"Prediction is very difficult, especially about the future" is a well-known quote by Niels Bohr, the famous physicist of the 20th century. A challenge for civil engineers; after all, we design infrastructure that must operate safely and reliably for decades or even hundreds of years. Infrastructure, which involves significant public investment and where poor decisions can lead to the destruction of capital.

To illustrate the above challenge, it was observed in the 1970s that the average global temperature had been on a structural downward trend for 30 years and that the amount of snow and ice covering the Earth had increased by as much as 12% between 1967 and 1972. On 9 July 1971, the Washington Post ran the headline 'New Ice Age Coming' on an article by Dr S. Ichtiaque Rasool, the award-winning Chief Scientist for Global Change at NASA. In this article, he predicted that increased fossil fuel emissions would lead to a significant drop in average global temperatures. However, the Royal Netherlands Meteorological Institute (KNMI) models now indicate the opposite: heat waves with temperatures exceeding 40 degrees Celsius will become almost annual occurrences towards the end of this century.

Fortunately, we are becoming better at dealing with (climate) uncertainties. Firstly, the United Nations' Intergovernmental Panel on Climate Change (IPCC) is taking a more nuanced view of the future. Using different Shared Socio-Economic Pathways (SSPs) and taking the dynamic and particularly complex climate system and uncertainties into account, its latest Assessment Report 6 (AR6) portrays a wide range of potential scenarios regarding global CO₂ emissions, temperature, sea level rise, etc.

Secondly, civil engineers now seem to be the most appropriate specialists to address the many uncertainties. Managing uncertainty is the essence of (probabilistic) design. Rather than choosing one specific future, we choose to achieve an optimal design solution that incorporates a wide range of potential future load scenarios and their probabilities in relation to the strength of the structures and systems in a balanced and rational way. The development of this design method has made great strides in civil engineering in the Netherlands since the design of the Eastern Scheldt storm surge barrier (Oosterscheldekering) in the 1970s.

Probabilistic design
Probabilistic design explicitly accounts for risks and uncertainties by mapping the possible variation in material strength for all structural components, including the probability for each of these strengths. The components are subjected to all potential future loads resulting from (changing) use, climate change and possible events such as fire, lightning, storm, flooding, long-term drought, etc., including the probability of occurrence. By designing the structure so that the likelihood of exceeding the strength during the design life is (slightly) less than the legally acceptable risk of failure, we create an optimal structure that performs its functions with sufficient reliability at minimum cost.

In addition, we take advantage of the dynamic nature of climate change by designing adaptively and thus 'buying time'. With adaptive design, we prepare the structure to adapt to changing (climatic) conditions in the future, thus preventing us from making the 'wrong' decisions now and incurring unnecessarily high (lifetime) costs and/or releasing unnecessary pollutants.

The Paris Climate Agreement, signed by the European Commission in 2016, was converted into the Dutch Climate Agreement in 2019. An agreement between governments, businesses and public organisations with the aim to reduce greenhouse gases in the Netherlands by 49 percent by 2030 compared to 1990. Although developments in sustainability are accelerating, the question is whether this will be achieved. Moreover, climate change is happening regardless, and we are already experiencing its consequences. At the insistence of the European Commission, the Netherlands drew up its National Climate Adaptation Strategy (NAS) in 2016, which was adopted by the House of Representatives at the end of 2017.

The reduction of greenhouse gas emissions and the probabilistic and adaptive approach described above form the basis of Iv's sustainability vision. We implement sustainable (diagnostic) asset management and climate-proof designs according to the 'Butterfly Diagram' developed by the Ellen MacArthur Foundation. This model describes the continuous flow of biological (green side) and technical (blue side) materials within 'value circles' in a circular economy. The aim is for raw materials, components and products to retain their value for as long as possible. This forms part of our day-to-day work: Keeping civil engineering works safe for as long as possible, thereby saving on the use of materials. We design new structures that are as innovative and sustainable as possible and focus on climate adaptation and reducing the use of raw materials. Furthermore, we investigate the origin of raw materials to help us design as circularly as possible.

In our sustainability vision, the focus lies on the technical (right) side of the Butterfly Diagram, where our infrastructure is represented in stages by the following circles: User → Maintain/Prolong → Reuse/Redistribute → Refurbish/Remanufacture → Recycle → Waste. In our design and asset management approach, we strive to achieve the optimal solution within the following set of conditions:

When designing new and existing infrastructure and land use plans, we work as probabilistically as possible and base our designs on a range of future scenarios. We explore innovative ways to apply adaptions and reduce greenhouse gas emissions.

In the latter context, we aim to reuse the structure or installation as integrally as possible, possibly in an adapted form. This may involve 'moving' a bridge to another location or reusing bridge girders. The final circular fallback option is to recycle materials, such as concrete, wood and steel, among other materials, into usable raw materials for new applications. Finding a replacement solution for the complete or partially dismantled structure or installation is often necessary in these situations. We apply the same conditions to new construction and replacement as in asset management. Wherever possible, we choose reusable materials or components and strive to minimise the CO₂ footprint during the realisation and use of the structure and minimise the maintenance required. We also design dikes and embankments using local soil to reduce the number of transport movements. With this sustainability vision, Iv optimally, rationally and responsibly implements the Climate Change Agreement and the National Adaptation Strategy in civil infrastructure. Not by predicting the future with precision but by addressing (future) uncertainties in the best possible way. After all, we would rather be right about being uncertain than definitely wrong.