Future of our climate: Cloud research points to hotter, drier New Zealand

Studies of the way clouds form have changed the picture for climate scientists.

* New research into cloud processes shows that our climate is more sensitive to carbon dioxide than previously recognised.

* When the correct cloud processes are factored in, it is estimated that global average temperatures will rise by at least 4C by 2100 and probably more. This is an increase in temperature of 3.2C in just 90 years compared to an increase of 0.8C over the past 100 years.

* If we continue to produce emissions under a business-as-usual scenario, we will see temperature increases of close to 10C by 2200.

What it will mean for NZ

The two models of four degrees of global warming by 2100 produced increases of 4.4C and 3.1C over New Zealand.

* Rainfall would increase in the west and decrease in the east, and summer would bring a marked drying everywhere.

* Most lowland areas of New Zealand will become frost-free, climate scientist Dr Jim Salinger says.

* One-in-100-year rainfall events will increase by 32 per cent everywhere - which means increases of 50 to 150mm.

* For non-irrigated pastures, winter pasture will increase, but summer pasture growth will decrease because of lower soil moisture.

* For beef-sheep and dairying, the two models give a 3 per cent and 13 per cent, respectively, decline in beef-sheep production, and +4 per cent and -3 per cent change in dairy production.

* For pine forest, increased carbon dioxide gives CO2 fertilisation - the result is a 30 to 40 per cent increase in productivity, with productivity doubling in eucalypt forests.

Eight degrees of warming by 2200 would bring much more extreme changes:

* Christchurch mean temperature will be 20C, with frequent days piercing into the mid 40s.

* A sea level rise of 2.5m to 3m by 2200 will result in serious flooding and inundation issues for most of New Zealand's cities and towns.

* Glacial snow lines will rise 1200m from 1800m now to 3000m, which means New Zealand will have no mountain glacier cover left.

* The climate of Auckland will become tropical with a mean around 23C - equal that of central to northern Queensland, or Tonga.