Interview with climate researcher: “Every tenth of a degree makes a difference”

The climate report proves that climate change is man-made, says researcher Friederike Otto im tagesschau24-Interview. The extent to which warming can still be limited also depends on future decisions and activities.

tagesschau24: Ms. Otto, in your opinion, what are the most important results of this current report by the Intergovernmental Panel on Climate Change?

Friederike Otto: It is a very important report – there is absolutely no question about it. That climate change is man-made, that the effects of climate change can already be felt all over the world. In every region of the world, climate change has changed events in their probability and intensity extremely. But it will also depend on our decisions and our activities whether we can limit warming. Because the report also clearly states that it is still possible if we rapidly and sustainably reduce emissions in the next few years – especially CO2 emissions. That we can then limit the warming to 1.5 degrees and thus stop many of these changes in an area that we can still handle.

tagesschau24: The results of many thousands of studies have been brought together for this report. Where and how is climate change noticeable? Are there any new findings?

Otto: In contrast to the last report, this report has much more information on regional climate change and, above all, on extreme events. For example, heat waves have become much more likely and intense all over the world. So that is one of the very noticeable consequences of climate change.

This also applies to heavy rain events in many parts of the world – but the change is somewhat smaller there. In areas of the world that are already prone to drought, droughts have also increased significantly. And then of course there are the longer-term changes, such as the rise in sea levels. We do not yet see the rise in sea level associated with the current temperatures because the ocean is a slowly reacting system. So we will see even more sea level rise over decades and centuries. And the same applies to glaciers.

tagesschau24: Are there regions anywhere in the world that have not yet been affected by climate change?

Otto: No, the report shows that very clearly. All regions of the world have felt changes due to climate change. There is no region that is not affected.

Dramatic effects from tilting the tipping points

tagesschau24: In climate research, one works with the concept of tipping points. What does it mean? And where are we at the moment?

Otto: Tipping points are elements of the climate system that can change abruptly and thus have irreversible and large-scale consequences in the entire climate system. An example that has just been in the media in the past few days is the meridional circulation in the Atlantic – also known colloquially as the Gulf Stream. Theoretical studies have shown that it has two states. One state is the one we know now. But the circulation can also break off and run completely differently, which would have great, dramatic effects on the weather in Europe. The death of the Amazon rainforest would be another example.

The bad news is that we cannot rule out the possibility that some of these tipping points have already tilted – or even with slight future warming such as 1.5 or two degrees that they are triggered to tip over into this other state. But the likelihood of this is very low at the moment.

But with higher warming the probability increases dramatically that such tipping points can tip. In this respect, this is also a very important point that must be taken into account in the risk assessment: the higher the global mean temperature rises, the less we can rule out that such tipping points can tip over.

tagesschau24: Based on the new data, one can also look further into the future. What developments can already be foreseen? Can you give examples?

Otto: For one thing, sea levels will continue to rise over the next decades and centuries, even if we limit temperatures to 1.5 or two degrees. The same applies to the melting of the glaciers and to some extent also to the thawing of the permafrost. Extreme weather events such as heat waves, heavy rain events and droughts will also continue to increase. Every tenth of a degree, every bit of emission really makes a difference – especially when it comes to heat waves.

tagesschau24: On the role of humans – can it be proven to what extent we negatively influence the climate through our dealings with nature?

Otto: This progress report says very clearly: It is a fact that the earth has warmed and that the reason for this is the burning of fossil fuels. It is man-made, there is no longer any doubt about it. And that also means that many of these changes that we see at regional levels and in extreme events can be traced back to man-made climate change. The so-called assignment research examines the observed changes: What are the causes? What part of this change is based on greenhouse gases? What proportion is perhaps caused by aerosol pollution or changes in land use – or also by the natural variability of climate change? Research in this area has made incredible strides over the past eight years and this is reflected in this report.

“The 1.5-degree target is physically absolutely possible”

tagesschau24: The Paris climate agreement aims to limit global warming to two degrees. In your opinion, can that still be achieved?

Otto: The Paris climate agreement also speaks of 1.5 degrees. And this report shows very clearly that we can still achieve that. Because if we bring greenhouse gas emissions to net zero by the middle of this century, then we can meet the 1.5 degree target. So physically it is absolutely possible. But of course it means that we now have to undertake rapid and sustainable emissions reductions globally and immediately.

tagesschau24: The Intergovernmental Panel on Climate Change is politically independent. What role can the report play as a basis for policy decisions?

Otto: This report is also politically relevant. That means, on the one hand, the information is important in order to know: How has climate change changed in all regions of the world today? What will happen in the next few years, decades? This is important information for customization. And then, of course, what is the remaining budget of emissions that we can still emit in order to meet the 1.5-degree target or the two-degree target from the Paris Agreement?