“There is still a chance for us to limit human-caused global warming“

Astmospohere research Professor Joachim Curtius from the faculty of Geosciences / Geography at Goethe University (Credit: Dettmar)

Joachim Curtius has been professor for experimental atmospheric research at Goethe University since 2007, and heads the Institute for Atmosphere and Environment. The renowned researcher is among the most-cited scientists at Goethe University and was elected “Scientist of the Year“ in 2017. “Goethe-Uni Online” talked to him about the report from the Intergovernmental Panel on Climate Change (IPCC) from August 8.

With the concentrated expertise of 107 scientists, the IPCC in Geneva issued an urgent appeal to global politics to work toward lifestyle changes, particularly in industrialised countries. The dramatic rise in global temperatures plays a decisive role in the analysis. As atmosphere researcher, what consequences do you draw from the report?

 The new IPCC report is particularly concerned with the interdependence between climate change and land surfaces, especially forests and agricultural areas. An important aspect is the role played by moors. Moors that have been drained by humans emit enormous amounts of CO2 into the atmosphere over a long period, amounting to almost 5 percent of total emissions in Germany. By stopping peat extraction, rewetting drained areas and renaturalising, these emissions could be avoided, and a lot could also be accomplished to improve biodiversity.

The second point in this report is that agriculture is a significant cause of climate change on the one hand, but is also greatly harmed by it. About a quarter of all global greenhouse emissions come from agricultural and forest operations. In particular, the non- CO2 greenhouse gases such as methane from cattle and rice cultivation, or laughing gas from fertilizers, come from agriculture. At the same time, increasing heat waves, droughts, torrential rainfall and many other factors of climate change will have an enormous impact on agricultural yields. 

And how does it look for forests?

That’s the third issue. It will be very difficult and costly to adjust our forest to the quickly changing conditions caused by climate change over the next hundred years: the significant damages we are seeing from drought and bark beetle infestation make the problem absolutely clear. A much greater problem, however, is the fire clearing of the tropical rain forests. This leads to several million tons of CO2 being released into the atmosphere every year. The resulting open space is used in Brazil for cattle farming and soy cultivation, with the primary use of soy being feed for livestock in industrialised countries. The report also reveals that more than 80 percent of agricultural land worldwide is used for livestock and cultivation of feed for animals. If we significantly reduce our meat consumption, large areas could be reforested and renaturalised.

What are the consequences for our diet?

The report actually makes clear demands for a change in lifestyle and diet in industrialised countries. We also need to stop throwing away so much food. Throwing away currently about 30 percent of our groceries in Europe is an enormous waste of resources and unnecessary emissions for production. To paint a picture: with regard to meat, this means many millions of cattle, pigs and chicken are being raised for the garbage can, often in conditions that are ethically extremely questionable.

Reading the report, one could come to the conclusion that the process of global warming is already farther along than had been thought possible just a few years ago. How do you explain this enormous acceleration?

No, global warming is not actually farther along than the calculation models predicted several years ago. In many aspects, what is happening is precisely what the climate models predicted years ago, but what this actually means is now slowly dawning on a wider public. And climate researchers are able to provide increasingly more detail, not only on the changes to global averages, but to regional changes, changes in weather extremes, and the many consequences for humans, nature and the environment. The extremes in this decade also lie beyond previous natural fluctuations for the first time: the constantly new record temperatures or the rise in average summer temperatures in Europe are good examples. This makes it clear for the first time that we are not talking about predictions for a distant future that may or may not come about. Climate change has already made its many consequences directly perceptible even here in our more moderate climate zones. Concurrently, the time that remains for us to act is growing shorter. Some changes are actually accelerating, but this is mostly due to continually increasing emissions.  

Is there a point at which climate change becomes irreversible? Has this point already been reached? Or is there still a chance of limiting human-caused warming?

Yes, there are certainly tipping points at which a climate system quickly slides into a totally new regime. With continued strong warming and continued fire clearing of the Amazon rain forest, it’s possible that a point will be reached at which the evaporation from the forests, and with it the precipitation and temperatures in this region, change so suddenly that the remaining forest can no longer survive, and these changes prove to be irreversible. It is, however, very difficult to estimate exactly when such a point might be reached.

