Rossby Centre is working with both regional and global model development and also with the development of more detailed future scenarios, climate indexes and to quantify the uncertainties in climate scenarios.
More detailed future scenarios
Developments in regional climate modelling have progressed quickly over the past few years. A significant improvement in computer capacity provides us with the possibility of producing more detailed information in future scenarios for climate models. From previous calculations with a resolution of 50 km and shorter periods, it is now possible with a 10-25 km resolution and longer periods. And in a few years time, a resolution of 2-3 km will become reality. This development means that the amount of output data from a climate model will increase drastically.
How do you make climate data useful?
One way of communicating the complex issue regarding the effects of future climate change is to use a climate index. In discussions with users in different sectors, Rossby Centre is working with the development of different indexes based on the user’s needs which are in turn based on calculations from different regional climate models. The climate index is formulated from a user perspective and can for example describe complex relationships which include threshold values or exposure times for different conditions.
An important consideration is user friendliness and an understanding of the information the user has at hand, i.e. how methods are developed to present climate data in a good way so that the information is suitable.
There are uncertainties with future climate change. At the same time they present a difficulty for society as decisions must be made. One way of studying uncertainties in today’s climate models is the example to carry out calculations based on the same emissions scenario but with several climate models, or with boundary data from one and the same global model but with different emissions scenarios. The spread among the different climate predictions can be regarded as a measure of the present uncertainty as to how climate change works and how it is described in the models. This “ensemble” of simulations is used to better quantify uncertainty in possible future climate change situations.
The climate system's natural variability
In addition to anthropogenic factors on climate change, the climate system has a natural variability. These natural fluctuations from one year to the next, or from one decade to the next, exacerbate the analysis of projected climate scenarios. This is particularly true when you study climate change on shorter timescales. By the year 2100, the changes to the climate are expected to be so considerable that the trend will be clear even if the values vary heavily from year to year.
The natural changes in the climate system mean that when making forecasts of what the climate will be like in a few decades, the initial condition in the model calculations will play a more important role than when studying climate change from a longer time perspective, for example in 100 years. This means in practice that natural variations (which with today’s knowledge cannot be predicted) in the short term can either counteract or strengthen the overall trend which is caused by human emissions of greenhouse gases.