Global warming is caused by a whole host of gases and particles. In addition to the chief villain – carbon dioxide from fossil fuel use – two of the most important are methane and nitrous oxide, both of which are generated in large quantities by agriculture and fossil fuel extraction, among other sources. Then there are all the refrigerant gases used in the world's air conditioners, fridges and freezers; the soot generated by cars, industrial plants and cooking fires the world over; and even the vapour trails left by in the sky by aircraft.

With so many warming agents at work, companies and governments are often faced with complex and even controversial decisions about which ones to prioritise. The debate stems from the fact that the various gases and particles operate at very different timescales. Carbon dioxide, nitrous oxide and some refrigerants stay in the air for centuries or even millennia, locking in warming for all the time they are there. The others – collectively know as short-lived climate pollutants or SLCPs – create a burst of warming that is powerful but brief. Soot's impact is gone within a few weeks. Methane stays in the air for an average of around 12 years (confusingly, it then becomes CO2) and hydroflurocarbons, used in refrigeration and insulation foam, typically last around 15 years.

Fresh water is crucial to human society – not just for drinking, but also for farming, washing and many other activities. It is expected to become increasingly scarce in the future, and this is partly due to climate change.

Understanding the problem of fresh water scarcity begins by considering the distribution of water on the planet. Approximately 98% of our water is salty and only 2% is fresh. Of that 2%, almost 70% is snow and ice, 30% is groundwater, less than 0.5% is surface water (lakes, rivers, etc) and less than 0.05% is in the atmosphere. Climate change has several effects on these proportions on a global scale. The main one is that warming causes polar ice to melt into the sea, which turns fresh water into sea water, although this has little direct effect on water supply.

As the water passes its height and ebbs away from St Asaph, Ruthin and York, we look on with sympathy. This time round we had only minor puddles in our bedroom from water oozing through the stone walls. Back in July, the whole ground floor of our converted riverside barn was feet deep in black river water and devastated. The worst time, I now appreciate, is not when the water is swirling past your windows and gushing under your doors. While that's going on you have too much to do to panic or feel sorry for yourself – carrying stuff to safety, rescuing the cats and chickens, checking on neighbours – and everyone else wants to help. The misery comes later, when the rest of the world seems to be back to normal: the news no longer shouts "Floods devastate England and Wales", and yet your home is a wreck.

Outside lie enormous heaps of sodden possessions, not just beds and carpets that can be replaced, but once-loved books, old clothes, photographs and paintings that cannot. These stinking heaps do not instantly disappear but remain as a reminder of all you've lost until the insurers give the go-ahead. Then begin the phone calls and emails to loss adjusters, builders, engineers; the forms and databases of every item lost, with estimates, receipts and even photographic evidence to prove that you really did have that little wooden summer house that was completely swept away in the torrent.

Wealthy countries have not only failed to provide cash to help poor people adapt to climate change, but much of what they have agreed to give so far has come out of existing aid budgets or in the form of loans that will need to be repaid, new research by two international agencies shows.

The EU and nine countries including the US, Canada and Australia agreed at the Copenhagen climate talks in 2009 to make a downpayment of $30bn (£18.7bn) by the end of this year on the eventual $100bn that must be raised by 2020.

But separate analysis by Oxfam and the International Institute for Environment and Development (IIED), shows only $23.6bn, or 78%, has been committed and much of that is not "new and additional" to existing aid, as was agreed.