THE bush fires that engulfed parts of Australia earlier this year were nothing short of apocalyptic. More recently, a record-breaking heatwave has hit Siberia, causing a thaw in the permafrost that contributed to one of Russia鈥檚 worst ever oil spills. But were these disasters caused by climate change?
For a long time, scientists have said that we can鈥檛 pin any single extreme weather event on our greenhouse gas emissions. That is still true, but in recent years, researchers have become far better at estimating how much more probable any given 鈥渘atural鈥� disaster was made by human-caused global warming.
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This work is called extreme event attribution, and it involves comparisons between real observations of weather events and computer simulations of a world with and without the roughly 1掳C hike in temperatures caused by humanity so far. Run the simulations thousands of times and you can calculate the odds of the event occurring in both scenarios. So you can say, for example, that the drought conditions that were responsible for the Australian bush fires were made at least 30 per cent more likely by climate change. Or that human-induced global warming made the rise in temperatures that have been seen in Siberia over the past few months at least 600 times more likely.
Friederike Otto at the University of Oxford, who led the team behind the rapid-response studies that made both of these estimations, is at the vanguard of the field. As co-founder of the World Weather Attribution project, she has been pivotal in recent work that has significantly sped up the process.
Attribution already occurs in a matter of weeks, but soon it could happen within days. And Otto thinks that a change of this sort could have a profound effect on efforts to strong-arm governments into tougher action on carbon emissions. What鈥檚 more, attribution could even soon be used as evidence in legal cases in which people affected by extreme weather make claims for damages against governments or fossil fuel companies.
Adam Vaughan: How do you describe your job to people?
Friederike Otto: I鈥檓 trying to answer the question of whether, and to what extent, man-made climate change altered the likelihood and intensity of recent extreme weather events. The data-processing aspect of that is a very small part of my work. Most of my day-to-day work is thinking about the most appropriate data sources to use for these kinds of studies, or which models should be used, or how we can test the models better to see whether they are able to reliably simulate the weather event.
What developments have moved your field along? Is the progress purely down to better data and more computing power?
Actually, the big advance has been that we have realised how important it is to understand what question you鈥檙e asking. You can define a heatwave as unusually high summer temperatures over three months, and you will find that climate change made it orders of magnitude more likely. But you can also define a heatwave as a very local thing, as the heat stress that affects the human body, which depends not just on temperature, but humidity too. In that case, you will find that climate change maybe doubles the likelihood.
If you are interested in mortality because of a heatwave, you will frame it differently to someone interested in agriculturally relevant summer temperatures. What we do have convergence on is methodology: there is agreement that we need to use at least two different models for every calculation to understand the errors they can produce.
In a warmer world, we can expect more extreme events like the drought that preceded the Australian bush fires. Is that going to make attribution easier or harder?
The main difficulty is in whether we have models that really represent the processes behind extreme weather events. For example, do we have models that are able to simulate strong enough hurricanes in the first place? That doesn鈥檛 really change with increasing temperatures. On the other hand, the signal of human-caused climate change gets bigger with increasing temperatures, so it is getting easier to disentangle it from the noise.
What has attribution achieved so far, and what is next for this science?
I think the impact so far is really in raising awareness of the fact that climate change is happening right now, and that wherever you live in the world, there are damages from extreme events that you would not have had without climate change.
On what comes next, one of the things I鈥檝e learned relatively recently is that it would be better not just to say the weather today has changed because of climate change, but also to say something about what that means in the future. So now we have a world that is 1掳C warmer than in pre-industrial times. How would weather patterns change in a 2掳C-warmer world?
We do not only want to understand what climate change means right now, but what we will need to adapt to. Which are the types of events and areas of the world where climate change is a real game changer, so that we have to completely alter how we deal with the impacts of such events? With limited resources, it is important to understand where to best focus them.
I understand you are also looking at whether attribution could be used as evidence in legal cases in which people claim for damages against companies or governments.