Changes caused by climate change are probably already irreversible in some areas. For example, the Artic Sea’s expansion dramatically decreased in the summer and before the century is over it will probably completely vanish each summer. Or consider the coral reefs: when the corals die off, they will be gone forever.

Do you think there is a danger that many people will come to the conclusion that changing their consumer behaviour would be pointless and ineffective?

In my opinion, the changes are dramatic, but a point has not been reached where the problems are so huge that we can’t do anything about them. There’s definitely still a chance of limiting human-caused warming so that catastrophic damages can be avoided if we – especially the industrialised countries who are primarily responsible – act quickly and decisively.

It is certainly not too late to change our consumer behaviour. Of course, we not only need to achieve a reduction in emissions in Germany and Europe; the US, China, Brazil and other countries have to be persuaded to go along. But certainly the first step is for everyone to sweep in front of their own door. For over a century we have essentially caused the emissions and built our wealth on them, so that we have a great responsibility to be the first to reduce them. I don’t think that the necessary changes can be accomplished by voluntary conservation, however – we need rules and laws that apply to everyone. It’s just like taxation: Every country has laws and everyone has to contribute. If taxes were paid on a voluntary basis, by appeal, tax income would only be a fraction of what it is. But tax income is crucial to finance education and the many other tasks of the state. I think we have reached a point where the democratic majority in this country sees the necessity of regulations to reduce emissions and expects government to introduce these regulations quickly, efficiently, and bindingly for all.

In the event that a radical change in global CO2 emissions is possible: are there findings regarding the timeframe in which the warming trend can still be stopped or even reversed?There are meanwhile many calculation models for precisely this question. We assume that it’s  possible to stop the warming trend at maximal 1.5 to 2 degrees and over the long term, and even reverse it if global CO2 emissions are immediately and continually reduced and even reach “net zero“ between 2040 and 2055. Climate neutrality could be achieved if fossil emissions into the atmosphere are reduced to a small fraction of current levels and the remaining emissions of CO2, methane, and laughing gas are compensated by measures that remove CO2 from the atmosphere, such as afforestation and “BECCS” – extracting bioenergy from plants and capturing and storing the carbon. There are now also many studies showing how global energy needs can be met completely by solar and wind energy by 2050, what this transformation would cost, and what options are available to remove CO2 from the atmosphere.  

What does this mean for Germany’s energy transformation?

The energy transformation that is necessary globally is certainly much more radical than what has already been introduced in Germany over the past years. In the last 30 years in Germany, we have only managed to reduce emissions by about 1 percent per year, but 4 percent per year will be necessary in the coming 25 years. That’s very ambitious and needs to be started right away. But I consider it to be absolutely achievable without having to fear an “eco”-dictatorship or something similar. We have to accept that we cannot continue to live at the expense of the environment, at the expense of the poorest countries, and at the expense of future generations. It is as if we are continually taking out uncovered loans and blowing the money even though these loans will have to be paid back at horrendous interest rates by the next generation and those countries hit the hardest. CO2-intensve products and services should be correspondingly expensive. Flying is extremely harmful for the climate and I see no reason why kerosene should not be taxed as highly as diesel and petrol, for example. The most important thing, however, is that we switch, quickly and completely, to regenerative energies and greatly improved energy efficiency in all sectors. As long as our energy supply relies to 80 % on fossil fuels, we are unfortunately still miles away from sustainability.

How strong do you consider the options for countering climate change with technological measures?

That depends on what you mean by “technological measures” exactly: On the one hand, solar and wind energy are meanwhile so well developed that they could basically cover global energy supply. Techniques such as storage techniques, and the “power-to-liquid-transformation“ technique for synthetic airplane fuel still require significant technological development in the future, but they are feasible. The technologies for separating CO2 in coal power plants and then storing it underground will probably also be used in some countries such as China or Russia in the future. Technologies to remove CO2 from the atmosphere will certainly also be researched and developed, but we shouldn’t put too much hope in this solving all our problems in the future. I am very sceptical with regard to technologies that actively influence the climate, for example introducing particles into the stratosphere – that is like driving out the devils by Beelzebub instead of tackling the causes.

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