1.5 degree goal

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The 1.5 degree target is understood to mean the goal of limiting the man-made global temperature increase due to the greenhouse effect to 1.5 degrees Celsius . According to a special report by the Intergovernmental Panel on Climate Change , the 1.5 degree target has clear advantages over the 2 degree target . Almost all countries in the world have signed a treaty with the Paris Agreement, according to which they want to make efforts to achieve the 1.5 degree target.

reachability

In a 2017 study, the chances of reaching the 1.5 degree target were rated as low. At the time, it was assumed that even without further greenhouse gas emissions, the global average temperature would rise to at least 1.1 degrees Celsius compared to the pre-industrial era, and with a probability of 13% even to 1.5 ° C or more. A second study from the same year considers even limiting global warming to 2 degrees by 2100 to be unlikely, let alone 1.5 degrees. According to the models at the time, which relied on predictions about the gross domestic product per inhabitant and population development, the probability of achieving this goal was estimated at just one percent.

However, the special report of 1.5 ° C global warming by the Intergovernmental Panel on Climate Change published in October 2018 comes to the conclusion that the 1.5 degree target can still be achieved. For this to happen, mankind's CO 2 emissions would have to begin to decline significantly long before 2030 and reach zero net emissions by around 2050. In order to reduce greenhouse gas emissions in this relatively short period of time, a shift away from fossil fuels towards renewable energy sources and from a meat-based to a predominantly plant-based diet is required . At the same time, sustained negative emissions of 100 to 1,000 billion tons of CO 2 are required by the end of the century, which corresponds to 2.5 to 25 times the annual CO 2 emissions of around 40 gigatons . One way of doing this naturally is carbon dioxide removal measures (CDR) in connection with agriculture, forestry and other land use (AFOLU) such as afforestation or mire rewetting , but this is not sufficient in most of the modeled emission paths of the IPCC. The separation and storage of carbon dioxide would also have to be used to cool the earth down again after it has exceeded the 1.5 degree mark. The Intergovernmental Panel on Climate Change itself writes that "it has not yet been confirmed that such technologies work on a large scale".

advantages

The IPCC special report on 1.5 ° C global warming hits a. The following key statements on the consequences of global warming of 1.5 ° C compared to those of global warming of 2 ° C:

  1. A less pronounced increase in average temperatures , heat extremes , droughts , heavy precipitation and precipitation deficits.
  2. The sea ​​level would rise 0.1 meters less when the 1.5 degree target is reached than when the 2 degree target is reached. Based on the population figures from 2010 and without adaptation measures, up to 10 million more people would be affected by the rise in sea levels if the temperature rose by 2 ° . Even after this century it will continue to rise even if the 1.5-degree target is met, but at a slower rate than with 2 ° C global warming.
  3. Fewer species would become extinct , the damage to ecosystems on land, in freshwater and on coasts would be less, so that more of their ecosystem services would be preserved.
  4. Less warming and acidification of the oceans with a smaller decline in the oxygen content in the sea and, associated with this, a smaller decline in biodiversity and fisheries yields . Statistically speaking, a summer without sea ​​ice in the Arctic would only occur once a century instead of once a decade.
  5. Lower risks to human health and safety, livelihoods, food and water supplies, and economic growth .
  6. Fewer adjustments to the new climate would be necessary. The limits of the adaptive capacity of some human and natural systems are reached at 1.5 degrees global warming, but the losses from exceeding the limits of adaptation to climate change are lower than at 2 degrees global warming.

The risk of triggering tipping elements and uncontrollable chain reactions is significantly lower at a temperature of 1.5 ° C. Tilting elements of the cryosphere could already be dangerously close, according to a number of researchers in a comment published in 2019. If the temperature rises by 1.5 ° C to 2 ° C, the Greenland ice sheet or the Arctic sea ​​ice could melt. The tipping point for the West Antarctic Ice Sheet could already be exceeded today, but a warming of 1.5 ° C would slow down the melting process by a factor of ten compared to 2 ° C global warming and make it easier to adapt to a sharply rising sea level. Possibly the CO 2 budget of 500 billion tons for a 50 percent chance of reaching the 1.5 degree target has already been used up.

Individual evidence

  1. ^ The international climate treaty - without the USA. In: br.de. November 5, 2019, accessed January 27, 2020 .
  2. ↑ climate agreement in Paris. Swiss Federal Council, July 30, 2019, accessed on January 27, 2020 ( Swiss Standard German ).
  3. ^ Paris Agreement. (PDF) German Federal Environment Agency, June 14, 2016, accessed on January 27, 2020 .
  4. ↑ Marlene Weiß: You can forget the 1.5 degree goal. In: sueddeutsche.de. August 1, 2017, accessed December 31, 2019 .
  5. ↑ Less than 2 ° C warming by 2100 unlikely. In: nature.com. July 31, 2017, accessed December 30, 2019 .
  6. ↑ a b c 1.5 ° C Global Warming - Summary for Policy Makers. In: de-ipcc.de. German IPCC coordination office, accessed on December 31, 2019 .
  7. ↑ Joachim Müller-Jung: Report of the Intergovernmental Panel on Climate Change: The climate thorn in the meat. In: faz.net. August 8, 2019, accessed December 31, 2019 .
  8. ↑ Annika Flatley: Study: Vegan diet could save the climate and human lives. In: utopia.de. April 1, 2016, accessed January 9, 2020 .
  9. ↑ Kati Mattern, Eric Fee, Thomas Voigt, Juliane Berger, Guido Knoche, Achim Daschkeit, Claudia Kabel, Mathias Bornschein: Key messages of the IPCC special report on 1.5 ° C global warming for dissemination to the public. (PDF) German Federal Environment Agency, October 2, 2019, accessed on January 9, 2020 .
  10. ↑ How the 1.5 degree goal can be achieved. In: orf.at. March 5, 2018, accessed December 31, 2019 .
  11. ↑ 1.5 ° C Global Warming - Frequently Asked Questions and Answers. In: de-ipcc.de. German IPCC coordination office, accessed on December 31, 2019 .
  12. ↑ Timothy M. Lenton , Johan Rockström , Owen Gaffney, Stefan Rahmstorf , Katherine Richardson , Will Steffen , Hans Joachim Schellnhuber : Climate tipping points - too risky to bet against . In: Nature . November 27, 2019, doi : 10.1038 / d41586-019-03595-0 (Open Access).