Why do we get a range of results?
Our future climate depends crucially on how much greenhouse gas we emit. Emissions, in turn, depend on trends in economic growth, global population, and technological change.
For this reason, a range of scenarios (developed by the IPCC) are used which paint different pictures of the future. The graph below shows NIWA’s full range of projections for New Zealand’s annual average temperature by 2090.
These results are based on 12 climate models across six emissions scenarios. Each asterisk shows an individual climate model result. The bars show the full range of results for each emissions scenario.
This demonstrates that different climate models give different results, although many ‘cluster’ together. The scenarios have been ordered left to right from lowest greenhouse gas emissions (B1) to highest emissions (A1F1). Clearly, the scenarios with higher greenhouse gas emissions will likely result in greater increases in temperature by the year 2090.