By Ray Johnson

Welcome to both first-time and returning readers. Episode One was a primer on the Intergovernmental Panel on Climate Change (the IPCC) and the framework for governments to act on IPCC advice, with a final sentence “Time is running out.” A lot has happened since. The unprecedented weather events in south-east Queensland and northern NSW are but one expression of climate change.

Today we look at the three IPCC Assessment Working Groups. It’s timely, as on 1 March the IPCC agreed (media release) on the outlines for each Working Group contribution (21 page pdf version) to the Seventh Assessment Report (AR7) scheduled for delivery late 2029. The pdf contains all Working Group outlines.

Working Group I (WGI), The Physical Science Basis, assesses the science basis of the non-living systems associated with climate change. Topics include: greenhouse gases and aerosols; temperature changes (air, land and ocean); the hydrological (water) cycle and changing rain and snow patterns; extreme weather; glaciers and ice sheets; oceans and sea level; biogeochemistry and the carbon cycle; and climate sensitivity. (p1-13 of pdf)

Working Group II (WGII), Impacts, Adaptation and Vulnerability, assesses “the vulnerability of socio- economic and natural systems to climate change, negative and positive consequences of climate change and options for adapting to it.” The first dot point of the first chapter of the draft WGII outline is “Facing accelerating climate change and adapting to compounding threats in a poly-crisis world.” This gives a strong hint of the path the science is predicting. The IPCC also approved an outline for an update to the 1994 IPCC Technical Guidelines for Assessing Climate Change Impacts and Adaptations.

(p14-15 of pdf)

Working Group III (WGIII) focuses on climate change mitigation, assessing methods for reducing greenhouse gas emissions, and removing greenhouse gases from the atmosphere. This groups Sixth Assessment Report stated up front: “Globally, gross domestic product (GDP) per capita and population growth remained the strongest drivers of CO2 emissions from fossil fuel combustion in the last decade (robust evidence, high agreement). Trends since 1990 continued in the years 2010 to 2019 with GDP per capita and population growth increasing emissions by 2.3% and 1.2% yr –1, respectively.“ Yes it’s us. This outline is wide-ranging, complex and detailed. (p16-21 of pdf)

WGI (Physical Science) also provided a Background Information paper for the IPCC approval meeting agenda item. Descriptions of various consultations highlight both agreement and debates within a wide range of specialist areas. The language is accessible, high-level not overly technical, and clear headings allow sections that may not be of interest to be skimmed or skipped e.g. procedural sections.

At 55 pages it’s a bit of a read but I strongly recommend at least a skim of Section 8. Annotated Outline of the AR7 WGI Chapters (p15-30) to anyone studying climate change or involved in planning or policy development. There’s an insight for everyone. Best read with the Outline pdf open as well.

Some might find it fascinating … I did. My takeouts were:

• The extent and depth of consultation – remember this is just for the outlines

• The rationales for the decisions including significant changes from the WGI AR6 report

• The sense that much of the earlier science has either been accepted or rejected (more concise)

• The stronger focus on regional climate change

• The exploration of “Abrupt changes, tipping points and high impact events in the Earth system”

• The emphasis on better coordination – “Favor interdisciplinary interactions with other WGs”

• The transparency and accountability of the process.