Ask a climate scientist: What the past can teach us about our future climate

If you’ve ever dreamt of jumping back in time to find out what the Earth looked like millions of years ago, you’ll definitely want to read this. We sat down with Dr. Sebastian Steinig, a postdoctoral researcher studying how and why climate has changed in the past.

Using numerical models and paleoclimate reconstructions (data on ancient climates), his research focuses on past warm periods like the Cretaceous (around 100 million years ago), and how they can help us understand and predict future changes in the climate.

Among his academic projects, Dr. Steinig recently developed the climatearchive.org website, an interactive visualization of climate models across time and space that enables everyone to interact with and explore climate science in a way as easy as using Google Earth. For him, making climate science accessible to the wider public is essential to combat global warming. Ready to learn about paleoclimatology? Let’s start with the basics. 

How do you reconstruct past temperatures? Which kind of data do you need to do this?

We can reconstruct past climate change from a wide variety of geological and biological records. These “natural archives” record the passage of time and can show us the climatic conditions of different eras. Annual tree rings are one of the most well-known climate archives and can be used to reconstruct changes in temperature and precipitation over the last hundreds, sometimes even thousands of years. We can also use small air bubbles trapped in ice cores from Antarctica and Greenland to get actual samples of the ancient atmosphere. 

This allows us to directly measure concentrations of gases like carbon dioxide and methane for the last 800,000 years. But we can even travel further back in time! Large drill ships can recover sediments from the ocean floor that accumulated up to 200 million years ago — at a time when dinosaurs roamed the Earth. Tiny fossils in these sediments and their chemical composition can reveal amazing information about the paleoenvironments that they lived in.

How can past climates help us predict future climate change and the consequences it will have on the Earth?

Reconstructing past climates is the only way to actually observe how Earth adapts to changes in atmospheric carbon dioxide concentrations. The geologic record provides incredible examples of past climate change, ranging from the exceptionally warm and ice-free mid-Cretaceous (92 million years ago) to the peak of the last glacial period (21,000 years ago), when up to 25% of the global land area was covered by thick ice sheets. Therefore, understanding how and why Earth's physical, chemical, and biological processes have changed in the past is key to better predicting what our own future might hold for us.

Past climates also provide a unique opportunity to test our current climate models against data outside of historical weather records from just the last one or two centuries. Models that can better reproduce the extreme variability found in the paleoclimate records are also more likely to accurately predict future climate change. This provides a great opportunity to reduce uncertainties in our climate projections for the coming decades.

How does human-driven climate change differ from natural climate change in terms of its effects on the Earth?

The fundamental difference is the speed at which we are currently warming our planet. Earth’s climate is an incredibly dynamic system: Large swings in atmospheric carbon dioxide happened throughout the geologic past, but on timescales of thousands to millions of years. We are currently on track to reproduce similarly strong changes within just a few centuries. 

And this makes our current situation even more dangerous, because we don’t have any true analogue in the geologic record that could tell us how the individual Earth system components will react to such a massive perturbation within this short time, and whether it might trigger any irreversible changes.

Do we know how the climate would have changed between pre-industrial times and now without greenhouse gas emissions?

Yes, we can estimate this very easily from climate model simulations. The global long-term temperature trends are controlled by external forcings. The major natural forcings are changes in the amount of solar radiation reaching the Earth and the eruption of large volcanoes.

We’ve known about these processes since pre-industrial times, and can include them in climate models to estimate their influence on surface temperatures. And while they cause some year-to-year variability, their long-term effect on the global mean temperature is virtually zero over the last 170 years. 

And even more importantly, these natural forcings are nowhere enough to explain the observed temperature trend over the last decades. Only the addition of the human-driven forcing allows the models to reproduce the measured warming of about 1°C since pre-industrial times. This is the evidence for the human influence on the global climate.

Why did you build climatearchive.org, and what do you hope to achieve with it? 

I am particularly interested in how we can share our climate model data and research findings with the wider public. Climate model simulations build the core foundation of our future warming projections, climate targets, and mitigation strategies. Even though they are among the most essential datasets for the future of our society, only a tiny fraction of the general population can directly access and evaluate them. That’s why I decided to develop climatearchive.org .

Data visualizations are a powerful tool for science communication and can make a difference at how the public sees and interacts with climate change data. I hope the easy access to climate data, even on a smartphone, can also motivate younger people and even school children to think about and discuss our past and future climate change.

Have YOU got any burning climate questions you’re dying to ask? Send us an e-mail at hi@klima.com or follow us on social and send us your questions there.