Editing IPCC:AR6/WGI/Chapter-1 (section)

== 1.7 Final Remarks ==

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The assessment in this Report is based on a rapidly growing body of new evidence from the peer-reviewed literature. Recently, scientific climate change research has doubled in output every 5–6 years; the majority of publications deal with issues related to the physical climate system ( [[#Burkett--2014|Burkett et al., 2014]] ; [[#Haunschild--2016|Haunschild et al., 2016]] ). The sheer volume of published, peer-reviewed literature on climate change presents a challenge to comprehensive, robust and transparent assessment.

The enhanced focus on regional climate in AR6 WGI further expands the volume of literature relative to AR5, including non-English language publications sometimes presented as reports (‘grey’ literature), particularly on topics such as regional observing networks and climate services. These factors enhance the challenge of discovering, accessing and assessing the relevant literature. The international, multilingual author teams of IPCC AR6, combined with the open expert-review process, help to minimize these concerns, but they remain a challenge.

Despite the key role of CMIP6 in this Report ( [[#1.5|Section 1.5]] ), the number of studies evaluating its results and modelling systems remains relatively limited. At the time of publication, additional model results are still becoming available. This reflects the need for close temporal alignment of the CMIP cycle with the IPCC assessment process, and the growing complexity of coordinated international modelling efforts.

Indigenous and local knowledge includes information about past and present climate states. However, assessing this knowledge, and integrating it with the scientific literature, remains a challenge to be met. This lack of assessment capability and integration leads to most WGI chapters still not including indigenous and local knowledge in their assessment findings.

Spatial and temporal gaps in both historical and current observing networks, and the limited extent of paleoclimatic archives, have always posed a challenge for IPCC assessments. A relative paucity of long-term observations is particularly evident in Antarctica and in the depths of the ocean. Knowledge of previous cryospheric and oceanic processes is therefore incomplete. Sparse instrumental temperature observations prior to the industrial revolution make it difficult to uniquely characterize a ‘pre-industrial’ baseline, although this Report extends the assessment of anthropogenic temperature change further back in time than previous assessment cycles ( [[IPCC:Wg1:Chapter:Chapter-7|Chapter 7]] and Cross-Chapter Box 1.2).

Common, integrating scenarios can never encompass all possible events that might induce radiative forcing in the future ( [[#1.4|Section 1.4]] ). These may include large volcanic eruptions (Cross-Chapter Box 4.1), the consequences of a major meteorite, smoke plumes following a conflict involving nuclear weapons, extensive geoengineering, or a major pandemic (Cross-Chapter Box 1.6). Scenario-related research also often focuses on the 21st century. Post-2100 climate changes are not covered as comprehensively, and their assessment is limited. Those long-term climate changes, potentially induced by forcing over the 21st century (as in the case of sea level rise), are nevertheless relevant for decision-making.

At the time of publication, the consequences of the COVID-19 pandemic on emissions, atmospheric abundances, radiative forcing and the climate (Cross-Chapter Box 6.1), and on observations ( [[#1.5.1|Section 1.5.1]] ), are not yet fully evident. Their assessment in this Report is thus limited.

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