Here is one of my first posts on the SDMB when I joined in 2002.
[ul]Seven years later, the graph of carbon dioxide concentration has continued its upward trend, such that it is now higher than at any point in the last million years, at least.
[li]Anyone who thinks this recent increase is natural, not human-caused, must explain why, amongst all the gentle undulations on this graph, the huge spike at the end just happened to coincide with the Industrial Revolution, where humans started digging up safely buried stores of carbon and burning them.[/li]
[li]The shape and vibrational characteristics of the CO2 molecule results in it absorbing infra-red wavelengths emitted by the Earth – a mechanism called the Greenhouse Effect, discovered nearly two centuries ago by Joseph Fourier. Most of the gas in the atmosphere does not do this (nitrogen and oxygen absorb and scatter blue wavelengths, hence the colour of the sky), which is why increased CO2 concentration is a significant change to the atmosphere even though it comprises only a tiny percentage of it. If all of the CO2 were removed from the atmosphere, the Earth would be a much colder place.[/ul][/li]
I propose that all of the above is undeniable outside of an utterly unhinged Young Earth Creationist mindset.
Now, you might argue, as many Anthropogenic Global Warming deniers do, that the correlation between this CO2 increase and the overall temperature increase is entirely coincidental (or deny any temperature increase at all by saying “Hey, 1998 was the hottest year on record so we’re cooling now, right?” :rolleyes:). In this debate I wish to wipe the slate clean of all such bickering over correlations past and present (and yes, I understand that the natural changes in the past were different to what’s happening now in all kinds of ways). Instead, I wish to concentrate solely on predictions for the future.
What is your personal prediction for:
[ul]A) The shape of the CO2 concentration graph. Do you think it will level out? If so, at what level? (For info, the level stayed roughly constant at 280 ppmv for millennia before the Industrial Revolution)
[li] B) The consequences of the level you guessed for A). For example, if we burned literally *all* the carbon stores we have access to, the level would rise above 800 ppmv = *three times* the historical average. Does anyone think that such a level would have *no* significant consequences?[/ul][/li]
Your guesses may be as vague and hand-wavy as you like, especially for B). Note that for A), however, you might well have to explain why you think the graph will not continue its upward trend given that humans are still burning carbon stores at a similar (and perhaps even an increasing) rate.
Personally, I’m a pessimist who would love, repeat love to be proven wrong:
A) 600 ppmv. A level-off at 450 ppmv or so would have required Kyoto to be much more ambitious and universally adopted. The next protocol would have to be far more ambitious still. I think we had a chance back in 2002, now I think we’re locked in to whatever will come to pass.
B) A subsequent, time-lagged temperature rise of over 2[sup]o[/sup]C and a longer-lagged sea level rise of over a metre. In industrialised democracies, this might not be too bad – maybe a few more New Orleans here and there. But in places like the world’s 7th most populous country, 50% of which is 1m or less above sea level, tens of millions of climate refugees will be forced into its neighbours’ territory, all of which have nukes. The news will get interesting. I believe we live in a golden age of being to swan around a largely peaceful world for a few hundred dollars a time, in a way our grandchildren might envy us for.
As a side bet, I offer that the world will see a new hottest-ever temperature record within the next 7 years, with the loser agreeing to post a photo on the SDMB holding a placard whose climate-themed and swear-free wording is chosen by the winner.
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