It's our fault
Humans have changed the earth's climate; according to the new, sixth status report from the IPCC working group commissioned to review the scientific findings, there is no longer any reasonable doubt. The temperature on the earth's surface has risen by 1.1 degrees on average over the pre-industrial level, land areas warmed up by 1.6 degrees on average and oceans by 0.9 degrees. This increase has been unprecedented for at least 2000 years and arguably since the beginning of the Holocene 12,000 years ago. The last time the earth was as warm as it is today was in the Eem warm period 125,000 years ago. “The entire warming is anthropogenic,” says Karsten Haustein from the Helmholtz Center in Geesthacht. This statement is possible because the uncertainties have been significantly reduced. The warming is a consequence of greenhouse gas emissions,notes the report. Their increase since 1750 is "clearly man-made". The main driver of global warming is the greenhouse gas carbon dioxide: Its proportion in the atmosphere increased from 280 ppm (CO₂ molecules per million air molecules) to 413 ppm today. The CO₂ content in the air is higher than it has been in at least two million years.
The climate is sensitive
Andreas Frey
Freelance writer in the science of the Frankfurter Allgemeine Sonntagszeitung.
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The so-called climate sensitivity indicates how much the earth warms up when the CO₂ content in the atmosphere doubles, i.e. increases from pre-industrial 280 ppm to 560 ppm. The previous climate reports did not provide much illuminating information, in the fifth report from 2013 the researchers assumed an increase of 1.5 to 4.5 degrees with a doubling. This rather broad range has now been reduced in the sixth report. It is now expected that the temperature will rise by 2.5 to 4 degrees as a result of doubling the CO₂ content in the air. On the one hand, this is good news because Canadian climate researchers were generating horror headlines two years ago about a possible rise of 5.7 degrees; on the other hand, the 1.5-degree target that the global community agreed on in Paris will also become factual unreachable.
Extreme is the new normal
Not a single region on earth can escape climate change. Everywhere, the weather will change significantly in the years and decades to come. For the first time, the climate report therefore also deals with so-called attribution research. It is about the assignment of extreme weather conditions. Climate change is most evident in the more frequent and intense heat waves that are currently affecting the Mediterranean region. In addition, the researchers assume that extreme heat will occur more frequently in combination with drought in the future, thus reducing soil moisture. Such double blows of heat and drought are particularly dangerous because they dry up vegetation and increase the risk of fire. In a warmer world, heavy rain events and thus floods as well as the severity of cyclones will increase,which occur less frequently in terms of numbers.