The legal community is realising that this is now a possibility. In many older climate litigation cases, the reason for not admitting evidence that humanity鈥檚 greenhouse gas emissions are to blame for extreme weather events and the damage they cause, was that you can鈥檛 say the chain of causality is complete. But I鈥檝e been working with lawyers to see whether you can use attribution studies in courts in a meaningful way. We are not far off seeing successful cases using that kind of argument 鈥� in one, two or three years.
The way society sees climate change has changed too, and judges are a part of society. It would be very strange if that shift in public perception would not also filter through to the courts; that understanding that climate change and the damages it causes are real.
鈥淲herever you live, there is damage from extreme weather that you wouldn鈥檛 have had without climate change鈥�
You have said before that the results of attribution studies are quite conservative. Is that still true? And does it really matter, given that they still reveal the link between extreme weather and climate change?
At the moment, especially with heatwaves, we can only give a lower bound: we can say OK, climate change made it at least 30 per cent more likely. It would be better to be able to also at least quantify the upper bound. So that is a problem. If you want to quantify damages, and if you want to understand the extent of the adaptation measures you are going to need to put in place, such as higher flood defences, then you need more detail.
We seem to be good at doing attribution studies for events in the developed world, but not so much in poorer countries. Is that a problem?
We absolutely need to redress the balance. On the one hand, it would help us to understand what climate change means globally. But more than that, if we really want to adapt to climate change, understanding the extreme cold snaps in the US, for example, might not be the most important thing. It might be more important to understand the droughts we see in East Africa. At the moment, there is no evidence that climate change is causing migration from eastern Africa, but it is a question we must address. We can鈥檛 just ignore parts of the world and think it doesn鈥檛 affect the rest of us.
With respect to responsibility, I believe Europe should not complain about migration completely independent of climate change. But from a causality point of view, attribution studies do allow for a better understanding of the consequences of our political decisions, and that does beg questions of responsibility too.
You grew up outside the city of Kiel in northern Germany, and your mother was a teacher and your father a biologist. How did your upbringing shape you?
My parents were hippies. They were the 鈥�68 generation, protesting on the streets for social reforms and sexual freedom. It was very much not a conservative household. They lived in the middle of nowhere because they found that very romantic. Mainly, it meant a relatively lonely childhood. And I just read. I still live half my life in novels. Above all, though, what my parents gave me was a tendency to question norms and rules.
Germany is often held up as a world leader on climate change because of renewables, but may take until 2038 to phase out coal, while the UK currently plans to do so by 2024. How well do you think Germany is doing in tackling carbon emissions compared with the UK?
It is very good at talking but very bad at doing. I think Germany is an example of how not to do it because it implies it is this green leader, but German politics is still to a large degree dictated by the car industry. There are a lot of things very wrong with UK politics, but on climate change, the way it has approached this has been better.
Still, it鈥檚 not great. Its words still need to be followed up with legislation. But it is encouraging that the UK government did announce a net-zero emissions target very early, it has science-based adaptation plans and it has the Committee on Climate Change, which is bringing science directly into government.
What do you think the covid-19 crisis means for the fight against climate change?
What I鈥檓 worried about is people thinking we have to do the same things we鈥檙e doing to tackle coronavirus to tackle climate change. It could reinforce this fear that climate action would completely disrupt the economy. What we need to do for climate change is very, very different. The changes have to be long term, so you don鈥檛 shut down the economy, you just change things 鈥� and there are a lot of winners and a lot of things that are better in that scenario. In that sense, it鈥檚 an opportunity. In our plans for economic recovery after coronavirus, we have to think about climate change.
How optimistic are you that we are going to get a handle on reducing emissions globally?
I鈥檓 very optimistic we will have a world we can still live in. One of the main reasons for hope is what has happened in the past two years in terms of how the conversation has changed on climate change. For most people in my generation, and definitely the people in the younger generations, climate change is something that is important and there鈥檚 no question that it鈥檚 something that needs to be tackled.
