Today we looked at variations in climate - or, the things that mean you can't just say "If we do X, then the temperature will go up by Y, and the future weather will be Z, A, B." Top tip : there are lots of them - some natural and some anthropogenic.
Some of the things that affect the global climate (and also local ones) include:
Volcanoes, sunspots, greenhouse gases in the atmosphere, aerosols in the atmosphere, cloud cover, land use changing albedo.
Then we have the things we know are feedbacks, ie they change due to changes caused by those things above and have further impacts on the climate:
Water vapour in the atmosphere (causes heating, which causes more water vapour to end up in the atmosphere); Ice albedo (reduces when ice melts, reducing reflectivity, increasing temperature); cloud feedback (which may or may not alter how much sun gets in and how much heat escapes - they don't actually know but they know it does something; the biosphere (things like photosynthesis of plankton and its 'eating' of carbon dioxide, reduction of forest causing increases albedo but decreased carbon dioxide uptake).
So, it's complicated. And known as a dynamic equilibrium. Insert stuff about the Gaia hypothesis and Daisyworld here.
And then we have stuff like the difference between the land and ocean heating rates from the same amount of sun, the earth's rotation creating weather patterns including global ones like trade winds and ocean currents like the thermohaline circulation - which, incidentally, will not create an ice age in two days if it stops. It might make Europe a bit colder. Um, where was I? That's right, variables. We have seasons, axial tilt, large land masses affecting currents and winds, and things like El Niño and La Niña - and I finally found out what causes them.
Incidentally, we're currently in La Niña, which in NZ is quite pleasant because it makes things a bit warmer and reduces the wind somewhat.
And there are other effects similar to those ones like decdal variabilities and annular modes - none of which have any net effect on global balance, but which do affect what weather we're having in any given year - thus, if the climate increases in temperature by 2 degrees and we get La Niña, it'll be still warmer, whereas if we get El Niño on top of that, it may cancel out the increase - but only for that year.
The upshot of all this is that it's really, really hard to predict what effects climate change will have, because there are so many variables and those variables produce feedbacks which create further variables, and on top of that we have variations that will exacerbate or cancel out the effects of our double-decker variable stack.
Lost yet? Well, the climate folks are trying to make exactly such projections using models. It's got a lot easier since the advent of computers. The history of climate modelling goes like this:
Mid 70s - the variables the models took into account were rain, CO2, and solar radiation.
Mid 80s - the model worlds got land, clouds and some ice.
1990 - they realised the worlds should have oceans, but only included them as static bodies of water.
1995 - added volcanic activity, sulphates, and circulation in the oceans.
2003 - added the carbon cycle, aerosols, rivers, and overturning circulation in the oceans (thermohaline).
2007 - models now include atmospheric chemistry (such as CFC effect on ozone and the repair of the ozone hole) and interactive vegetation.
And all the time, as processing power increases, the resolution of these models is improving. Also, if this stuff interests you, you can add your machine to a network and help run models at this site. Neat!
So the upshot of all that is that models to make projections for climate change have come a long way since climate change was first a thing. The models are now (in retrospect) able to pretty accurately predict rainfall, effects of volcanic activity, model water vapour feedback and global cooling, and project long term trends. The modelling hardware at NIWA is currently doing about 50 teraflops of projecting long term trends. It has to, with all those variables.
And in case you haven't been paying attention, these increasingly-accurate models are projecting a minimum of two degrees warming even if we reduce our emissions today. Two degrees? Not much eh? Have a look at what the increasingly accurate models are saying the impact of two degrees would be. And remember, they are now saying a minimum of two degrees. Meanwhile, 2010 was a record year for emissions, and 2011 is shaping up to be another.
So, um, do something* please. Like, now. And convince those around you to do something too - including voting with this as a major issue. Because if you don't, we are all fucked, essentially.
Finally, we lost Ben Hana yesterday. Ben was an institution in Wellington. He wasn't only a character who pretty much everyone recognised, he was a symbol of a city in which homelessness did not make one invisible. Tell me something, Wellingtonians - now Ben is gone do you know the names of any of the homeless people here any more? Because there's a bunch of them. I hope the outpouring of *dunno what to call it* for Ben doesn't lead to self-satisfied backpatting and ignoring the issues that he made plainer by his presence.
* I feel pretty justified in spitting on people who drive inessential SUVs to be honest. Those folks? Don't care if I die and they place their status above my survival. Fuck them.