1. Global average temperature has already risen by around 1 °C (relative to 1850–1900) (IPCC 2013, 2018). Around half of this increase has occurred in the last 30 years (NASA 2018, IPCC 2014).
2. Globally, the years 2015, 2016, 2017 and 2018 were the hottest years since weather records began (NASA, 2019).
3. The temperature rise is almost entirely attributable to human-caused greenhouse gas emissions (U.S. Global Change Research Program 2017, IPCC 2013, 2014).
4. Even with current levels of warming, many regions are already facing more frequent and more intense extreme weather events and their consequences, such as heatwaves, droughts, wildfires and heavy precipitation (see, for example, IPCC 2012, 2013, 2018, National Academies of Sciences, Engineering, and Medicine 2016).
5. The impacts of global warming also pose a threat to human health (Watts et al., 2015, 2018). In addition to the direct consequences mentioned above, indirect effects of global warming such as food insecurity and the spread of pathogens and disease vectors must also be taken into account.
6. If the international community fails to meet the Paris Agreement's goal of limiting warming to 1.5 °C, significantly amplified climate impacts on people and nature are to be expected in many regions of the world (IPCC 2018).
7. To keep warming below 1.5 °C with a high degree of probability, greenhouse gas emissions must decrease very rapidly and, in particular, net CO2 emissions must be reduced to zero globally within the next 20 to 30 years (IPCC 2013, 2018).
Note: The above version is a minor correction to the published and signed version, which read: "To keep warming below 1.5 °C with a high degree of probability, net greenhouse gas emissions (in particular CO2) must decrease very rapidly and be reduced to zero globally within the next 20 to 30 years."
8. Instead, CO2 emissions continue to rise. With the proposals currently on the table worldwide, warming by the end of the century is likely to exceed 3 °C and subsequently increase further due to ongoing emissions and feedback effects (Climate Action Tracker 2018).
9. At current emission levels, the remaining global CO2 emissions budget for the 1.5-degree pathway will last only around 10 years. Even for the 2-degree pathway, it will only last around 25–30 years (MCC 2018, IPCC 2018).
10. After that, we will be living on a "CO2 overdraft", meaning that the greenhouse gases emitted from that point onwards will have to be removed from the atmosphere at great effort at a later stage (e.g. Rogelj et al., 2018; Gasser et al., 2015). It is the young people alive today who are expected to pay back this "debt". If this does not succeed, many future generations will suffer the severe consequences of global warming.
11. As the Earth continues to warm, dangerous climatic tipping points in the Earth system — that is, self-reinforcing processes — become increasingly likely (Schellnhuber et al., 2016; Steffen et al., 2016 and 2018). This would mean that a return to today's global temperatures would no longer be a realistic prospect for future generations.
12. The oceans are currently absorbing around 90% of the additional heat (IPCC 2013). They have also absorbed around 30% of the CO2 emitted to date. The consequences include sea level rise, loss of sea ice, ocean acidification and oxygen depletion. The consistent implementation of the Paris Agreement's goals is essential to protect people and nature and to limit the loss of marine species and habitats, particularly the acutely endangered coral reefs (IPCC 2018).
13. In many areas, the foundations of human life are being threatened by the transgression of planetary boundaries (Steffen et al., 2015; SRU, 2016). As of 2015, two of the nine boundaries have been considerably exceeded (climate warming and land-use change), while two further boundaries — the destruction of genetic diversity (biodiversity) and the disruption of phosphorus and nitrogen cycles — have been critically exceeded (Steffen et al., 2015).
14. We are currently experiencing the largest mass extinction since the age of the dinosaurs (Barnosky et al., 2011). Species are currently going extinct globally 100 to 1,000 times faster than before the onset of human influence (Ceballos et al., 2015; Pimm et al., 2014). Over the last 500 years, more than 300 terrestrial vertebrate species have gone extinct (Dirzo et al., 2014); the studied populations of vertebrate species declined by an average of 60% between 1970 and 2014 (WWF 2018).
15. The reasons for the decline in biodiversity include habitat loss due to agriculture, deforestation and land consumption for settlement and transport. Further causes are invasive species and overexploitation in the form of over-harvesting, overfishing and overhunting (Hoffmann et al., 2010).
16. Global warming adds to this: if CO2 emissions remain unchanged, up to half of all animal and plant species could disappear by 2100 from regions such as the Amazon basin or the Galápagos Islands (Warren et al., 2018). Ocean warming is also the primary threat factor for tropical coral reefs (Hughes et al., 2017 and 2018; IPCC 2018).
17. The loss of agricultural land and soil fertility, as well as the irreversible destruction of biodiversity and ecosystems, also endanger the livelihoods and options for action of both present and future generations (IPBES 2018a and 2018b; Secretariat of the CBD, 2014; Willett et al., 2019; IAAST 2009a and 2009b).
18. Taken together, inadequate protection of soils, oceans, freshwater resources and biodiversity — combined with global warming acting as a "risk multiplier" (Johnstone and Mazo, 2011) — poses the risk that shortages of drinking water and food in many countries will trigger or exacerbate social and military conflicts and contribute to the migration of large population groups (Levy et al., 2017; World Bank Group 2018; Solow, 2013).
19. A sustainable diet involving a significant reduction in our consumption of fish, meat and dairy products, along with a reorientation of agriculture towards resource-efficient food production, is necessary for the protection of the climate and of land and marine ecosystems (Springmann et al., 2018).
20. Livestock farming produces less than one fifth of the calories consumed worldwide on more than four fifths of the world's agricultural land (Poore and Nemecek, 2018) and accounts for a significant share of harmful greenhouse gas emissions (FAO 2013). Since agricultural land includes permanent grassland, permanent crops and arable land, and a considerable proportion of permanent grassland cannot be converted into arable land, the following comparison is also relevant: over one third of the world's grain harvest is currently used as animal feed (FAO 2017).
21. Increasing the direct consumption of plant-based food reduces the demand for scarce arable land, generates fewer greenhouse gases and also offers considerable health benefits (Springmann et al., 2016).
22. Direct government subsidies for fossil fuels amount to several hundred billion US dollars per year (Jakob et al., 2015). When the social and environmental costs not offset by taxes (primarily healthcare costs due to air pollution) are also taken into account, the use of fossil fuels is estimated by International Monetary Fund (IMF) experts to be subsidised globally at around 5 trillion US dollars per year — equivalent to 6.5% of the world's gross domestic product in 2014 (Coady et al., 2017).
23. To give effect to the polluter-pays principle, climate damage costs would need to be factored into the price of burning fossil fuels. One method that can reduce emissions particularly efficiently is, for example, CO2 pricing. As long as a supply based on affordable renewable energy sources has not yet been sufficiently achieved, the resulting burdens must be designed to be socially equitable. This can be done, for example, through transfer payments or tax relief for particularly affected households, or through a flat-rate payment to citizens (Klenert et al., 2018).
24. Sharply falling costs and rising production capacities for established climate-friendly technologies are making a shift away from fossil fuels towards an energy system based entirely on renewable energy affordable and are creating new economic opportunities (Nykvist and Nilsson, 2015; Creutzig et al., 2017; Jacobson et al., 2018; Teske et al., 2018; Breyer et al., 2018; Löffler et al., 2017; Pursiheimo et al., 2019).
Here you'll find the facts including sources as a PDF