Are We Getting Better At Predicting Future Climate?

30 Aug, 2021 Article 7

By Collins Ochieng Onyaga

With contributions from the ICPAC Climate Change Technical Working Group

The Earth’s climate has changed a lot over the past billion years and at the moment, human influence on the climate system is now an established fact[1]. However, we should be talking about the future climate as well. This is important in planning and preparing for the adverse conditions ahead or doing away with the activities that are likely to contribute significantly to the problem. The past climatic conditions leave physical records that can be studied like ice cores and tree rings. Therefore the methods for reconstructing the past climatic conditions are different from the methods for predicting the future climatic conditions which are too abstract. However, there have been calls for the research community to pay attention to the past and actively involve it in predicting the future; arguing that if one can simulate past climates accurately, then the predicted future scenarios will be more accurate [2].

Climatic conditions are more abstract than historical conditions and are therefore projected using computer models.

These are mathematical reconstructions of the atmosphere accounting for as many details as possible to produce an accurate simulation of the future climatic conditions.

How far have we come

It has taken decades to build the models to a point where we can be confident that they are accurate. Global climate models grew out of the early computerized attempts to model the planets’ atmosphere in the 40s and 50s. Climate models then and now divide the earth’s surface into chunks then the computer calculates how the chunks interact with each other to see how things change over time. Those early models were simple but still came up with a crude picture of the earth’s atmospheric currents and its wet and dry regions. Over time the scientists could make the models mimic the actual planet by making the chunks smaller but that took more computing power. The questions like the effects of mountains on air movement, effects of carbon dioxide, and water circulation in the ocean also came up.

Luckily enough, computers were also becoming more powerful and programmers were not limited to modelling the past, present, and future. By the late 1970s, climatic models were able to start from 1850, progress through, and match the general trend in the observed temperature. By 1979, climatic models were able to project future climate albeit under different scenarios.

A report pulled from two different climate models suggested that the Earth’s temperature would increase by 1.5 °C — 4.5 °C before the end of the 21st century under the scenario that the atmospheric carbon dioxide doubled [3]. This range has proven reliable ever since.

Where are we now?

Even Though a lot has been achieved in the development of climate models and computing power, the models have not reached their perfect final form. This is because the earth’s atmosphere is an unbelievably complex system. The models cannot account for everything humans do now and might do in the future and therefore there is a lot to be done to perfect the projections. For example, UN report in 2001 and 2007 made predictions for a rise in sea-level which failed to track what was observed by satellites by about 60% [4,5]. These models were improved and the report released in 2013 increased to reflect what was being observed. Also worth noting is that small-scale processes can not be represented explicitly in models and so must be included as approximates as they interact with larger-scale features. Because of this, other techniques, such as the use of regional climate models or downscaling methods, have been specifically developed for the study of regional and local scale climate change which is helpful because people and governments in different parts of the world want to know different things.

Because of the ability of the current models to reproduce features of past climate and changes in climate, the ability to simulate important aspects of the current climate as well as the fact that the model’s fundamentals are based on already established laws increases our confidence in the models and their predictions.

From the foregoing, it is clear that the models, even though have limitations, are becoming more comprehensive in their treatment of the climate system, thus explicitly representing more physical and biophysical processes and interactions considered potentially important for climate change, particularly at longer time scales and therefore we are getting better in predicting future climate.

Where do we go from here?

According to the recently released report by the Intergovernmental Panel on Climate Change (IPCC), ‘code red for humanity’, the rate of warming of surface temperatures in Africa has been more rapid than the global average.

The newest climate model simulations project an increase in frequency and intensity of heavy rainfall across Africa [1]. The evolution of climate models should be in increasing the accuracy of climate change signals to enable the generation of location-specific climate information. This will be critical for adaptation and mitigation planning from the highest to the lowest levels of government.

References

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IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [MassonDelmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. B. R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu and B. Zhou (eds.)]. Cambridge University Press. In Press.
Rahmstorf, S., Foster, G., & Cazenave, A. (2012). Comparing climate projections to observations up to 2011. Environmental Research Letters, 7(4), 044035.
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