Aryeh Gregor wrote:
In contrast, by emitting carbon dioxide, you're contributing to an effect that won't be a big deal for at least a few more decades.
It's a big deal already, and by the time it becomes an even bigger deal, it will be too late to act. The global climate takes decades to respond to changes in forcing factors. Even if we stopped all greenhouse gas emissions now, the earth would continue to warm for decades because the heat capacity of the ocean slows down the lower atmosphere's response to increased radiation.
And that will probably become no big deal again a few decades after that when everyone's adapted to it.
Increased temperatures will cause a drop in rainfall and thus a reduction in food generating capacity in Australia, the Mediterranean, Mexico, and north-west and south-west Africa. High temperatures also damage crops directly. In the no-mitigation case, the Garnaut Review (which I've recently been reading and linked to earlier) projects a loss of half of Australia's agricultural capacity by around 2050.
Also in Australia, species will be lost as cooler mountain habitats disappear from the continent, the Great Barrier Reef will be destroyed, and significant freshwater coastal wetlands will be inundated by the sea.
And that won't directly kill anyone in any event, mainly just cause economic harm.
The World Health Organisation disagrees:
http://www.who.int/mediacentre/factsheets/fs266/en/ http://whqlibdoc.who.int/publications/2007/9789241595674_eng.pdf
You just sound gullible when you recycle such claims without showing any awareness the opposing viewpoint.
And that might not happen anyway if some clever soul comes up with a good enough fossil fuel replacement at any point in the next thirty years.
Like what? Nuclear fusion? Talk about pie in the sky.
Or if it becomes economical to pump greenhouse gases out of the atmosphere.
The Garnaut Review suggests that it may well become economical in a few decades, but only because mandatory targets will raise the price of carbon to several times its current value. This will happen when cheaper measures, like shutting down fossil fuel power stations, are exhausted. Economical doesn't mean cheap.
Or if some cheap scheme is devised to reduce warming some other way, like releasing particles to block sunlight.
And cause famine due to a reduction in tropical rainfall?
Or if some unforeseen negative feedback causes warming to not get too bad after all.
The other side of that probability distribution, of course, is that positive feedback will cause it to be even worse than the high-end IPCC predictions and that the sea level will rise by tens of metres. There are studies on which of these two outcomes is more likely. Some of us do not want to roll the dice.
And of course maybe we've already hit a critical threshold and cutting emissions is pointless by now.
There isn't such a threshold. The more you emit, the hotter it gets. As the temperature rises, the outcomes for both humans and for biodiversity become steadily worse.
Plus you can add the fact that Wikimedia's contribution to the affair isn't likely to be even measurable, especially if the major damage is from catastrophic changes (e.g., ice caps melting) rather than incremental ones. How much money do you owe for increasing mean global temperature by a billionth of a degree fifty years from now?
The cost per capita can be derived from the total cost using a complex mathematical process known as "division". Maybe you've heard of it?
-- Tim Starling