2 degree climate target

The two degree target is the international climate policy goal of limiting global warming to less than two degrees Celsius compared to pre-industrialization levels (1850–1900). It is an integral part of the Paris climate agreement.^[1] This objective is a political determination based on scientific knowledge concerning the probable consequences of global warming, which dates from the Copenhagen Conference in 2009.^[2] Physical climate risk scenarios, which often project to the end of the century, 2100, use the 2 °C target as a reference point. The time at which global mean temperature is predicted to reach +2 °C compared to the pre-industrial period (1850–1900) is termed the "crossing year".^[3]

Emission trajectories needed to achieve the Paris Agreement's two-degree target without negative emissions, depending on the emission peak.

Evolution of land and sea temperatures 1880-2020 compared to the 1951-1980 average.

As a global target for limiting emissions, the 2 °C target has frequently been criticized for being higher than desirable,^[1][4] because two degrees of warming will have serious consequences for humans and the environment.^[5] The IPCC Special Report on Global Warming of 1.5 °C (2018) included detailed analysis of the probable differences in impact of "limiting global warming to 1.5 °C compared with 2 °C", warning that a 2 °C temperature increase would worsen impacts that include extreme weather, Arctic sea ice decline, rising sea levels, coral bleaching, and ecosystem loss.^[6]

The impact of climate change is not uniform:^[7] for example, land regions tend to warm faster than ocean regions.^[6] NASA has modeled predicted changes in six key climate variables: air temperature, precipitation, relative humidity, wind speed, and short- and longwave solar radiation, with particular attention to their impacts on heat stress and fire weather. NASA's NEX-GDDP-CMIP6 data set models impact at a fine-grained spatial scale, which can be used to identify key risk areas and develop adaptation and mitigation action plans for specific regions. Above the 2 °C threshold, dangerous and cascading effects are predicted to occur, with many areas experiencing simultaneous multiple impacts due to climate change.^[7][8]

As of 2022, the UN Environment Programme reported that countries have not met their climate goals to date. As a result the UN Framework Convention on Climate Change predicts a likely increase between 2.1 °C and 2.9 °C in temperature by 2100, exceeding the 2 °C climate target.^[9] Some scientists suggest that the development of decarbonization technologies may offer a way to reverse the accumulation of CO2 in the atmosphere. Even if temperatures increase above 2 °C, it may become possible to halt or reverse increases by late in the century and bring CO2 levels back to the levels identified by the Paris climate agreement.^[3] This type of scenario is referred to as an "overshoot pathway".^[6] Achieving such an outcome will require multigenerational management over many decades.^[3]

See also

• Anthropocene
• Climate target
• Keeling Curve
• Eco-sufficiency

References

1. Damian, Michel (18 May 2016). "Limiter le réchauffement de la planète à 1,5 °C ? La question qui brûle" [Limit global warming to 1.5 °C? The burning question]. The Conversation (in French). Retrieved 22 August 2018..
2. Report of the Conference of the Parties on its fifteenth session, held in Copenhagen from 7 to 19 December 2009 (PDF) (Report). United Nations Framework Convention on Climate Change. 30 March 2010. Retrieved 9 November 2022.
3. Hannah, L.; Midgley, G.F. (13 November 2023). "30×30 for Climate: The History and Future of Climate Change–Integrated Conservation Strategies". Annual Review of Environment and Resources. 48 (1): 1–24. doi:10.1146/annurev-environ-112321-114023. ISSN 1543-5938. Retrieved 27 November 2023.
4. Pérez, Eddy (13 August 2021). "Climat : le rapport du GIEC est bouleversant. Il est maintenant temps d'agir" [Climate: the IPCC report is shocking. Now is the time to act]. The Conversation (in French). Retrieved 22 August 2022..
5. Roberts, David (19 January 2018). "This graphic explains why 2 degrees of global warming will be way worse than 1.5". Vox. Retrieved 27 November 2023.
6. IPCC (2018). Global Warming of 1.5 °C: IPCC Special Report on impacts of global warming of 1.5 °C above pre-industrial levels in context of strengthening response to climate change, sustainable development, and efforts to eradicate poverty (1 ed.). Cambridge University Press. doi:10.1017/9781009157940.001. ISBN 978-1-009-15794-0.
7. "NASA Study Reveals Compounding Climate Risks at Two Degrees of Warming". Climate Change: Vital Signs of the Planet. August 14, 2023.
8. Park, Taejin; Hashimoto, Hirofumi; Wang, Weile; Thrasher, Bridget; Michaelis, Andrew R.; Lee, Tsengdar; Brosnan, Ian G.; Nemani, Ramakrishna R. (May 2023). "What Does Global Land Climate Look Like at 2 °C Warming?". Earth's Future. 11 (5). doi:10.1029/2022EF003330. ISSN 2328-4277.
9. Hodgson, Camilla (October 27, 2022). "Climate graphic of the week: World on track for up to 2.6C temperature rise by 2100, reports UN". The Financial Times Limited.