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How to forecast the future with climate models

How to forecast the future with climate models

Our climate is constantly changing, and with the help of simulation modelling, scientists are working hard to better understand just how these conditions will change and how it will affect society. Science journalist Conor Paul Purcell has worked on Earth System Models during his time as a PhD student and postdoctoral researcher; today he explains how scientists use these models as tools to forecast the future of our climate.

While we can’t predict everything about our future, climate scientists have a good understanding of how our environment will look and feel like in the coming years. Researchers and climate specialists predict that temperatures will increase dramatically in the 21st century, ranging between 1.5°C and 4°C above pre-industrial levels, depending on your location and the amount of carbon dioxide pumped into the atmosphere in the near future. Forecasts of future drought and flood risk, at both regional and global bases, are also provided by climate experts.

Understanding how such features of Earth’s changing climate may manifest, and ultimately impact on our society, takes considerable international collaboration – a collaboration which is largely based around the results of climate modelling. That’s because climate predictions for the future are made using sophisticated computer models, which are built around mathematical descriptions of the physical and biological processes that govern our planet.

These models have become so complex in recent years that they are now referred to as Earth System Models (ESMs). Using ESMs, climate modellers can create simulations of the planet at different times in the future and the past. ESMs are in fact the only tools we have for simulating the global future in this sense. For instance, if we want to know how our climate may look like one hundred years from now, how ocean acidification levels may change and how this might impact ocean life, or how plants will respond to increasing levels of atmospheric carbon dioxide, ESMs are the only tool available.

The models are built in components, each representing a separate part of the Earth system: the atmosphere, the ocean, the land surface and its vegetation, and the ice-sheets and sea-ice. These are constructed by coding each component with the mathematics that describes the environmental processes at work.

Climate models are systems of differential equations based on the basic laws of physics, fluid motion, chemistry, and biology. Pictured here is a schematic of a global atmospheric model. (Credit: NOAA, via Wikimedia Commons)

For example, the winds in the atmosphere are described by the mathematics of fluid motion. Model developers translate these mathematical equations into code that computers can understand, like giving them a set of instructions to follow. Supercomputers can then interpret the code to simulate how winds, for example, are expected to develop at each global location through time. The results are usually plotted on world maps.

As scientists have learned more about our Earth’s systems over time, the complexity of these individual models has been ramped up dramatically. For example, the land surface and vegetation model components become more sophisticated as plant biologists understand more and more about how plants transfer water and carbon between the land and atmosphere.

And it’s not just one giant solo project either: there are tens of ESMs and hundreds of subcomponent models developed and used at research centres around the globe. Collaboration between these facilities is a necessary part of progress, and information is shared at international conferences ever year, like the American Geophysical Union’s Fall Meeting in the United States and the European Geosciences Union’s General Assembly in Europe.

This means that developments are always been made towards increasing the realism of ESMs. On the horizon such developments will include increasing the resolution of the global models for improving accuracy at regional locations, and also incorporating the results from the latest research in atmospherics, oceanography and ice sheet dynamics. One example is research into plants, specifically how they interact with carbon dioxide and water in the atmosphere. Further understanding of this biological process is expected to increase the realism of models over the coming years and decades. In general, improvements to the accuracy of model simulations can help to help society in the future. For example, models will be able to help predict how climate change may impact, say, water scarcity in South Africa, wildfire risk in the western United States, or crop yields in Asia. Indeed, the ESMs of the future should boast incredibly accurate simulations and prediction capabilities unheard of today.

By Conor Purcell, a Science & Nature Writer with a PhD in Earth Science

Conor Purcell is a science journalist with a PhD in Earth Science. He is also founding-editor of www.wideorbits.com and is on twitter @ConorPPurcell and some of his other articles at cppurcell.tumblr.com.

Floods and droughts set to increase due to climate change

Floods and droughts set to increase due to climate change

The planet is set to encounter a record-level amount of floods and droughts by 2050 – researchers recently announced at the European Geosciences Union’s General Assembly in Vienna. Nikita Marwaha shares their predictions on the impact that climate change will have on these extreme weather conditions.

