No getting around the massive CO2 reduction

In the run-up to the new world climate report, experts make it clear, in view of the current state of research, that there is no way around a rapid and consistent reduction in CO2 emissions. Politicians and industry must act urgently.

26.07.2021 - Actionism and short-term symptom treatment after catastrophes, instead of acting precautionary and thus sustainable - this seems to be the way of current politics. It was not 40 years of anti-nuclear movement that ultimately caused the shutdown of nuclear power plants in Germany, but a nuclear GAU in Fukushima, which made the associated suffering and destruction visible in terrible images worldwide. Now it is the images of the flood disaster in western Germany that are disturbing, and once again call climate policy into question.

The galloping climate change
"The effects of climate change are showing up all over the world. Also in Germany, where just last week a heavy rain disaster hit North Rhine-Westphalia and Rhineland-Palatinate on an unprecedented scale," warned Professor Astrid Kiendler-Scharr during the press briefing in Berlin on the upcoming report of the Intergovernmental Panel on Climate Change (IPCC) at the German Climate Consortium (DKK). "Such extreme weather events and their devastating consequences for us humans have already become more likely with climate change. They are a reminder to us to really implement the climate targets now and not get involved in galloping climate change."

The atmospheric scientist works at Forschungszentrum Jülich and is chair of the board of the Scientific Association of Climate Research Institutions. She anticipates the decisive conclusion of the world climate report: "The new report will underpin with comprehensive results of international climate research how far-reaching and serious the consequences of man-made climate change already are."

What is the IPCC world climate report about?
By itself, a new report won't change policy - but in the context of current climate crisis-related events, it does gain renewed importance and, above all, visibility in the public eye. After all, that creates pressure, especially in an election year.

"With climate models, we can simulate how the climate on Earth could develop in the future, based on scientific laws," Professor Mojib Latif from GEOMAR Helmholtz Centre for Ocean Research Kiel explains the research work. "And we also see that what the models calculated earlier now applies very well."

The unpredictable variable in model calculations - humans
So climate models are basically very reliable, Latif says, especially related to large-scale changes. "Nevertheless, we can't make a prediction of what the climate will be like in the middle of the century. That's because it's humans who remain unpredictable. Will we manage to stop greenhouse gas emissions quickly with ambitious climate action, or will we let it continue?" Humans are still the biggest factor of uncertainty in the climate system, he said.

There is still a choice
That's why the World Climate Report fans out and scientifically evaluates various possible emissions scenarios. However, the experts do not make any recommendations for action in the report - because this remains the responsibility of politics and society in the IPCC process.

What does climate neutrality actually mean?
Global climate neutrality by the middle of the century at the latest is central to ensuring that the consequences of climate change remain reasonably manageable, the team of experts asserts. "To stop the temperature rise and reduce the risks for future generations, global greenhouse gas emissions must fall to zero in the overall balance," explained Dr. Hauke Schmidt of the Max Planck Institute for Meteorology. "So-called net zero emissions describe as a concept that the concentration of greenhouse gases in the atmosphere does not increase further."

Measures and possibilities must be exhausted, he said, and there are various paths. "This can also be achieved if unavoidable emissions from agriculture, for example, are offset with negative emissions - that is, additional sinks," Schmidt says. Examples would be reforestation or underground storage of carbon dioxide from bioenergy production. The latter is a contentious issue with diverse expert opinions.

Repeated reminder: CO2 budget is limited
The science team makes it clear once again: "Whether we achieve the goals of the Paris Agreement to limit warming to well below two degrees Celsius depends on how much more CO2 humanity emits before it reaches net zero emissions. What is clear is that the maximum amount for this - the so-called CO2 budget - is limited."

"As a climate researcher, it was important for me to work on the elaborate preparation of the report together with more than 230 colleagues from 66 countries, so that policymakers have an up-to-date and solid scientific basis for their decisions," emphasizes Kiendler-Scharr as lead author of the sixth chapter on short-lived climate pollutants.

The first volume of the Sixth Assessment Report (AR6) will be presented to the public on August 9. It summarizes the current status of the scientific basis of climate change - such as warming and its consequences for sea level, the Arctic and extreme weather. It also provides a comprehensive overview of climate projections for the future, possible emissions scenarios, and the remaining CO2 budget to meet the goals of the Paris Agreement.

Half a degree Celsius makes a big difference
The risks of climate-related impacts are projected to be higher at 2°C than at 1.5°C global warming. According to model calculations by various science teams in the Intergovernmental Panel on Climate Change, with an additional 0.5 °C of warming, hot spells will become common in most inhabited regions, heavy precipitation in several regions, or drought and precipitation deficits.

The risks of heavy precipitation are estimated to be higher at 2 °C than at 1.5 °C of global warming, especially in regions of the Northern Hemisphere, As a result of heavy precipitation, the fraction of global land area affected by flood hazards is projected to be greater at 2 °C than at 1.5 °C of global warming. 

Instability of the Antarctic marine ice sheet and/or irreversible loss of the Greenland ice sheet could result in several meters of sea level rise over hundreds to thousands of years. These instabilities would be triggered by global warming of about 1.5°C to 2°C. The extent and speed of this rise will depend on future emissions pathways, the scientists:caution.

On land, impacts on biodiversity and ecosystems, including species loss and extinctions, are expected to be smaller at 1.5 °C global warming than at 2 °C. The same is true, he said, for impacts of other biodiversity-related risks such as forest fires and the spread of invasive species.

Economic and social shifts
Poverty and deprivation in some populations are expected to increase as global warming increases; limiting global warming to 1.5°C compared with 2°C could reduce the number of people both exposed to climate-related risks and vulnerable to poverty by up to several hundred million by 2050.

Any increase in global warming would be expected to affect human health, with mainly negative consequences. Risks from some vector-borne diseases, such as malaria and dengue fever, would increase with warming from 1.5°C to 2°C, including possible shifts in their geographic range. In the Sahel, southern Africa, the Mediterranean, central Europe, and the Amazon, reductions in projected food availability would be greater with 2 °C than with 1.5 °C global warming.

Depending on future socioeconomic conditions, the scientists forecast that limiting global warming to 1.5 °C versus 2 °C could reduce the proportion of the world's population exposed to a climate change-induced increase in water stress by up to 50 percent-but with substantial variation among different regions.

Risks to global aggregate economic growth from climate change impacts would also likely be lower by the end of this century at 1.5 °C than at 2 °C. As global warming increases from 1.5°C to 2°C, risks in the energy, food, and water sectors could overlap in space and time, creating new and exacerbating hazards, exposures, and vulnerabilities that could affect a growing number of people and regions.

Recommendations do not yet make policy
The three volumes of regular Assessment Reports are the most important result of the work of the Intergovernmental Panel on Climate Change (IPCC) and have served as the basis for national and international climate policy for more than 30 years. To date, no action has been taken on the basis of these reports. But in view of the gloomy forecasts, which are confirmed by current images in the media - whether flood victims in this country or starving people in faraway Madagascar - politicians must act decisively now. Source: