Glacial, Icecap and Permafrost Melting XLVII: Cordillera Blanca, Peru, 2008 © Sayler/Morris
How Humanity Changes Climate – A Calculation Model
The past summer in Europe has been extremely hot and dry – the new normal or an exception to the rule? With Dr Friederike Otto, we take a look in the mirror to acknowledge the consequences of man-made climate change as our reflection increasingly gains profile with the help of attribution science.
Dr Otto, you have co-founded the discipline of “Attribution Science”. When you are talking about climate change in your research do you refer to a natural process or the man-made influence on the climate system?
When I talk about climate change, I explicitly mean the man-made, the anthropogenic climate change. Obviously, climate will transform over a certain amount of time without any human assistance, but indisputably, we are currently living in the Anthropocene, meaning a time when humans have a substantial influence on climate processes.
What exactly is the field of attribution science?
“Trend Attribution” is an important and well-researched section of attribution science, which deals with the rise of the global mean temperature, its driving factors and ramifications, so with the long-term consequences of climate change. Admittedly, we have known for a long time that the global mean temperature is rising but this factor alone will not kill anyone directly. However, indirectly it could, mainly through the increased probability of extreme weather events. This is where my research becomes relevant. After the occurrence of an extreme weather event, I try to understand what role climate change has played in the process. I call this approach “Event Attribution”.
How do you make the influence created by humans tangible?
Every extreme weather event is the result of an interplay of various driving forces. Out of this multiplicity of driving forces, we try to isolate the influence of climate change. Our approach is very simple. We determine the probability of a weather event occurring within the world we live in today, and compare this result to the probability of the same event occurring in a world that is just like ours but omits climate change caused by humans. The influence that humanity has on climate change can be narrowed down by comparing these two results.Thus, we are interested in the whole spectrum of possible weather occurrences within the given climate conditions. This is why we cannot derive the probability of a specific weather event occurring from simply looking at how often that specific event has occurred in the observed record. We have to simulate the possible weather events in the form of climate models. The basic idea of this approach is very simple, the execution however is still difficult as it requires high-quality observational data, high resolution climate models and an establishment of a strong connection between the real world damages, and a weather event that can be observed and simulated reliably.
How is a climate model created?
There are three basic principles of physics which determine the climate: the conservation of energy, the conservation of mass, and the conservation of momentum. In the climate model, these three basic principles are implemented as differential equations. The problem here comes from the conservation of momentum which is Newton’s second law. This law for the atmospheric circulation is called the Navier-Stokes equation which can be written down but cannot be solved analytically, and also numerically not everywhere you’d in theory like to, due to the giant effort that would be necessary to calculate the movements of every single particle in the atmosphere. This is why the equation is solved numerically at discrete points only. For that, the world is arranged in a grid so that the equation can be solved at the grid points and not in the spaces in-between. The resolution, meaning the density of the grid points, is the crucial difference between climate and weather models. Principally, a climate model is nothing else but a weather model with a lower resolution.
For your project “climateprediction.net” you do not rely on the processing power of one central mainframe but on the capacities of thousands of volunteers instead. Their private computers are running your climate models. Hands-on research. Is that a way to create a higher resolution model?
Exactly. For example, Europe is covered with a grid that has grid points every 25 kilometres. Distributed computing gives us the advantage of being able to run many more simulations for possible weather events. With a modern mainframe and a lot of money, we would be able to maybe run 50 simulations but because of our method, we can calculate possible weather events under the given climate conditions up to 1,000 times. Without this project, we would probably be ten years behind our current state of research.
“The U.S. greenhouse gas emissions made the heatwave in Argentina 30% more likely to occur”
If we talk about proof for the man-made influence we would also have to discuss responsibility or rather blame. Can such concepts be allocated within a complex system like our climate?
