Refractory |
Climate changeWe've been about 12000 years in a warm period, that's a period in which agriculture was first developed. Cities, towns, civilizations and so on. That cycling between ice ages and warm periods is paced by the earths orbit around the sun. But the actual change in sunlight that comes in is very small compared to the big swings between ice ages and warm periods. Two things draw into those swings, one is green house gases, of which carbon dioxide is the most important, and the second is the ice ages waxing and waning. We are in a long warm period of very stable climate so we would not expect to see any appreciable change in climate over the next 10,000 years in the future. Just as nature sometimes puts more greenhouse gases into the atmosphere, the earth warms. If humans do the same thing, it's a no brainer — the earth will warm. And that's exactly what we see. So what we're now doing is moving above that very long stable period of climate that we expect to last for about twenty or thirty thousand years. And we know the cause very very well, this cause that we see now is not natural variability, we know very well the various types of natural variability and what we're seeing now is a response to the additional greenhouse gases that have come into the atmosphere after the industrial revolution. The scientific community is more than 90% sure that what we're seeing is not a natural swing in climate. That's about as close to a consensus that you'll ever get in the scientific community. So there is basically no doubt in the scientific community.
The whole aim of reducing greenhouse gas emissions by whatever economic instruments or other regulatory measures you take is to actually take that pressure back off the natural climate system that we're putting on through the additional greenhouse gasses, so that we in fact don't have to manage the climate, we can let nature manage the climate as it always has. So there is a big philosophical and ethical and scientific difference between letting the emissions go and then somehow trying to manage the climate, OR taking the pressure back off the climate.
The situation:
We're sitting at about 0.8 degrees Celsius above pre-industrial level now, that's a global average. There is a lot of momentum in the system mainly stored in the ocean. If we could cut emissions to zero tomorrow (which we can't) and let the climate slowly come to equilibrium, we'll get about another 0.4 of a degree so we're sitting at about 1.2 guaranteed. We think that anything above 2 degrees will put us in some reasonable dangerous territory, and some scientists argue that 1.5 is a better number. this puts a real sense of urgency in getting these emissions down. if we don't, if we continue on the trajectory we're on now, a good bet is somewhere around 4 degrees late this century, with a range of a best case of maybe 2.5 and a worst of 6 degrees above pre-industrial.
at +4, you'll get massive heatwaves. Lets take for example the heatwave of Melbourne in Feb. 2009. This was a mega event, it was over 3 degrees above the previous high temperature max heatwave. This is unheard of when you look at climate records. Then there's the heatwave in Russia, heatwave in EU in 2003. If we keep going towards a 4 degree world, by the mid century that will be an every day summer event. At 4 degrees average temp rise say by 2080, that event in Melbourne will be a cool summer day. This is what it means in terms of how extremes change. They change far more than averages.
The difference between ice age and warm period is just 5 degreesTo give you another indicator, when we swing from an ice age to a warm period, where in an ice age, most of the northern hemisphere is under ice - that temperature swing is only about 5 degrees in average temperature. So we're headed for very close to the same magnitude as between an ice age and a warm period. Don't be fooled by thinking that going from 24 to 28 is not a big change, it's a huge change in terms of how the climate system operates.
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