| 英文摘要: | Climate models have increased in complexity over time as more processes have been included. Now we need to return to the underpinning basics in the models and ensure they are the best they can be. All predictions and projections of weather and climate from days to centuries ahead fundamentally rely on models of the atmosphere, ocean and land, increasingly including representations of biological and chemical processes. Much of our scientific enquiry in climate science makes use of the same set of tools, which are collectively referred to as climate models. Lives and property are saved every day by the application of weather models, and climate model results underpin major planning decisions for our future. The use of models is very common well beyond the field of climate science. However, unbeknownst to many, climate models differ fundamentally from those used to predict the behaviour of many other systems, such as population or economic models. While the latter are often based on statistical relationships derived from the observed behaviour of the system, at the core of climate models are well-known fundamental laws that describe the circulation of the atmosphere and ocean complemented by complex sub-models of less well-understood and unresolved processes. Building climate models involves four fundamental steps: - Expressing the fundamental laws in mathematical terms1.
- Applying numerical approximations to the resulting set of equations2.
- Building and implementing sub-models — often referred to as parameterizations — for those processes that are excluded from the model equations, but are important. This includes processes that act on scales smaller than those represented by the numerical model grid and processes for which there are no straightforward equations or for which our understanding is incomplete, such as biological processes3.
- Assembling all components and adjusting model parameters to fulfil observed global constraints, often referred to as tuning4.
Over recent decades climate models have become increasingly complex by including an ever larger number of processes deemed potentially important to the climate system (Fig. 1). The community using climate models for its own scientific enquiry and for decision-making has grown dramatically, culminating in the establishment of climate services alongside the weather services in many countries5. Given this, it should be self-evident that building and improving such models should be one of the highest priorities in climate science. Is it?
This commentary is the result of many discussions with colleagues and friends. I'd like to thank all of them, none more so than Bjorn Stevens, Pier Siebesma and Sandrine Bony.
Affiliations
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Christian Jakob is at the Australian Research Council Centre of Excellence for Climate System Science; School of Earth, Atmosphere and Environment; Monash University, Wellington Road, Clayton, Victoria 3800, Australia
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