It's less than a week to Copenhagen. On Monday evening I heard Douglas Alexander, minister for International Development, say how important it is to get a deal and how hard the UK government will be working. I'd like to believe it. And it MIGHT happen. That is, we might get a deal that will reduce greenhouse gas emissions by enough to keep the temperature increase below two degrees.
But we also might not. In business and war it's always wise to have a backup plan in case your main plan doesn't work. So what should be in the UK's plan B?
We'll need Plan B if we can't keep the temperature rise below two degrees. The Plan B world will be defined by rising temperatures and sea levels, more extreme weather events and more refugees, both nationally and internationally. These effects will continue for several, perhaps many, decades with no certainty about the end point.
With more storms, tornados, etc., we can expect more floods and other damaging events.
Plan B should include higher standards for buildings and more investment in flood defences. New building on vulnerable land should be forbidden and some existing buildings will have to be strengthened or abandoned. We will also need extra investment in warning systems and the emergency services.
The cost of disasters will rise despite these measures and insurance premiums will rise in anticipation. The government will need to ensure that we have the right balance between prevention and compensation.
We are already abandoning some coastal land to the sea. This will happen increasingly fast in Plan B with obvious impacts on housing and agriculture. There may be some gains on high ground and in northern England and Scotland but the net effect will be negative.
All land use will have to become more intensive. In China, where land hunger is a permanent feature, almost everyone lives in tower blocks. We'll need to go in that direction, reserving all agricultural land for agriculture. The planning system will have to become more restrictive and, probably, more directive. Wasteful use of land must become first socially disapproved and then illegal.
The world will progressively lose agricultural land so the price of imported food will rise. The UK will therefore have to become more self-sufficient in food whilst using less fossil fuel for agriculture.
Plan B for agriculture will require a switch away from meat production to make more efficient use of the land and more intensive arable farming. New crop varieties will be needed to make best use of the new growing conditions and genetic engineering will be an essential tool if we are to do this in time.
If Copenhagen fails then there won't be a much point in cutting UK carbon emissions. However, energy security will be a big issue as climate change destabilises many of the areas from which we import oil and gas.
The keys to keeping the lights on in an increasingly unstable world will be demand reduction, diversity of energy sources and increased fuel reserves. Plan B will reduce demand by subsidising better building insulation, improving public transport and discouraging flights and driving. Much the same as Plan A in fact.
Plan B will also include a shift to sustainable forms of energy generation. Increased use of wind and tide will reduce our oil and gas imports. To provide diversity nuclear power will have a place, if we can secure access to Uranium, and it may be worth considering re-opening some coal mines.
At best the UK will struggle to feed its people. Since most of the world will be worse affected than the UK the number of people trying to come here will continue to increase. If we cannot feed our current population we can hardly admit significant numbers of new residents. Therefore we won't.
Plan B will require much stricter immigration controls which must, in time, apply to EU citizens. Since that is contrary to EU principles Plan B requires us to at least consider withdrawl from the EU. Plan B will also require strengthening of border controls and a generally tougher attitude to would-be immigrants.
But that won't be enough. It will become apparent, over time, that we cannot feed our existing population.
Plan B will therefore involve measures to reduce the population. It's unlikely that emmigration can contribute much to this so we need to concentrate on the birth rate. Forward planning will allow us to do this by voluntary means if we do it soon enough. If not, compulsion may be necesary.
Each of the policies I've discussed so far implies a reduction in traditional liberties. Several will create conflict with minority communities which will increase the need for social control.
Plan B will include strengthening of the internal security apparatus. Our record over the last 20 years suggests that too much control will be a greater threat than too little. Plan B should therefore set out the liberties that can be maintained as well as those that cannot.
The biggest remaining uncertainty from a planing perspective is the pace of change. Today's IPCC projections show gradual worsening over many decades. Given foresight and determination it ought to be possible for the UK to implement Plan B.
However, several lines of evidence show that the climate could shift very much faster than that, in years rather than decades. Planning for this is probably pointless since there is no precedent for change on this scale since the death of the dinosaurs 65 muillion years ago. The human species will doubtless survive - we are very adaptable - but few human institutions would be likely to.