Why is global warming above 1.5 °C a problem? [2/3]

Comments and technical notes

• Full texts from infographics, detailed citations and links to sources that served as background can be found in the table of our processed data.
• A basic overview of tipping points is provided by the 2008 article Tipping elements in Earth’s climate system (including a more detailed discussion of the mathematical aspects of tipping points). For a clearer understanding of the dynamic behaviour of individual systems, it is advisable to read the articles to which this summary article refers or to which other compilation studies (e.g., IPCC SR15) refer.
• We can find a detailed explanation of the meaning of the 1.5 °C limits, a discussion of the different impacts of warming of 1.5 °C, 2 °C, and more in the third chapter of the 2018 IPCC SR15 report. The report further states that radical reductions in greenhouse gas emissions avoid temperature increases above 1.5 °C relative to pre-industrial levels. However, it also argues that existing national commitments under the Paris Agreement are insufficient to achieve even the 2 °C target.
• The full quote from the Paris Agreement reads: “This Agreement, in enhancing the implementation of the Convention, including its objective, aims to strengthen the global response to the threat of climate change, in the context of sustainable development and efforts to eradicate poverty, including by: Holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels…” (see the Paris Agreement).
• Selection of breakpoints shown. We decided to leave out some of the breakpoints presented in the articles (Marine methane clathrates, Ocean anoxia, Antarctic ozone, and Antarctic bottom water formation). We are not including these breakpoints either because of the low level of understanding of the dynamics of the given system or because more recent research shows that the system is probably more stable than predicted. On the contrary, we decided to include Heat waves and Mountain glaciers. Strictly speaking, they are not large systems (large tipping elements) because they have a significant and imaginable impact on people’s lives and ecosystems.
• We have used Wikipedia as a source for the parts of the texts that are explanatory (e.g., the extent of the taiga and the size of the Greenland ice sheet) and do not contain statements about tipping points. We chose Wikipedia in this case because it is available online, it is a single source for this type of information and, in most cases, it is well-edited.
• A tipping point is a tipping element. In English, the term tipping element means a system (cryospheric, climatic, or ecosystem) that “can break” – that is, go into a qualitatively significantly different state. The term tipping point here refers to the threshold at which this break is likely to occur (or, to be more mathematically precise, the interval of a parameter, usually temperature). For this graphic, we write about tipping points and leave the appropriate English name to linguists.

More resources on tipping points

• In November 2019, Nature published an article on tipping points and the possibility of cascading: Climate tipping points.
• The Carbon Brief’s article provides detailed explanations and commentary on each tipping point.