give pause to anyone who thinks they know everything there is to know about the world's climate.
2) Again... You don't know.
So... What about the levels of methane in the atmosphere over time? You do know that methane traps the sun's heat at 84 TIMES the rate of carbon dioxide, right?
Is anyone measuring that? No, since "Carbon" is the apocalypse buzzword that gets studies funded, and methane is extracted, distributed, and politically protected by big businesses. But it leaks out of every oil well, especially those that are "fracked". It also leaks out of every system of gas piping to residential homes. If man IS warming the planet, then methane will be doing at least as much of the work as carbon dioxide.
Have you even heard of the solar cycle? The eleven year period where the sun's heat output waxes and wains by a small, but significant amount? They're correlated to levels of sun-spot activity, and sun-spots are believed to be "holes" in the sun's corona created by magnetic fields. But magnetic fields require electric currents to form, and both electricity and magnetism have been completely ignored in cosmology for over a century now. So we actually know jack-all about how the sun actually works, and can't expect it to any more steady-state than the earth.
You probably also don't know about the "Little Ice Age" that Europe suffered from 1645 to 1715. Which just so happened to coincide with a solar event called the "Maunder Minimum". When sunspots were extremely rare.
3) Again... You're only looking for carbon dioxide sources. While ignoring solar activity, and the role of methane.
4) Thank you for the elementary school story of global warming. Based, as it is, on looking at Venus, and assuming that it was once Earth-like (which we have no rational basis to believe).
Again, you don't know all of the potential warming factors. Nor, evidently, have you ever worked with computer simulations. Which are only as accurate as the data you feed into them. Don't like the result? Then you trial-and-error your way to the result you want.
But tell me... If we DO know pretty much everything about the Earth's climate... Then why are weather forecasts still so inaccurate? Seems like those expert computer models should be able to give us 99% weather accuracy out to at least a decade if we're going to make compulsory, life-altering decisions based on them. No?
5) The problem isn't overpopulation, so much as how much of that population is unproductive.
There is NO sustainable level of human population that wouldn't see us reduced to the technological and social level of the middle ages. And then we'd just be waiting for a bad ice age, or a large meteor, to wipe us out.
The technological civilization that we enjoy, and which will be the only thing that spreads us to other planets in this solar system, requires a large population. Why? Because we need people to specialize in particular technologies and their sub-branches. A society of subsistence farmers has no way of supporting an expert in rocket engine fuel pump fittings. Or microchip architecture. So for our species to spread, we need a productive society of people specialized in what they do.
What we don't need is people who are being paid not to work.
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Global warming and climate change is a fact. The only people disputing this are Mr. Pruitt (who never should have been put in charge of the EPA), Trump and his followers. Companies are polluting the water with chemical dumping, they are pumping green houses gases into the atmosphere, the arctic and antarctic ice shelfs are melting and raising the sea to flood land currently at or below sea level.... these are things we can see happening and we know the cause.
The real issue is, why do you put Scott Pruitt in charge of the EPA, when on his very own LinkedIn page, Pruitt describes himself as “a leading advocate against the EPA’s activist agenda.” His (and the President's) agenda is obvious. Pad the pockets of large companies by any means necessary. While this doesn't effect Apple's own operations, it is good to see companies like Apple fighting against a man that cares nothing for the environment. I applaud them for doing everything in their power to stop Pruitt and Trump from turning the US into a toxic waste zone.
People who jump into political rants after declaring something a "fact" do no service to their cause. Trump being an idiot politician is not an argument for, or against a real, testable scientific theory.