The Science on Climate Change

There seems to be some confusion about what scientists know about climate change and its impacts. If you're interested to know more, read on.

You may notice all of this information is from the Intergovernmental Panel on Climate Change (IPCC), which is described in detail further down in this article. And I think that while the IPCC is a fantastic, transparent, vetted source of all hard science related to climate change. It's also a huge group with lots of working groups, organizations, governments, task forces, staff, committees, bureaus, authors, editors, and reviewers. Not to mention the thousands of peer-reviewed articles in scientific journals and technical publications which provide the essential foundation for IPCC assessments.

It's so much information that it's complicated to navigate.

Complication opens the door for confusion.

And through that door continues to march a steady and vocal [though small] stream of climate deniers and skeptics.

The next Assessment Report (AR6 Climate Change 2021) is anticipated for April 2021. The most recent previous summary report, except the special reports (SR) noted below, is AR5 from the fifth IPCC assessment cycle. This article is an attempt to summarize the currently available information as provided by the IPCC.

Special Report, Sept. 2019: The Ocean and Cryosphere in a Changing Climate

All people on Earth depend directly or indirectly on the ocean and cryosphere. The global ocean covers 71% of the Earth surface and contains about 97% of the Earth’s water. The cryosphere refers to frozen components of the Earth system1. Around 10% of Earth’s land area is covered by glaciers or ice sheets. The ocean and cryosphere support unique habitats, and are interconnected with other components of the climate system through global exchange of water, energy and carbon. The projected responses of the ocean and cryosphere to past and current human-induced greenhouse gas emissions and ongoing global warming include climate feedbacks, changes over decades to millennia that cannot be avoided, thresholds of abrupt change, and irreversibility.

Special Report, Aug. 2019: Climate Change and Land

This Special Report on Climate Change and Land 1 responds to the Panel decision in 2016 to prepare three Special Reports during the Sixth Assessment cycle, taking account of proposals from governments and observer organisations. This report addresses greenhouse gas (GHG) fluxes in land-based ecosystems, land use and sustainable land management in relation to climate change adaptation and mitigation, desertification, land degradation and food security.

Special Report, Oct. 2018: Global Warming of 1.5°C

Human activities are estimated to have caused approximately 1.0°C of global warming above pre-industrial levels, with a likely range of 0.8°C to 1.2°C. Global warming is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate. (high confidence) Warming from anthropogenic emissions from the pre-industrial period to the present will persist for centuries to millennia and will continue to cause further long-term changes in the climate system, such as sea level rise, with associated impacts (high confidence), but these emissions alone are unlikely to cause global warming of 1.5°C (medium confidence). Climate-related risks for natural and human systems are higher for global warming of 1.5°C than at present, but lower than at 2°C (high confidence). These risks depend on the magnitude and rate of warming, geographic location, levels of development and vulnerability, and on the choices and implementation of adaptation and mitigation options (high confidence).

Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation

Extreme weather and climate events, interacting with exposed and vulnerable human and natural systems, can lead to disasters. This Special Report explores the challenge of understanding and managing the risks of climate extremes to advance climate change adaptation. Weather- and climate-related disasters have social as well as physical dimensions. As a result, changes in the frequency and severity of the physical events affect disaster risk, but so do the spatially diverse and temporally dynamic patterns of exposure and vulnerability. Some types of extreme weather and climate events have increased in frequency or magnitude, but populations and assets at risk have also increased, with consequences for disaster risk. Opportunities for managing risks of weather- and climate-related disasters exist or can be developed at any scale, local to international. Some strategies for effectively managing risks and adapting to climate change involve adjustments to current activities. Others require transformation or fundamental change. 

Working Group I: The Physical Science Basis

WG I assesses the physical science of climate change. The scientific topics assessed by WGI include: greenhouse gases and aerosols in the atmosphere; temperature changes in the air, land and ocean; the hydrological cycle and changing precipitation (rain and snow) patterns; extreme weather; glaciers and ice sheets; oceans and sea level; biogeochemistry and the carbon cycle; and climate sensitivity. 

AR5 Climate Change 2013: The Physical Science Basis

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. 

Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. In the Northern Hemisphere, 1983–2012 was likely the warmest 30-year period of the last 1400 years (medium confidence). Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energy accumulated between 1971 and 2010 (high confidence). It is virtually certain that the upper ocean (0–700 m) warmed from 1971 to 2010, and it likely warmed between the 1870s and 1971. Over the last two decades, the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent (high confidence). The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia (high confidence). Over the period 1901 to 2010, global mean sea level rose by 0.19 [0.17 to 0.21] m. The atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. Carbon dioxide concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification.  

Summary for Policymakers

Working Group II: Impacts, Adaption and Vulnerability

WG II assesses the impacts of climate change, from a world-wide to a regional view of ecosystems and biodiversity, and of humans and their diverse societies, cultures and settlements. It considers their vulnerabilities and the capacities and limits of these natural and human systems to adapt to climate change and thereby reduce climate-associated risks together with options for creating a sustainable future for all through an equitable and integrated approach to mitigation and adaptation efforts at all scales.

