The Special Report on Global Warming of 1.5 °C (SR15) was published by the Intergovernmental Panel on Climate Change (IPCC) on 8 October 2018. The report, approved in Incheon, South Korea, includes over 6,000 scientific references, and was prepared by 91 authors from 40 countries. In December 2015, the 2015 United Nations Climate Change Conference called for the report. The report was delivered at the United Nations' 48th session of the IPCC to "deliver the authoritative, scientific guide for governments" to deal with climate change. Its key finding is that meeting a 1.5 °C (2.7 °F) target is possible but would require "deep emissions reductions" and "rapid, far-reaching and unprecedented changes in all aspects of society". Furthermore, the report finds that "limiting global warming to 1.5 °C compared with 2 °C would reduce challenging impacts on ecosystems, human health and well-being" and that a 2 °C temperature increase would exacerbate extreme weather, rising sea levels and diminishing Arctic sea ice, coral bleaching, and loss of ecosystems, among other impacts. SR15 also has modelling that shows that, for global warming to be limited to 1.5 °C, "Global net human-caused emissions of carbon dioxide (CO2) would need to fall by about 45 percent from 2010 levels by 2030, reaching 'net zero' around 2050." The reduction of emissions by 2030 and its associated changes and challenges, including rapid decarbonisation, was a key focus on much of the reporting which was repeated through the world. When the Paris Agreement was adopted, the UNFCCC invited the Intergovernmental Panel on Climate Change to write a special report on "How can humanity prevent the global temperature rise more than 1.5 degrees above pre-industrial level". Its full title is "Global Warming of 1.5 °C, an IPCC special report on the impacts of global warming of 1.5 °C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty". The finished report summarizes the findings of scientists, showing that maintaining a temperature rise to below 1.5 °C remains possible, but only through "rapid and far-reaching transitions in energy, land, urban and infrastructure..., and industrial systems". Meeting the Paris target of 1.5 °C (2.7 °F) is possible but would require "deep emissions reductions", "rapid", "far-reaching and unprecedented changes in all aspects of society". In order to achieve the 1.5 °C target, CO2 emissions must decline by 45% (relative to 2010 levels) by 2030, reaching net zero by around 2050. Deep reductions in non-CO2 emissions (such as nitrous oxide and methane) will also be required to limit warming to 1.5 °C. Under the pledges of the countries entering the Paris Accord, a sharp rise of 3.1 to 3.7 °C is still expected to occur by 2100. Holding this rise to 1.5 °C avoids the worst effects of a rise by even 2 °C. However, a warming of even 1.5 degrees will still result in large-scale drought, famine, heat stress, species die-off, loss of entire ecosystems, and loss of habitable land, throwing more than 100 million into poverty. Effects will be most drastic in arid regions including the Middle East and the Sahel in Africa, where fresh water will remain in some areas following a 1.5 °C rise in temperatures but are expected to dry up completely if the rise reaches 2 °C.
Main statements
The report states that global warming would likely rise to 1.5 °C above pre-industrial levels (defined as being the average during 1850–1900) between 2030 and 2052 if warming continues at the 2018 rate. SR15 provides a summary of, on one hand, existing research on the impact that a warming of 1.5 °C (equivalent to 2.7 °F) would have on the planet, and on the other hand, the steps needed to limit global warming to 1.5 °C. Even assuming full implementation of conditional and unconditional Nationally Determined Contributions submitted by nations in the Paris Agreement, net emissions would increase compared to 2010, leading to a warming of about 3 °C by 2100, and more afterwards. In contrast, limiting warming below or close to 1.5 °C would require to decrease net emissions by around 45% by 2030 and reach net zero emissions by 2050 (i.e. keeping total cumulative emissions within a carbon budget). Even just for limiting global warming to below 2 °C, CO2 emissions should decline by 25% by 2030 and by 100% by 2075. Pathways (i.e. scenarios and portfolios of mitigation options) that would allow such reduction by 2050 describe a rapid transition towards producing electricity through lower-emission methods, and increasing use of electricity instead of other fuels in sectors such as transportation. On average, the pathways describing the proportion of primary energy produced by renewables as increasing to 60%, while the proportion produced by coal drops to 5% and oil to 13%. Most pathways describe a larger role for nuclear energy and carbon capture and storage, and less usage of natural gas. They also assume that other measures are simultaneously undertaken: e.g. non-CO2 emissions (such as methane, black carbon, nitrous oxide) are to be similarly reduced, energy demand is unchanged, reduced by even 30% or offsetted by an unprecedented scale of carbon dioxide removal methods yet to be developed, while new policies and research allows to improve efficiency in agriculture and industry.
Impact of 1.5 °C or 2 °C warming
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