Do Nothing Case
The IPCC documentation gives us a pretty good insight to possible scenarios. While the models may not be totally accurate and some things will be wrong ( it is never possible to accurately predict the distant future), the IPCC documentation is a good starting point.
They tell us that average temperatures across the globe will increase by 2-6 degrees C and that sea level will rise by 0.2 – 0.6 m if there is no rapid collapse of ice sheets. Temperature increases in some particular areas (eg far northern latitudes) are likely to be greater and some areas less (eg southern Australia). Sea level rises are assuming a slow and steady increase in sea level from oceans heating (and expanding) and from glaciers slowly melting. It is likely there will also be some catastrophic ice events (Antarctic ice shelf collapse).
The northern hemisphere will feel the impact most. As previously discussed the Antarctic is more isolated and has been stable through higher historic CO2 concentrations. The northern hemisphere has greater landmasses, industry, population and crop emissions of GHGs.
Expected issues are droughts in mid latitudes (lower grain yields) with hundreds of millions of more people exposed to water stress, plant and animal extinctions, severe coral bleaching and mortality, more damaging tropical storms and flooding, severe coastal impacts and different patterns of disease (more widespread mosquito borne diseases).
These predictions are regularly updated and scenarios expanded. The 4-6 degrees of warming scenario becomes possible if CO2 levels in the atmosphere rise to about 1000 ppm or greater whereas the 2 degrees warming is more likely if we keep CO2 levels below about 500-530 ppm. Current levels are about 400 (with seasonal variation).
Post 2100 sea level will continue to rise putting many seaside settlements in jeopardy, pretty much whatever the CO2 scenario. Very high CO2 levels will ensure massive ice sheet losses and sea level rises in the tens of metres over the next centuries. This is similar to what the earth experienced at the end of the last ice age (about 8-12000 years ago).
Do everything case
What if we banned fossil fuels tomorrow, as called for by various groups? It’s probably impossible to force on the world population, but if we could, what would happen?
The immediate issue would be transport. Air and sea transport would be in trouble, isolating a place like Australia. We could probably keep a few planes going using biofuels and replace fuel oil propelled ships with sailing boats if we had some new materials. Fibreglass and plastics are made from hydrocarbons and would therefore be unavailable. Steel making requires coking coal, making this also unavailable.
Road transport would be severely reduced, as would mining and smelting as these require massive energy input. While we already have little manufacturing in Australia, this would reduce to almost zero, as there would be almost no raw materials.
Food production would drop almost immediately as we would have no fertiliser (currently manufactured from natural gas) and little transport or machinery. Small farming would take up some of the slack, but modern farming techniques have allowed the world population to be well fed. In the 1950s and 1960s one of the major world concerns was that we could not possibly produce enough food for 7 billion people and we would all be starving by the 21st Century.
Medical supplies would drop off quickly as the world became more local. Simple medical procedures would become impossible with people dying young of things like appendicitis.
Life would quickly become basic and a large portion of the current population would die off. Land would be stripped for resources (firewood etc) and CO2 levels would potentially rise in the short term. In the long term it would depend on whether humans could invent enough local technology quick enough!
So what do we do?
Doing nothing and banning fossil fuels are not ideal solutions, but various people support each of these possibilities? What we do mostly depends on politics and how much people feel the need to act. The world’s population, each have a different perspective and hence a different idea on what to do. Hence political solutions are the go.
We know we need to reduce the amount of GHGs we put into the atmosphere and equally we need to increase absorption (increase forests, burial etc). Politicians need to create systems where this can happen. Scientists need to supply ideas, methods and research and critically assess all of the new technology. Most of our current green technology requires massive amounts of mining and creates its own environmental destruction.
Solar, wind and associated battery backup require new raw materials including lithium, cobalt, nickel, graphite, manganese, neodymium etc in ever increasing amounts. Lithium batteries currently last about 1000 -1500 cycles (3-5 years) under ideal conditions (25 deg C) and must be regularly replaced. Large scale systems have a life of up to 6000 cycles. Recycling is possible but is energy intensive.
These new green technologies are part of the process, but are still a long way off being the answer. They also need base load backup at this stage. This should be managed in a way that is least polluting, particularly with regard to GHGs. Currently in Australia this is likely to be from a coal fired power station, which is one of the worst options. Natural gas is a much better (but not ideal) option.
As we have seen, each country has its own particular resources and issues. Each country needs to work through their best scenarios. There has been a lot of progress for electricity generation with nuclear, geothermal, hydro, solar thermal, wind all as potential sources. Each needs to be pursued and assessed by both scientists and politicians, and increased where possible (keeping economics firmly in mind). We need to markedly reduce the amount of coal burned or greatly improve our carbon capture techniques. Gas should be used instead of coal if other options are not viable.
Where we could get to low carbon emissions for electricity generation quite quickly (if we had the political will), transport, farming, mining and steel manufacture are in a different position. These still require fossil fuels to a large degree. I don’t know of any solar / battery options. Nuclear is, however a reasonable option and manufacturing hydrogen is also a possibility.
If I were to design a transport system from scratch for Australia, which used the least hydrocarbons (and not too concerned about cost) it would have to be based on a rail system. If electrified, it could be run on nuclear power (similar to France). Smaller scale electrified rail systems would also satisfy the transport needs of cities. Bitumen, trucks and cars would be kept to a minimum and the vehicles run on hydrogen.
Hydrogen can be produced from water with little environmental effect. It requires a large energy input (zero energy in water) to separate the hydrogen and oxygen molecules which can use solar, nuclear or whatever other input. It can also be managed from methane with a lot less energy but the CO2 would need to be dealt with.
On the large scale then, I think nuclear will be necessary to satisfy major transport energy needs. Solar and wind a good options for local and household needs (although heating and cooking are likely to require backup. Some degree of fossil fuel use will be with us for quite a while yet!
We need to keep farming efficient to keep fuel requirements low. Solar energy will help for farmers electricity needs but a liquid fuel will most likely be necessary for equipment and transport. Fertiliser use should be minimised where possible, but will most likely be manufactured from natural gas for the foreseeable future. The process need to be made efficient and non polluting.
Contrary to many published articles meat production is generally not a major issue, except for intense fattening procedures. Rice farming is more of a problem as it has a very large methane issue. In Australia, sheep and cattle roam on pasture land that is not really useful for much other farming. They eat grass and stubble that would otherwise grow, die and release as much methane / carbon dioxide as the animal does. Growing grain to feed animals is more of an issue. Recent published scientific papers have pushed these points.
As individuals the best we can do is to reduce our own energy use and waste. The hardest issues are things like travel (planes, boats, 4Wds all produce huge amounts of GHGs), heating and air conditioning. Fifty years ago electricity was about ten times the current cost (adjusted for inflation), but we used very little.
Today we expect fuel to be cheap so we can use as much as we like. I think we may need to reduce these expectations and return to significantly lower use!