AR5 Climate Change 2014: Impacts, Adaptation, and Vulnerability

Human interference with the climate system is occurring, and climate change poses risks for human and natural systems. The assessment of impacts, adaptation, and vulnerability in the Working Group II contribution to the IPCC’s Fifth Assessment Report (WGII AR5) evaluates how patterns of risks and potential benefits are shifting due to climate change. It considers how impacts and risks related to climate change can be reduced and managed through adaptation and mitigation. The report assesses needs, options, opportunities, constraints, resilience, limits, and other aspects associated with adaptation. Climate change involves complex interactions and changing likelihoods of diverse impacts. A focus on risk, which is new in this report, supports decision making in the context of climate change and complements other elements of the report. People and societies may perceive or rank risks and potential benefits differently, given diverse values and goals.

Summary for Policymakers

Working Group III: Mitigation of Climate Change

WG III focuses on climate change mitigation, assessing methods for reducing greenhouse gas emissions, and removing greenhouse gases from the atmosphere.

Greenhouse gases can come from a range of sources and climate mitigation can be applied across all sectors and activities. These include energy, transport, buildings, industry, waste management, agriculture, forestry, and other forms of land management.

Working Group III supports the IPCC’s solution-oriented approach but does not advocate any specific mitigation options. It takes both a near-term perspective relevant to decision-makers in government and the private sector and a long-term perspective that helps identify how high-level climate policy goals might be met.

AR5 Climate Change 2014: Mitigation of Climate Change

Mitigation is a human intervention to reduce the sources or enhance the sinks of greenhouse gases. Mitigation, together with adaptation to climate change, contributes to the objective expressed in Article 2 of the United Nations Framework Convention on Climate Change (UNFCCC):

The ultimate objective of this Convention and any related legal instruments that the Conference of the Parties may adopt is to achieve, in accordance with the relevant provisions of the Convention, stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner.

Climate policies can be informed by the findings of science, and systematic methods from other disciplines.

Summary for Policymakers

TFI: The Task Force on National Greenhouse Gas Inventories

The Task Force on National Greenhouse Gas Inventories (TFI) develops and refines an internationally-agreed methodology and software for the calculation and reporting of national GHG emissions and removals and encourages the use of this methodology by countries participating in the IPCC and by signatories of the United Nations Framework Convention on Climate Change (UNFCCC).

• Methodology Report on Short-lived Climate Forcers
• 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories
• 2006 IPCC Guidelines for National Greenhouse Gas Inventories

The Intergovernmental Panel on Climate Change brings together experts from all around the world.

The science for all this comes from the Intergovernmental Panel on Climate Change.

If you aren't familiar with the Intergovernmental Panel on Climate Change (IPCC), it is the United Nations body for assessing the science related to climate change. It was created in 1988 by the World Meterological Organization (WMO) and the United National Environment Programme (UNEP) to provide governments around the world with all levels of scientific information they can use to develop climate policies, the implications of climate change, and potential future risks, as well as to put forward adaptation and mitigation options.

The IPCC is an organization of governments that are members of the United Nations or WMO. The IPCC currently has 195 member countries and each country has a national focal point contact. Representatives of the IPCC member governments meet in Plenary Sessions attended by hundreds of officials and experts from relevant agencies, research institutions, and Observer Organizations.

The panel works by consensus to decide on the organization's budget and work programme; the scope and outline of its reports; issues related to principles and procedures; and the structure and mandates of the IPCC Working Groups and Task Forces. The Panel also approves and adopts IPCC reports and elects the IPCC Chair, other members of the IPCC Bureau and the Task Force Bureau.

Observer Organizations

Any non-profit body or agency qualified in matters covered by the IPCC may be admitted as an Observation Organization. There are currently 150+ observer organizations.

The IPCC Bureau

The panel elects a bureau to provide guidance on scientific and technical aspects of its work, advise on related management and strategic issues, and take decisions on specific issues within its mandate. The bureau includes the IPCC Chair, Vice-Chairs, Co-Chairs, and Vice-Chairs of the three Working Groups as well as the Co-Chairs of the Task Force on National Greenhouse Gas Inventories. It currently has 34 members. None of them is paid by the IPCC. Members of the Bureau are elected by the Panel for the duration of an assessment cycle and must reflect a balanced geographic representation, with due consideration for scientific and technical requirements.

The Task Force Bureau (TFB)

The Task Force on National Greenhouse Gas Inventories (TFI) has its own Task Force Bureau (TFB) composed of 12 members and the two Co-Chairs of the TFI. The TFB overseas the National Greenhouse Gas Inventories Programme. The term of the TFB is normally the same as the term of the IPCC Bureau, and its members are elected at the same Session at which the IPCC Bureau is elected, unless decided otherwise by the Panel. Elections for the current IPCC Bureau and Task force Bureau were held during the 42nd Session of the IPCC in Dubrovnik, Croatia in October 2015. Results of the elections are available here.

