The Intergovernmental Panel on Climate Change (IPCC) has said in a new assessment report that limiting global warming to 1.5° C would require rapid, far-reaching and unprecedented changes in all aspects of society. The Special Report on Global Warming of 1.5° C was released today at Incheon, South Korea and will be a key scientific input into the Katowice Climate Change Conference in Poland in December, when governments review the Paris Agreement to tackle climate change.
The report’s full name 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.’ Ninety-one authors and review editors from 40 countries prepared the IPCC report in response to an invitation from the United Nations Framework Convention on Climate Change (UNFCCC) when it adopted the Paris Agreement in 2015.
The report highlights a number of climate change impacts that could be avoided by limiting global warming to 1.5° C compared to 2° C, or more. For instance, by 2100, global sea level rise would be 10 cm lower with global warming of 1.5° C compared with 2° C. The likelihood of an Arctic Ocean free of sea ice in summer would be once per century with global warming of 1.5°C, compared with at least once per decade with 2° C. Coral reefs would decline by 70-90 percent with global warming of 1.5°C, whereas over 99 percent would be lost with 2° C.
Limiting global warming would also give people and ecosystems more room to adapt and remain below relevant risk thresholds. The report also examines pathways available to limit warming to 1.5° C, what it would take to achieve them and what the consequences could be. “The good news is that some of the kinds of actions that would be needed to limit global warming to 1.5° C are already underway around the world, but they would need to accelerate,” said Valerie Masson-Delmotte, Co-Chair of Working Group I.
The report finds that limiting global warming to 1.5° C would require “rapid and far-reaching” transitions in land, energy, industry, buildings, transport, and cities. 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. This means that any remaining emissions would need to be balanced by removing CO2 from the air.
It is evident that rapid action is essential and the next ten years will be crucial. If the planet continues to warm at the current rate of 0.2℃ per decade, the 1.5° C threshold will be reached around 2040. At current emissions rates, there is a high probability that we will have used up our entire carbon budget for limiting warming to 1.5° C within the next 10 to 14 years.
The IPCC is the leading world body for assessing the science related to climate change, its impacts and potential future risks, and possible response options. The report was prepared under the scientific leadership of all three IPCC working groups. Working Group I assesses the physical science basis of climate change; Working Group II addresses impacts, adaptation and vulnerability; and Working Group III deals with the mitigation of climate change.
The report also finds that, in the likelihood that governments fail to avert 1.5° C degrees of warming, the world could overshoot that target, and then work to bring it back down through a combination of lowering emissions and deploying carbon capture technology. In such a scenario, some damage would be irreversible, the report found, including the total die-off of coral reefs. However, the sea ice that would disappear in the hotter scenario would return once temperatures had cooled off.
The Paris Agreement adopted by 195 nations at the 21st Conference of the Parties to the UNFCCC in December 2015 included the aim of strengthening the global response to the threat of climate change by “holding the increase in the global average temperature to well below 2°C above preindustrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels.”
As part of the decision to adopt the Paris Agreement, the IPCC was invited to produce, in 2018, a Special Report on global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways. The IPCC accepted the invitation, adding that the Special Report would look at these issues in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty.
Global Warming of 1.5° C is the first in a series of Special Reports to be produced in the IPCC’s Sixth Assessment Cycle. Next year the IPCC will release the Special Report on the Ocean and Cryosphere in a Changing Climate, and Climate Change and Land, which looks at how climate change affects land use.
The landmark report from the United Nations’ scientific panel on climate change paints a dire picture of the immediate consequences of climate change, far worse than previously thought. The authors of the report stated that avoiding the most serious damage requires transforming the world economy within just a few years. But while they conclude that it is technically possible to achieve the rapid changes required to avoid 1.5° C degrees of warming, they concede that it may be politically unlikely.