The researchers have come a long way since the 2013 World Climate Report. The bottom line: The consequences of global warming are becoming increasingly clear – and the targeted climate protection is not enough.
Geneva – The Intergovernmental Panel on Climate Change presents the consequences of human-made global warming in its new report more drastically than ever before.
According to the latest scientific findings, sea level rise, ice melt, more heat waves, droughts and heavy rain can be predicted much more reliably than before. This emerges from the report on the physical basis of climate change, which was published in Geneva on Monday.
The facts are alarming: “It is very likely that episodes with heavy precipitation will become more intense and frequent in most regions with further global warming,” it says. There is also evidence that sea levels continue to rise and the ice continues to melt. “Very likely” means: with 90 to 100 percent certainty.
Even if we succeed in achieving climate neutrality by 2050, the sea level is likely to be up to 62 centimeters higher by the end of the century than in 1995-2014. Climate neutrality means that only as much greenhouse gas is emitted as sinks can absorb. “In the Arctic, three quarters of the sea ice volume has already melted in summer,” said co-author Dirk Notz from the Max Planck Institute for Meteorology. “We will probably no longer be able to prevent the Arctic Ocean from being largely ice-free in summer, at least in some years.”
The Intergovernmental Panel on Climate Change last examined the physical fundamentals in 2013. Since then, uncertainties in the climate models have been significantly reduced. Unlike then, science is now clearly stating: If greenhouse gas emissions are not reduced very quickly, the goal of limiting warming to below two degrees above pre-industrial levels will fail. In addition, more climate changes could be directly attributed to human influence, said co-author Veronika Eyring from the University of Bremen.
“There is no doubt that human influence has heated the atmosphere, ocean and land,” the report said. “Human influence has heated the climate in a way that has not happened for at least 2000 years. (…) In 2019 the CO2 concentration in the atmosphere was higher than at any other point in time for at least two million years. “
Horror developments cannot be ruled out
The Intergovernmental Panel on Climate Change also names two horror developments that are unlikely but cannot be ruled out. On the one hand, there is a rise in sea level of two meters by the end of the century, depending on how the Antarctic ice sheet continues to melt. On the other hand, there is a collapse of the Atlantic overturning current (AMOC), which has already lost momentum. It distributes cold and warm water in the Atlantic and influences the monsoons in Africa and Asia, which are important for billions of people. A collapse of the system, of which the Gulf Stream is a part, would also have an impact on Europe.
According to this report, the global mean temperature for the period 2011 to 2020 is just under 1.1 degrees above the pre-industrial level (1850-1900). According to the Paris climate agreement, the states want to keep global warming below two degrees, if possible at 1.5 degrees. “If we don’t cut emissions fast enough and reach net zero by around 2050-2070, we will miss both Paris climate targets,” said co-author Douglas Maraun from the University of Graz.
The Intergovernmental Panel on Climate Change is drafting five scenarios. Among them are two in which the world will achieve climate neutrality around 2050 and then store more CO2 than it emits. Only then could the mean temperature rise by the end of this century remain at 1.8 degrees or below.
Temperature rise of up to 5.7 degrees possible
If emissions remained the same until 2050, the temperature at the end of this century would be 2.1 to 3.5 degrees above the pre-industrial level. In two further scenarios with at least doubling of CO2 emissions by the middle of the century, an increase in temperature of up to 5.7 degrees would be possible.
“If you look at what the individual governments have pledged for climate protection, you would most likely end up in the middle scenario at the moment,” said Notz. “For the future, of course, it remains unclear whether the commitments will be kept or whether the governments will, on the other hand, intensify their efforts.”
A reality check: The US government’s energy agency (EIA) calculated in 2019 that CO2 emissions would grow from around 36 billion tons a year to more than 42 billion tons by 2050 due to the fact that many countries are just beginning to industrialize. China currently produces the most greenhouse gas, around a quarter of the total, ahead of the US with 18 and the EU with 17 percent. The proportion of CO2 emissions that are absorbed in sinks such as forests or oceans and do not remain in the atmosphere is around 44 percent, according to the report.
The report was written by more than 230 researchers from 66 countries. The summary for policy makers was unanimously approved by the 195 IPCC member countries. “So the governments are in the boat, nobody can say afterwards: I have nothing to do with it,” said Jochem Marotzke from the Max Planck Institute for Meteorology.
Although the report presents the consequences of global warming in a new drastic way, there is also good news, said the chairperson of the working group, which has viewed and assessed around 14,000 studies on climate change. Global warming could be stopped if politicians now decide on clear and immediate reductions in greenhouse gas emissions.
According to the report, the goal of keeping warming below two degrees can only be achieved with immediate and far-reaching climate protection measures. This means that climate neutrality must be achieved by around 2050-2070. Germany wants to become climate neutral by 2045.
“Unless strong and rapid reductions in emissions happen, the rise in global mean temperature since the end of the 19th century will reach or exceed 1.5 degrees in the next 20 years,” said Co-Chair Valérie Masson-Delmotte. “We hope that the information will help decision-makers and engineers to develop solutions as quickly as possible.” So far, the global mean temperature increase has been around 1.1 degrees. In Germany, according to Astrid Kiendler-Scharr from the Institute for Energy and Climate Research at Forschungszentrum Jülich, it is already 1.6 degrees.
It is now clearer than ever that practically all global warming compared to pre-industrial levels is due to human activity, said the second co-chair, Panmao Zhai. The G20, the group of the largest industrialized and emerging countries, has a special responsibility, said the head of the UN environmental program, Inger Andersen. They are responsible for 80 percent of the previous emissions. dpa