That depends on how you define it but the short answer is ‘yes’. For example, for one of our studies we looked at U.S. greenhouse gas emissions and their influence on three extreme weather events: a heatwave in Argentina, extreme rains in England, and a heatwave in the Arctic. In science, you never get one absolute number as a result, but a margin of uncertainty.In our study, we found that within this margin of uncertainty it can be concluded that the U.S. greenhouse gas emissions made the heatwave in Argentina 30% more likely to occur. However, such studies depend on certain assumptions which each impacts the result. In general, these assumptions rather refer to political or social dimensions. For example, looking at all of the historic emissions in the US since the beginning of the industrial revolution rather than just from, say, 1990 when the first report of the IPCC (Intergovernmental Panel on Climate Change) –which made the consequences of emissions well-known in the first place – was published. The result is obviously a very different one but asking which timeframe is the right one is just no scientific question.
Due to your work on the World Weather Attribution project, you have also done research on the 2018 heatwave in Europe. What was your conclusion?
In this case, there is not just one conclusion but actually seven, since the definition of “heatwave” means something different for each of the seven cities we looked at. However, the general result shows how, from a meteorological viewpoint, the heatwave was not an extreme event, except for some cities located in the very north. It was an event that can be expected to occur every five to ten years even though the highest temperatures had broken records. This shows what it means to live in a world with a strong trend, where record-breaking temperature occurrences are no longer being seen as extreme events from a meteorological point of view due to how more likely they are to occur. From an attribution point of view, it has also become apparent that the likelihood of extreme weather events has distinctly increased because of man-made climate change. Depending on the city, the probability of an occurrence has become two to five times more likely.
“Looking at the distance between cause and consequence partly explains the issues”
In 2018 you went to Katowice (Poland) for the climate summit which ended in disappointing results. Your research delivered proof of human influence. From a Kantian perspective, what is holding us back from using reason and counteracting climate change?
That is a very loaded question. For the most part, there is the issue of perception. Emissions which are, for example, emitted in Asia or America lead to climate change all around the world and not just within the immediate surroundings of the locations and the impacts are very inhomogenous, apparently only affecting far away countries. Looking at the distance between cause and consequence partly explains the issues that arise when trying to handle climate change. However, climate change is not something that will happen sometime in a far away future in a place far away. It is happening right here and now, even where we live. The probability for heatwaves in Europe has obviously gone up considerably, nonetheless, the summer of 2018 was a pleasant summer for most Europeans. Climate change is not being perceived as something which is threatening our very existence. I also believe that a majority of all people have a hard time imagining a lifestyle that excludes fossil fuels.
Cue the term “lifestyle” – climate change is also being called a “catastrophe without event” because the continuation of our daily routines leads to a catastrophe. Is the crux to break with this continuity?
I believe that the fight against climate change does not differ from other processes of societal progress in general. Every advance we make as a society is faced by a certain degree of opposition. Currently, the best way to understand the opposition to change is by looking at the AfD or Donald Trump’s politics, which is all about the attempt to stop societal progress by creating physical or psychological barriers. I believe that the reasons for this reactionary position are basically no different from the reasons which deter an active fight against climate change.
Bangladesh is seen as one of the hotspots for climate change. How do the local politicians react to that?
For a developing country, Bangladesh invests a lot into science and research. Also, as far as I know, Bangladesh is the only country in the world that has created a Loss and Damage-Fund. The term “Loss and Damage” encompasses all damages which resulted from insufficient or unattainable adaptations to climate change. After years of solicitation from the least developed countries, the 2016 Paris climate agreement incorporated the term and all its implications. That might be the best proof for developing countries being capable of having a great influence on the international stage. Nonetheless, the Paris agreement is very vague in its explanation and their recommendations on how implementation would work. Bangladesh on the other hand, put a part of their national budget to the side to be able to help in the case of climate-caused damages.
What role is attribution science playing in terms of compensation claims?
As far as I know, none of the money Bangladesh had allocated has been paid out because the question of what is part of “Loss and Damage” is very difficult to answer. The actual problem is the question of distribution. For example, if an event only shows a low probability, do those affected only receive little money? This aspect entails many difficult social questions which is why the definition of “Loss and Damage” is almost non-existent in the Paris climate agreement. At some point, there needs to be an agreed definition that can work as a base for further discussion.
Is that the reaction to your research you are hoping for: compensation in the case of damages?
