Climate change: "An experiment with the earth, that must be stopped"

Dr Ceppi next to Coleman Glacier on Mount Baker in Washington State.

Dr Paulo Ceppi, Imperial College Research Fellow, warns that we’re running a dangerous experiment with planet earth.

Dr Ceppi's research specialises in understanding how different elements of the climate system react – and contribute – to warming, in order to better predict what future climate change looks like. Before he joined Imperial College London, he was at the University of Reading, where he won the 2018 Best Research Output Prize.

We’re running an experiment with the earth – scientifically it’s fascinating, but we should stop the experiment. Dr Ceppi

In particular, his work seeks to understand how clouds and the circulation of the atmosphere change as greenhouse gas concentrations rise and the planet warms. On a purely scientific level, Dr Ceppi thinks climate change is a fascinating, albeit risky, experiment. "Usually we only get to see what happens when we run a model. But we’re running an experiment with the earth itself," he said. "It’s fascinating science, but we must stop the experiment."  

We caught up with Dr Ceppi to find out more about his career and ambitions:

Did you always want to pursue an academic career in climate science? 

I began university in Geneva, Switzerland, studying international relations. However, a year later, I made the switch to science. I have always found weather forecasts fascinating. Ever since I was a child, I have had a passion for weather and climate, so studying the science of climate change seemed a natural step for me.   

Can you briefly describe the focus of your research? 

At the Grantham Institute, I’ll be pursuing two lines of research. One is focused on understanding climate sensitivity - looking at how much warming will result from a doubling of carbon dioxide in the atmosphere. This question very much depends on 'climate feedbacks', which refers to how components of the climate system change as the planet warms. For example, if sea ice melts, there will be less ice to reflect sunlight; the planet will absorb more sunlight, so the planet will warm even more. This is an example of a positive climate feedback.

The more we warm the planet, the more likely it is that something will tip over and cause accelerated climate change. Dr Ceppi

I am particularly interested in feedbacks involving clouds, such as how they change as temperatures rise, and how they contribute to increased levels of warming. Currently, climate models are bad at simulating feedbacks like these. With my second research area I'll be trying to gain a better understanding of these feedbacks by using recent satellite observations of clouds, in order to improve how they are incorporated into our models.  

What do you think has been the biggest change related to climate change and the environment in recent years? 

Over the past ten years, computational power has increased enormously. This means we can calculate much more complex climate simulations, for example better representing variables like precipitation, clouds and the flow of the atmosphere. This is particularly helpful for those of us interested in clouds, which are remarkably hard to model. Thanks to the improved computational power, we are making progress towards understanding how clouds might change with global warming. 

What would you like to see happen in the next few years?

From a science perspective, the big challenge for the next few years is trying to further reduce our uncertainty about how the climate system will react to future warming. This will enable us to better predict exactly what could happen under certain scenarios of the future, with different levels of greenhouse gases in the atmosphere.   

From a practical point of view, it needs to become easy for ordinary people to make environmentally friendly choices – like when they go shopping for clothes, food, or insurance. You can’t tell people what to do. It needs to be made easier and cheaper for people to live their lives and protect the environment together.  

Are you optimistic the world will meet the challenge of climate change?

I don’t think the big changes that we need will happen in time for us to keep warming below the two degrees Celsius stipulated in the Paris Agreement. Sadly, I think we will see big changes in the climate system, such as significant warming, sea level rise and extreme heatwaves before real action is taken. 

What concerns me most is that we don't know enough about climate 'tipping points' – the critical thresholds when climate changes from one stable state to another. We don’t know when they might be triggered, and we can’t rule them out. The more we warm the planet, the more likely it is that something like melting Antarctic ice sheets, or methane released from frozen grounds, will cause accelerated climate change (as described in the recent Hothouse Earth study). This is a big motivation to keep warming levels as low as possible. 

What drew you to Imperial College London and what are you most looking forward to in the next four years?  

The climate research community is great in the United Kingdom. Lots of institutions are carrying out high quality research and running complex climate models – and Imperial is one of them. It’s a fantastic university with highly qualified scientists and outstanding students, who I’m looking forward to working with. Collaborating with other people and explaining your research to them – whether colleagues or students – gives you a different perspective and enriches your work.  

What do you think is the most important thing about communicating climate science to the general public?  

People need to understand the science behind climate change, so it’s important to explain the basic physics involved in a way that everyone can understand. We also need to be honest about the limits of our understanding. Sometimes, we simply can’t say whether climate change made something more likely. We have to acknowledge that and instead explain how climate change relates to weather and changes the odds of extreme weather happening. It’s a delicate balance; if you are too alarmist, people get tired of the warnings.