Limiting global warming to 1.5°C would require 'rapid, far-reaching and unprecedented changes in all aspects of society', said the United Nations' Intergovernmental Panel on Climate Change (IPCC) on Monday in a new assessment, at the release of a special report on global warming of 1.5°C.
Nonetheless, with clear benefits to people and natural ecosystems, limiting global warming to 1.5°C compared to 2°C could go hand in hand with ensuring a more sustainable and equitable society, said the report issued in Incheon, South Korea. The report will form the key scientific input for a conference this December in Katowice, Poland where governments will review the Paris Agreement to tackle climate change.
That Paris agreement, adopted by 195 nations 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 pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels.’
Impact of warming
"One of the key messages that comes out very strongly from this report is that we are already seeing the consequences of 1°C of global warming through more extreme weather, rising sea levels and diminishing Arctic sea ice, among other changes," said IPCC working group I co-chair Panmao Zhai.
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% with global warming of 1.5°C, whereas virtually all (> 99%) would be lost with 2°C.
"Every extra bit of warming matters, especially since warming of 1.5°C or higher increases the risk associated with long-lasting or irreversible changes, such as the loss of some ecosystems," said IPCC Working Group II co-chair Hans-Otto Pörtner. Limiting global warming would also give people and ecosystems more room to adapt and remain below relevant risk thresholds, he said.
Actions under way, but need to speed up
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 co-chair of Working Group I Valerie Masson-Delmotte.
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% 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.
"Limiting warming to 1.5°C is possible within the laws of chemistry and physics but doing so would require unprecedented changes," said co-chair of IPCC Working Group III Jim Skea.
Allowing global temperature to temporarily exceed or 'overshoot' 1.5°C would mean a greater reliance on techniques that remove CO2 from the air to return global temperature to below 1.5°C by 2100. The effectiveness of such techniques are unproven at large scale and some may carry significant risks for sustainable development, the report notes.
"Limiting global warming to 1.5°C compared with 2°C would reduce challenging impacts on ecosystems, human health and well-being," said IPCC Working Group III co-chair Priyardarshi Shukla.
The decisions we make today are critical in ensuring a safe and sustainable world for everyone, both now and in the future, said co-chair of IPCC Working Group II Debra Roberts.
"This report gives policymakers and practitioners the information they need to make decisions that tackle climate change while considering local context and people's needs. The next few years are probably the most important in our history," she said.
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. It also cites some 133 contributing authors and more than 6,000 scientific references.
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. This report about global warming of 1.5°C is the first in a series. Next year, the IPCC will release two reports; one examining the effect of climate change on ocean and the cryosphere and the other climate change’s effect on land use.
More information on the special report can be found here.