It would be fantastic if my research could actually contribute to more justice in climate matters. I am sceptical if my research is suited to actually lead to more feasible compensations. The availability of data is often not sufficient enough and the climate models that are available to us today have their limits. That is why attribution science is a tricky base to build upon in order to calculate any loss and damage claims. What I am primarily hoping for is that we – and I am also including us scientists – gain a more realistic understanding of what climate change actually means due to us not having any overview of the ramifications up until now. All the attribution science that we have worked on over the past years has given us something to highlight here and there but it fails to yield a complete picture of the consequences. On the one hand, I hope that we will be able to isolate climate change hotspots in the future. On the other, it is important to be able to better differentiate which climate events are influenced by climate change and which are not.
What are the specific contributions of your research to more justice in climate matters?
On a basic level, my research can contribute to the ability to communicate in numbers who is actually affected by man-made climate change. It is a big issue that we are lacking the necessary data due to the lack of measuring stations, especially in the poorer parts of the world. This means we do sometimes not know what the “normal” weather really looks like in these regions, disregarding extreme weather events. Consequently, we do not have any reference figures for our climate models. Even within climate modelling we are confronted with a certain degree of eurocentrism due to the climate models working best in the areas they were designed in. None of the world-wide accessible climate models were developed in Africa. Because no climate model is perfect, compromises are unavoidable and most of the time the compromise consists of the model working best in the area it was developed in at the expense of the rest of the world. The problem is not just the observational data but also the distorted models. This is where it comes full circle because the appropriate models cannot be developed without observational data.
“Even within climate modelling we are confronted with a certain degree of eurocentrism”
New-Zealand estimated that climate-caused damages to its country over the last ten years have amounted to 840 Billion USD. You have voiced the opinion that all countries should establish a balance showing all damages caused by climate change. Why is that?
To stress that all preventive measures are expensive but much more so is deciding to stay inactive. The objective that staying passive will be expensive and already is at this point in time, is often overlooked in discussions about renewable energies. In New Zealand, they did just look at the attributable impact of droughts and floods to come up with a conservative calculation. Thus, that number is the absolute floor of the caused damages. Of course, just the assessment of damages does not do much on its own but it functions as a basis for arguments which try to justify the shutting down of a coal plant, for example.
The German philosopher Günther Anders once said that “Man throws further than he can see.” How much can attribution science contribute to bridging the created gap between our short-sighted actions in the present and the resulting repercussions in the future?
On the one hand, attribution science can add to the perception of climate change by making its influence on extreme weather events more visible. However, the crucial step is surely the connection of attribution science and climate projection, meaning the connection of past and future. For example, if we look at the European heatwave last summer. Without climate change that would have been an event that occurs maybe every 30 to 40 years but with the global mean temperature rising even one more degree we will experience a summer like that every other year. This way it is so much easier to distinctly show what a rise of one or even one and a half degrees in temperature would mean. Otherwise, 1.5 or 2 degrees are only politically charged figures which nonetheless remain very abstract in what they express. In my opinion, it is possible to bridge the gap mentioned by Günther Anders by trying to establish the connection between the already experienced and whatever the future will bring.
That makes it sound like prevention.
Of course, if we use the methods which were developed for attribution science to make predictions at specific locations. If we know what kind of event a region or a city is vulnerable to, we can – even without the specific event taking place – say how the likelihood is changing for such an event to even occur and how to best plan and prioritise adjustments.
You have voiced a cautious optimism about the way climate change is being dealt with. However, the GHG-emissions have gone up 3% in 2018 which makes it appear like we do not know anything about climate change. How can you stay optimistic?
Just the fact that the Paris climate agreement even exists and that it was signed by all states is, from a climate political point of view, way more than what was to be expected in the beginning of 2015. On the other hand, in my judgment, it is a generational issue. For our generation, it is very obvious that anthropogenic climate change exists. This trend will progress for generations to come and it will not be much longer until these are the people who make all the important choices. I think that this is what makes me feel optimistic.
Dr Friederike Otto is the Acting Director of the Environmental Change Institute at the University of Oxford and Associate Professor in the Institute’s Global Science Program. Furthermore, she is the co-founder of the “World Weather Attribution” project and has contributed significantly to the implementation of the open-science project climateprediction.net. Her research focus of attribution science concentrates on the influence of human beings on the probability of extreme weather events.