The State of the Climate

Global surface temperature will continue to increase until at least 2050 and many of the changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia, especially changes in the ocean, ice sheets, and global sea level. From a physical science perspective, limiting human-induced global warming to a specific level requires reaching at least net-zero carbon dioxide (CO2) emissions and strong reductions in other greenhouse gas emissions.

So warns the first Working Group contribution to the Intergovernmental Panel on Climate Change’s Sixth Assessment Report. The Summary for Policymakers approved on 6 August 2021 provides a comprehensive assessment of the physical science underpinning past, present and future climate change. Many delegates underscored that the Summary for Policy Makers and the underlying report will be a key input for intergovernmental negotiations at the 26th session of the Conference of the Parties to the UN Framework Convention on Climate Change, scheduled to take place in Glasgow, Scotland, in November 2021.

As with all multilateral processes, the Intergovernmental Panel on Climate Change (IPCC) had to adjust its work amid the COVID-19 pandemic. First, authors contributing to the IPCC’s assessment report had to conduct virtual meetings to address comments received on their draft reports, then the Panel itself held its 53rd session (IPCC-53) online, first in a short procedural session and later in a resumed “53-bis” session that resulted in substantive decisions on the strategic planning schedule of the completion of the Sixth Assessment Report .

IPCC-54, however, truly broke new ground: delegates held a full-fledged virtual approval session for the Summary for Policymakers of the Working Group I contribution to the Sixth Assessment Report. The scale and ambition of the virtual decision-making process was unprecedented, not just for the IPCC, but for the UN system more broadly, as IPCC Secretary Abdalah Mokssit noted during the closing plenary. Over the course of 11 meeting days, about 300 delegates engaged in a line-by-line approval of the Working Group Summary for Policymakers. Many were skeptical that this could work, noting how challenging approval processes are even under normal circumstances, but the approval concluded as scheduled, running less than one hour past the original closing time. During the final plenary, Norway noted it was “the most well-organised approval process the Panel has ever seen” and many delegations called for using lessons learned here to inform the organization of future approval sessions.

Some of the other key messages of the Summary for Policymakers include:

• human influence has warmed the climate system;
• widespread and rapid changes in the climate have occurred;
• the scale of these recent changes is unprecedented over many centuries to many thousands of years;
• with further global warming, every region is projected to experience changes, with extremes, such as heavy precipitation, becoming greater in frequency and intensity;
• global surface temperature will continue to increase until at least the mid-century under all emissions scenarios considered;
• unless there are deep reductions in CO2 and other GHG emissions in the coming decades, 1.5°C and 2°C will be exceeded during the 21st century; and
• the effects of strong, rapid, and sustained emission reductions in terms of global surface temperature trends will begin to emerge after around 20 years.

IPCC-54, and the 14th session of Working Group I conducted under its auspices, convened virtually from 26 July to 6 August 2021.

 

A. The Current State of the Climate

A.1: This subsection addresses human influence over the climate system. Several delegates requested strengthening the language of the Headline Statement that “human influence has warmed the climate system, and widespread and rapid changes in climate have occurred.” LUXEMBOURG, supported by the NETHERLANDS, FRANCE, the UK, SAINT KITTS AND NEVIS, JAMAICA, IRELAND, and others, but opposed by SAUDI ARABIA, CHINA, and INDIA, proposed stating “observed warming of the climate system is unequivocally caused by human influence” to replace “human influence has warmed the climate system.” Some suggested also specifying the parts of the climate that are experiencing changes. The authors proposed “it is unequivocal that human influence has warmed the climate system” and “widespread and rapid changes in the ocean, atmosphere, cryosphere, and biosphere have occurred.” During further discussions, these two statements were modified to “human influence has unequivocally warmed the atmosphere, ocean, and land.” SAUDI ARABIA objected to “unequivocally.” Delegates noted compromise on explicit reference to warming of “atmosphere, ocean, and land,” rather than “climate system,” as these are unequivocally associated with human influence. INDIA opined that human influence has varying levels of confidence and likelihood across the three. Co-Chair Masson-Delmotte said this is a statement of fact and the authors concurred. After some discussion, SAUDI ARABIA accepted the compromise formulation with a small editorial change and the Headline Statement was approved.

