IPCC

Data journey

Assessment reports

IPCC assessment reports are a collaborative effort involving thousands of researchers and governments from around the world.

The report is a systematic review of publications relevant to the scientific, technical and socio-economic aspects of climate change. The aim is to provide a comprehensive view of current knowledge.

Each assessment report covers three main areas of climate change research, each with its own working group:

These reports are further broken down into chapters covering specific themes within each of the three working groups. An additional synthesis report is also produced, which brings together the findings of the three working groups.

Climate scenarios

Each assessment report is underpinned by a set of climate scenarios. Over time new scenarios are produced to reflect developments in research and data, and increased sophistication in modelling. This is how the IPCC describes a scenario:

In climate change research, scenarios describe plausible trajectories of different aspects of the future that are constructed to investigate the potential consequences of anthropogenic climate change. Scenarios represent many of the major driving forces – including processes, impacts (physical, ecological, and socioeconomic), and potential responses that are important for informing climate change policy.

The goal of working with scenarios is not to predict the future but to better understand uncertainties and alternative futures, in order to consider how robust different decisions or options may be under a wide range of possible futures. – IPCC website

These scenarios cover factors such as carbon emissions, climate conditions, environmental conditions and socioeconomic vulnerability and ability to adapt to changes.

From AR4 to AR5 the process for generating the underlying scenarios fundamentally changed. The scenarios for AR5 were commissioned by the IPCC from the climate research community in 2006 before AR4 was even completed.

These scenarios are then used as the basis for the development of climate models that are produced by many different research groups. The Met Office Hadley Centre contributes the HadCM3, HadGEM2-CC, HadGEM2-ES and HadGEM2-A climate models to the process. Model data is made available to researchers around the world through four central repositories, including the British Atmospheric Data Centre in the UK.

The outputs from these models are then used as the basis for analysis which is published in the research literature on the physical science basis for climate change. This research is then reviewed in the working group one report for AR5.

Selecting the authors

Each of the three IPCC working groups has a team of authors who are experts in the field. These authors volunteer their time to work on the assessment report.

Authors are nominated to the IPCC by governments and observer organisations. Nominees’ detailed CVs are reviewed and authors are selected based on a variety of criteria including area of expertise, geographic location (developed and developing nations), gender and level of experience (experienced and newer scientists). Authors can come from research and academic organisations, industry and not-for-profit organisations.

Once selected, an author is assigned to a chapter that reflects their area of expertise. They may also be designated a lead or coordinating author. Those who have been nominated but not selected as an author, might become expert reviewers of the reports. In total 831 experts contributed to AR5. This process results in a formal structure for assembling the final reports.

Reviewing the literature

The IPCC does not conduct its own original research, rather it undertakes a systematic review of existing scientific research literature. The cut off date for AR5 was research published before 2012.

The IPCC does not conduct its own research, run models or make measurements of climate or weather phenomena. Its role is to assess the scientific, technical and socio-economic literature relevant to understanding climate change, its impacts and future risks, and options for adaptation and mitigation. Author teams critically assess all such information from any source that is to be included in the report. IPCC factsheet: What literature does the IPCC assess?

The systematic review covers research and other publications from around the world. Included in the review are publications authored by climate scientists at the Met Office and the Climatic Research Unit about their work on gridded datasets, climate models and other analyses published during the time period under consideration.

Examples include reports from governments, industry and research institutions, international and other organisations, and conference proceedings. Information about certain experiences and practices in mitigation and adaptation activities in particular may be found in sources other than traditional scientific and technical journals. IPCC factsheet: What literature does the IPCC assess?

Publications are submitted for review, and all publications that are reviewed are referenced, ensuring a high level of transparency for readers of the draft and final reports. The reviewers look not only at the publications, but also any sources related to them.

Reviewing the literature is a collaborative process. Chapter teams review the literature, and comments are collated for consideration by designated Review Editors before a draft report is compiled.

Drafting the report

The first draft reports are reviewed by a wide range of expert reviewers and governments who submit their comments to the working groups. Anybody can register to be a reviewer. The process relies on reviewers declaring their expertise when they engage with the process.

A second draft is then prepared, along with a summary for policymakers (SPM) which includes a series of headline statements. The SPM is a shorter document presenting key findings.

Following another round of expert reviews, final drafts are then prepared including a revised SPM report. Before publication, the SPM then undergoes a round of expert and government reviewing in order to reach a level of agreement about the findings of the review.

During the writing of the three working group reports for AR5, 136,706 comments were received from experts and governments and reviewed by the working groups. All of these comments are documented and published for transparency and reference purposes.

Final approval

Before the IPCC reports are published, they must go through a final process of approval by the 195 member governments of the IPCC.

As the culmination of a report’s development, IPCC member governments endorse the report. The endorsement process is based on a dialogue between those who will use the report – the governments – and those who write it – the scientists. Endorsement by governments acknowledges that the report is a definitive assessment that has been developed following the IPCC’s defined procedures, underpinning the report’s authority. – IPCC factsheet: How Does the IPCC Approve Reports?

The culmination of this process in AR5 WG1 led scientists and governments from around the world to conclude that:

Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.

Human influence on the climate system is clear. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions. – AR5 WG1 headline statements

Temperature data generated by Weston Park Museum weather station contributed significantly to the scientific understanding underlying these conclusions.

Key questions for climate scientists now are how climate change impacts particular locales and regions of the world differently, and to what extent regional weather conditions are attributable to climate change.

Our temperature datum – generated in June 2014 by the newly installed Met Office equipment at Weston Park – will make a contribution to climate scientists’ efforts to answer such questions. Similarly, amateur observer and Professor of Climate Change, Edward Hanna hopes that the observation data he is generating will contribute to understanding more about the local impacts of climate change.