The short answer, Newtonian is no. The Sun is not heating up. But rather it's growing more luminous on a daily basis, albeit a tiny amount on less than epochal scales.<br /><br />Global warming is a combination of phenomena. Yes, greenhouse gases are on the rise. But perhaps more detrimental is that as the polar ice caps melt, more water vapor is introduced into the atmosphere and the Earth's albedo (thus it's reflective capabilities) is decreasing. A double whammy, if you will.<br /><br />As far as the Earth becoming like Venus goes, we have that wonderful 24 hour rotational feature going for us. At least <b>our</b> atmosphere is alternately heated and cooled on a 12 hour basis.<br /><br />I've read some stuff on global warming relative to CO2, but one thing I've never seen taken into consideration is that as sub polar and polar areas thaw, reforestation would occur. More trees to process CO2 in other words.<br /><br />Rampant deforestation, however, could tip the scales and negate any beneficial effects of polar reforestation, I'd think.<br /><br />Without doubt, CO2 emissions can magnify the greenhouse effect. But 90 million years ago, sub arctic latitudes were sub tropical ones. Earth was a much warmer place. But to temper that statement, there were a lot more trees then, too, I would have to imagine.<br /><br />As far as comets plunging into the sun to enhance its mass, I'd have to discount that idea, and I'll tell you why. It's all about scale.<br /><br />Relative to the Sun, no comet we know of has anything remotely approaching significant mass. There's a million degree buffer zone between the surface of the Sun and any incoming comet.<br /><br />I'd have to guess that not only would any comet be vaporized essentially instantly but that the momentum of individual Hydrogen and Oxygen atoms would be negated before they could add to the Sun's mass.<br /><br />Sorry to digress, but I saw some comments that interested me, and I don't often get to pipe in with pertinent information. <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>