In a study by the Joint Research Centre (JRS) – the European Commission’s in-house science service – new climate impact models are being used to determine future flood risk in Europe under conditions of climate change. These state-of-the-art models, presented by JRS scientist Lorenzo Alfieri, indicate that the change in frequency of extreme river discharge is likely to have a larger impact on the overall flood hazard than changes in their magnitude.

“We predict a 150% increase in future flood risk by 2050”, Alfieri said. This dramatic increase will trigger the so-called “floods of the century” that we currently experience every 100 years, to double in frequency – submerging much of Europe under water within the next few decades. As a result, the extent of damage and number of people affected are expected to increase by 220% by the end of the century.

With more lives predicted to be touched by this climate change-induced flooding, it is of utmost importance to accurately calculate projections of future flood events and to assess the situation that our planet faces. In this study, the JRC applied the most recent climate change projections to assess future flood risk in Europe. Using statistical tools and dedicated analysis, flood simulation was carried out to evaluate changes in the frequency of extreme river discharge peaks.

These projections of future flood events were then combined with data on the exposure and vulnerability of populations, in order to estimate the overall flood risk in Europe under a high-emission climate scenario. Socio-economic scenarios were also investigated. The research addressed both current and future scenarios – with the dates of 2020, 2050 and 2080 used in the socio-economic impact models of large, European river floods.

Satellite picture of Europe. Land terrain and bathymetry (ocean-floor topography). Credit: Koyos (distributed via  Wikimedia Commons)

Satellite picture of Europe. Land terrain and bathymetry (ocean-floor topography). Credit: Koyos (distributed via Wikimedia Commons)

Alfieri estimated that between 500,000 and 640,000 people will be affected by river floods by 2050, increasing to 540,000 – 950,000 by 2080, as compared to 216,000 in today’s climate. A wider range was found for the annual economic impact of flood damage. It is currently estimated at 5.3 billion EUR, set to rise to between 20 and 40 billion EUR in 2050 and to between 30 and 100 billion EUR in 2080. Such predictions are dependent on future economic growth, resulting in the larger range of figures presented at the conference.

Another extreme weather condition that the planet faces is drought – said to increase before the middle of the century. Yusuke Satoh, a researcher from the International institute for Applied Systems Analysis (IIASA) shared new research suggesting that some parts of the world may see unpreceded levels of drought before 2050. These new findings urge swift action to be taken to adapt reservoirs and water management policies in accordance with the depleting water resources.

“Our study shows an increasing urgency for water management systems to adapt for future drought”, Satoh said in a statement at the press conference. “In order for policymakers to plan for adaptation, they need to know when and where this is likely to happen, and have an understanding of the levels of uncertainty in such projections”.

Droughts are predicted to grow more severe and frequent by 2050 for 13 of the 26 countries mapped by the organisation. A new measure was proposed in this study – Timing of Perception Change for Drought (TPCD). This drought will surpass all historical records and countries will reach TPCD at varying times – with western United States feeling the effects as early as 2017, and the Mediterranean by 2027, at current emission rates.

The new study by IIASA combined five different global climate models to examine two different scenarios for future climate change – a 1°C and 3.7°C rise in temperatures by 2100. This technique allowed researchers to address the uncertainty of our planet, since climate change is a manmade environment issue that is difficult to accurately foresee using just one climate model.

From this research, the predicted arrival date of these record-breaking droughts was found to be more uncertain in the Sahara, sub-Saharan Africa and South Australia regions, with certainty very high in southern South America and the Central United States.

Being aware of where the uncertainty lies in the world is important. It allows policymakers and water resource managers to prepare for greater future variations in water availability, since the historical data that the hydrological structures of today are built on, will eventually become void as climate change carves new figures into the history books.

Satoh advised measures such as releasing water from reservoirs during the dry season to relieve the onset of future dryness. “The earlier we take this seriously, the better we will be able to adapt”, he said.

Controlling the amount of seasonal water precipitation and water use, will allow us to manage both the natural and manmade causes of hydrological drought – giving us better control as the effects of climate change begin to set in.

By Nikita Marwaha, EGU Press Assistant and EJR-Quartz Editor