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IPCC Chair Discusses Limiting Global Warming to 1.5°C

Several forthcoming reports by the Intergovernmental Panel on Climate Change examine what needs to be done to take control of our climate future.


With a United Nations climate change conference scheduled for Bonn, Germany, from 6 to 17 November, two high-level reports released this week warn about the increasing risk of climate change. In addition, the Intergovernmental Panel on Climate Change (IPCC) is working on a separate report, to be issued in 2018, about the effects of global warming at 1.5°C above preindustrial levels.

A 30 October report from the World Meteorological Organization warned that in 2016, globally averaged concentrations of carbon dioxide surged in 1 year from 400 to 403.3 parts per million, the highest level in 800,000 years. Also, a 31 October report from the United Nations (UN) sounds an alarm about the need for accelerated short-term actions and enhanced longer-term national ambitions to meet the Paris climate agreement goal of holding global warming to well below 2°C compared to preindustrial levels.

IPCC’s 1.5°C report will focus on assessing ways to limit global warming to a 1.5°C goal by the end of the century and will examine mitigation pathways, impacts on natural and human systems, global responses, and sustainable development, said IPCC chair Hoesung Lee at a 30 October forum at Resources for the Future, a nonprofit research institution in Washington, D. C. The document will be the first of three special reports IPCC plans to release over the next several years in advance of the group’s Sixth Assessment Report (AR6) in 2021 and a synthesis report in 2022.

“Earlier and more ambitious mitigation as required by 1.5° warming will yield near-term benefits in terms of reduced climate change damage and reduce the risk of temperature overshoot and its associated damages,” Lee said. “The question is how this ambitious near-term action will materialize.”

Tying Climate Change to National Priorities

In most countries, governments are addressing climate change in the context of other national priorities such as energy security and poverty alleviation, Lee said, adding that “improvements to climate policy programs need to engage these broader national priorities.”

Lee added that in most countries, national governments as well as other parties participate in climate policy and that the involvement of a diversity of parties “certainly will facilitate deep cuts in emissions that require transformation in institutions, technologies, consumption patterns, and human behavior.”

Is a 1.5°C Goal Possible?

However, the UN report released yesterday questions whether a 1.5°C goal is possible. It notes that the gap between emissions reductions that are needed and national pledges, known as Nationally Determined Contributions (NDCs), on climate action “is alarmingly high.”

IPCC chairman Hoesung Lee discussed climate change and the group’s upcoming reports on 30 October in Washington, D. C.
IPCC chairman Hoesung Lee discussed climate change and the group’s upcoming reports on 30 October in Washington, D. C. Credit: Randy Showstack

It “is clear that if the emissions gap is not closed by 2030, it is extremely unlikely that the goal of holding global warming to well below 2.0° can still be reached,” the UN report states.

The UN report also noted a confounding factor that must be addressed to help tackle the emissions gap. Most G20 countries (including the United States), which collectively generate about three quarters of global greenhouse gas emissions, require new policies and actions to even achieve their NDC pledges, according to the report.

Add into this mix the United States pledging earlier this year to formally withdraw from the Paris climate accords. Studies cited in the UN report estimate that by 2025, emissions for the United States under the Trump administration will range from 5.7 to 6.8 gigatonnes of carbon dioxide equivalent per year (GtCO2e/yr) as opposed to 5.0 to 6.6 GtCO2e/yr under Obama administration policies. Increases in emissions output, whatever the magnitude, will further set back the world’s ability to meet climate goals.

With regard to the IPCC report, Lee noted that “there is little basis for taking at this moment an optimistic or pessimistic view about the feasibility [of] a particular temperature goal.” He added, “What is relevant is to make explicit [the] assumptions behind mitigation pathways associated with temperature goals and evaluate those assumptions.”

Increasing the Understanding About 1.5°C Warming

Lee said that at the Paris climate negotiations in 2015, “there was very little scientific understanding about 1.5° warming.” He explained that the decision to prepare the special report, which the parties at the Paris climate conference had invited IPCC to undertake, “has stimulated considerable new research” about it.

Last week, lead authors of the 1.5° report met in Malmö, Sweden, to work on addressing nearly 13,000 comments on the first draft. The final draft is slated for release in October 2018 in time for a “facilitative dialogue” later that year, which will review the targets of the Paris Agreement. Two other special IPCC reports, scheduled for release in 2019, focus on the ocean and cryosphere and on land use.

Reports “Take Time”

Lee told Eos that IPCC reports “take time” because they involve repeated drafting and review to ensure quality, transparency, and objectivity but that the drafting and review processes “underpin the strength of an IPCC assessment.”

He pointed out that the most recent IPCC assessment “established, with the greatest certainty, that the climate is changing due to human activity.” Lee said that report also highlighted the widespread climate change effects already occurring, the risk of future impacts, and possible solutions to climate change that are compatible with sustainable development. “By showing that the costs and difficulty of tackling climate change rise if responses are delayed, the IPCC highlighted the urgency of action,” according to Lee.

“The job of the IPCC is to provide policy makers with a scientific assessment of climate change, its impacts and risks, and possible response options. Thus, the IPCC is policy relevant but not policy prescriptive: It does not tell governments what to do. Climate action is the responsibility of policy makers, and sound policy can be informed by robust science,” Lee told Eos.

He said that with the upcoming special reports followed by AR6 and the synthesis report, “the IPCC will provide policy makers with one or more up-to-date and policy-relevant products a year, almost every year, for the 5 years starting in 2018.” Armed with IPCC’s forthcoming reports, “policy makers will be as up to date on climate science as is possible with a rigorous scientific assessment,” he said.

—Randy Showstack (@RandyShowstack), Staff Writer

Citation: Showstack, R. (2017), IPCC chair discusses limiting global warming to 1.5°C, Eos, 98, Published on 01 November 2017.
Text © 2017. The authors. CC BY-NC-ND 3.0
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