Registered On: September 7, 2015
Yeah, climate change has happened previously and I don’t think there’s one person who disagrees, barring creationists. The difference is that past instances can be linked to natural causes. The current natural trend is that of a slight cooling. We aren’t seeing that. Instances of past hot climates (such as during the Carboniferous) can include that of a weaker Sun, but with high greenhouse gas levels (take note, those who think the Sun is the only factor necessary to explain climate change). Of course volcanoes would be the source of past greenhouse gas initiated climate change, but that doesn’t seem to be the case now. We know greenhouse gases can affect climate and have done since the 19th century, we know that climate is warming, we know that the only variable linked to an increase is that of CO2 and we know that the CO2 input is predominantly from human sources, so we have a solid idea that humans are responsible.
It wouldn’t be the first time life has had such an influence. The evolution of plants led to a huge decrease in CO2 levels back in the Devonian. This was followed by global cooling and a mass extinction event of life adapted to hotter conditions at the time.