It's true that fluctuations exist, and we've had ice ages and warm periods in the past... Warm to the point where we had no ice at the poles. This has been linked to greenhouse gases, the Earth's precession, and solar cycles. According to patterns seen in our geologic history, however, there is no evidence that we
should be entering such a period now.
CO2 does cause global warming (whether natural or not). It's a definite greenhouse gas, and something we're pumping into the atmosphere all the time. The levels of CO2 in the atmosphere have been increasing steadily in the atmosphere at levels believed to be exponential. There is
no doubt that we're contributing a lot to that... All the junk being pumped out of cars, factories, and for other uses all has to go somewhere.
So while it's true that natural processes
may be involved, there is no evidence that I know of for them to actually be doing this now.
Something has to be causing it. Whether or not we are entirely at fault, we
are pumping junk into the atmosphere that is almost positively making things worse... With the levels we're dealing with, potentially much worse.
It will cost money to do something about it, but it will cost a lot more when things get out of control.
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Could global warming be turned back? Even if there's more to it than us, indeed I think it can. I won't go on about reducing our CO2 output as I'm sure we're tired of hearing, but what if we could suck the CO2 out of the atmosphere and turn it into something useful?