The Executive Committee

The IPCC Chair, IPCC Vice-Chairs, and the Co-Chairs of the three Working Groups and the Task Force on National Greenhouse Gas Inventories form the Executive Committee (ExCom). The ExCom’s role is to strengthen and facilitate the timely and effective implementation of the IPCC work programme in accordance with the IPCC’s Principles and Procedures, the decisions of the Panel, and the advice of the Bureau. It includes as advisory members the head of the IPCC Secretariat and the heads of the Technical Support Units of the Working Groups and TFI. It meets regularly and its meetings are chaired by the IPCC Chair.

IPCC Authors and Review Editors

Hundreds of leading experts in the different areas covered by the IPCC reports volunteer their time and expertise as Coordinating Lead Authors (CLAs), Lead Authors (LAs) Contributing Authors (CAs) and Review Editors (REs) to prepare IPCC Reports.

Authors are selected on the basis of their expertise following a call to governments, Observer Organizations and the IPCC Bureau for nominations and the submission of detailed resumes. After the nomination deadline, the Bureau of the relevant IPCC Working Group or Task Force selects the experts for these roles, taking into account the range of scientific, technical and socio-economic views and backgrounds, as well as geographical and gender balance. They also ensure that the teams include a mixture of experts with and without previous IPCC experience. This ensures that reports are not biased towards the perspective of any one region and that questions of importance to particular groups are not overlooked. Author teams may also involve experts from industry and from non-governmental organizations who can bring a valuable perspective to the assessment.

For each IPCC report, authors produce two report drafts that undergo an external expert review. All the comments made during the review periods are collected and must be taken into account by the author teams when producing the subsequent draft. To support this process, each chapter team also has at least two Review Editors. They help identify expert reviewers, ensure that all substantive comments are afforded appropriate consideration, and advise Lead Authors on how to handle potential issues. These roles require considerable experience. Read here for how IPCC selects its authors, and here for a database of IPCC authors (there are over 850 authors).

Expert Reviewers

The IPCC is committed to preparing reports assessing the current state of knowledge of the science related to climate change that aim for the highest standards of scientific excellence, balance and clarity. To achieve this, each report undergoes two review periods:

1. an Expert Review of the First Order Draft
2. and a Government and Expert Review of the Second Order Draft.

This review process includes wide participation, with hundreds of reviewers commenting on the accuracy and completeness of the scientific assessment contained in the drafts.

Beyond these official IPCC roles, thousands of scientists and experts worldwide contribute to IPCC assessments by adding to the body of scientific literature. Thousands of peer-reviewed articles in scientific journals and technical publications provide the essential foundation for IPCC assessments.

The Secretariat

The Secretariat coordinates and assists the work of the Intergovernmental Panel on Climate Change and is located in Geneva, Switzerland, in the building of the World Meteorological Organization, and includes 13 staff.

It organizes IPCC Plenary, Bureau and Executive Committee meetings and provides administrative support for these, including the preparation of documents and reports.

It supports, as required, the Working Groups, the Task Force on National Greenhouse Gas Inventories, and any other task force, task group or committee established by the IPCC in the organization of their activities and meetings.

Technical Support Units

Each Working Group and the Task Force on National Greenhouse Gas Inventories is supported by a Technical Support Unit (TSU). The TSUs provide scientific, technical and organizational support and support the Co-Chairs and Bureaux in the preparation and production of all relevant IPCC products. A TSU may also be formed to support the preparation of a Synthesis Report or any other Task Force constituted by the Panel.

The TSUs for the Sixth Assessment Report are hosted by France (Working Group I TSU, 14 staff); Germany and South Africa (Working Group II TSU, 17 staff not including their morale officer, who is a dog), the United Kingdom and India (Working Group III TSU, 13 staff) and Japan (Task Force on the National Greenhouse Gas Inventories TSU, 6 staff). The Working Group I TSU has a satellite office in China, Working Group II in South Africa and Working Group III in India.

What does All This Mean?

Thousands of people from all over the world contribute to the work of the IPCC. For the assessment reports, IPCC scientists volunteer their time to assess the thousands of scientific papers published each year to provide a comprehensive summary of what is known about the drivers of climate change, its impacts and future risks, and how adaptation and mitigation can reduce those risks. You can read through 22 pages of authors and expert reviewers and count the names here.

The IPCC determines the state of knowledge on climate change.

Through its assessments, the IPCC determines the state of knowledge on climate change.

• It identifies where there is agreement in the scientific community on topics related to climate change, and where further research is needed.
• The reports are drafted and reviewed in several stages, to maintain objectivity and transparency.  
• The IPCC does not conduct its own research.
• IPCC reports are neutral, policy-relevant but not policy-prescriptive.  
• The assessment reports are a key input into the international negotiations to tackle climate change.

THIS is The Science on Climate Change. And it is not really up for debate, or open to opinion.

There really are scientific debates out there that can be full of drama and inspire researchers to new heights of originality. This is the essence of the scientific process (collect data, analyse, deduce, repeat).

Confusing the process with vastly exaggerated or fundamentally false claims of disagreement (often by the media and politicians) is giving a false impression of scientific research and the opinions of the scientific community.

There is no need to dramatize every slight disagreement as equal to a body of evidence. We should be better than this, but we're not... Humans love drama.

Just please try to remember that not every disagreement in science is a scientific debate, and a tiny but vocal minority should not be given parity without the same weight of data and evidence.