On the estimated increase in global surface temperature since AR5 principally due to further warming since 2003-2012, SAINT KITTS AND NEVIS, supported by SWITZERLAND, LUXEMBOURG, the US, TRINIDAD AND TOBAGO, the UK, and GERMANY, suggested more specificity with regard to some of the changes in the temperature estimates resulting from changes in methodology rather than the result of natural warming. INDIA called for acknowledging that additional warming, not new or updated datasets, is the principal driver of increased warming estimates since AR5. Both suggestions were reflected in a footnote. The UK requested information on the current rate of warming. The authors said this was not addressed in the underlying report, but pointed to information provided visually in Figure Summary for Policymakers.1. A statement that each of the last four decades has been successively warmer than any preceding decade since 1850 was added at the beginning of the paragraph. The authors also changed the measurement of global surface temperature increase to reflect the different years now being specified, from 0.69˚C-0.95˚C between 1995-2014 to 0.85˚C-1.10˚C from 2001-2020.

SOUTH AFRICA asked for a clear definition of new terms, particularly net zero, in the glossary. SAUDI ARABIA requested removal of that term. The authors noted they followed IPCC practice in not examining assumptions, only the physical science response to scenarios based on them, in assessing the literature the modelling community has produced. They said the net-negative emissions description only applies to specific scenarios, and said they added one scenario to simulate the broadness of response choices. The US said the focus on future emissions is important and should feature more prominently in the box. BELIZE suggested reflecting the implications of COVID-19 on emissions trends. The authors said the mandate of Working Group I does not include validating the COVID-19 recovery trajectory.

The Summary for Policymakers Story

As Sweden highlighted during the meeting, “the Summary for Policymakers provides a story of the climate from the past to the future,” and this story is alarming:

• human influence has warmed the climate system;
• widespread and rapid changes in the climate have occurred;
• the scale of these recent changes is unprecedented over many centuries to many thousands of years;
• with further global warming, every region is projected to experience changes, with extremes, such as heavy precipitation, becoming greater in frequency and intensity;
• many changes due to past and future greenhouse gas (GHG) emissions are irreversible for centuries to millennia, especially changes in the ocean, ice sheets, and global sea level;
• global surface temperature will continue to increase until at least the mid-century under all emissions scenarios considered;
• unless there are deep reductions in CO2 and other greenhouse gas emissions in the coming decades, 1.5°C and 2°C will be exceeded during the 21st century;
• from a physical science perspective, limiting human-induced global warming to a specific level requires reaching at least net-zero CO2 emissions and strong reductions in other greenhouse gas emissions; and
• the effects of strong, rapid, and sustained emission reductions in terms of global surface temperature trends will begin to emerge after around 20 years.

The Summary for Policymakers Dance

The Summary for Policymakers is a well-crafted document, with the entire review and approval exercise intended to balance the objective to convey key messages in a concise manner while maintaining scientific accuracy. Yet, while full credit is due to all the government delegations, who come very-well prepared to engage with the authors on clarifying terms and bringing in a reality check on what is just too much scientific jargon for policymakers and laypeople to understand without at least a definition (equilibrium climate sensitivity, anyone?), the issues that usually take most time to resolve are of a different nature. Delegates often repeated the mandate for the Summary for Policymakers is to be “policy relevant, not policy prescriptive.” Yet what this means to different countries and stakeholders varies greatly—and here lies the crux of many of the lengthier debates that arose during the approval process.

Looking Ahead

For a time, it seemed the COVID-19 pandemic might put a damper on the finalisation of the Working Group I contribution. But with this approval process completed, authors and delegates succeeded in limiting delays in the timeline for completing the AR6. Sticking to the anticipated timeline is key to ensuring the AR6 informs the global stocktake established under the Paris Agreement, which aims to assess the world’s collective progress towards achieving the Agreement’s objective and long-term goals, and is scheduled to take place in 2022-2023. The IPCC had already adjusted its mode of work after the onset of the pandemic in 2020, and this meeting demonstrated that a virtual Summary for Policymakers approval can be done when needed. A seasoned delegate, however, cautioned that compared to the other Working Groups, “this was the easiest one,” noting virtual approvals of the remaining Summaries for Policymakers will likely be even more draining.

The next big milestone on the climate agenda is of course the 26th session of the Conference of the Parties (COP) of the United Nations Framework Convention on Climate Change (UNFCCC), scheduled to take place in November 2021 in Glasgow, Scotland. This IPCC meeting provided the scientific underpinning to the UNFCCC Executive Secretary’s call, expressed during the opening plenary, for governments to present strategies for achieving a 45% reduction in emissions by 2030 and reaching net-zero emissions by 2050. Moreover, considering the ongoing uncertainty about the ability of SIDS and least developed countries to participate in-person at the COP, given the continued pandemic, this virtual approval session also gives food for thought on alternative meeting arrangements.