Its findings influence governments, business leaders and even young protesters on one of the biggest issues facing the planet: the climate crisis.
But many people may never have heard of the Intergovernmental Panel on Climate Change (IPCC).
The IPCC is a UN body that evaluates climate science. It brings together leading scientists to study climate change and how it is reshaping the world. It also explores solutions to cut emissions and adapt to a hotter planet.
Founded in 1988 by the World Meteorological Organization and the United Nations Environment Program, the IPCC produces major assessments every few years. The reports are dense documents thousands of pages long — but are accompanied by summaries for policymakers that are intended for a broader readership.
Gold-standard for climate science
To write these reports, the IPCC selects hundreds of scientists from across the world to evaluate peer-reviewed scientific literature and, less often, government and industry reports. In that sense, none of the findings in the reports are new. The scientists consider thousands of studies when writing their assessments.
The most recent publication is the IPCC's sixth assessment report. It published the first installment on the physical science of climate change in August 2021. The second section, on the effects and adaptation, was released in February. The third section on slowing climate change and cutting emissions is out in April. It will be completed by a synthesis report published in September.
The sixth assessment comes after a series of special reports published in 2018 and 2019 that covered projections for life on a planet that will have warmed 1.5 degrees Celsius (2.7 degrees Fahrenheit), and the effects of climate change on land, oceans and icy places. The special report on 1.5 C of warming is credited with forcing journalists to pay more attention to climate change.
Projections, not predictions
IPCC climate scientists stress that they do not tell governments what to do, but rather assess different pathways they could take. In UN jargon, they say they are "policy-relevant but not policy-prescriptive."
They also say their conclusions for the future are projections — based on different warming scenarios — rather than predictions.
The summaries for policymakers they publish with each report are prepared by experts and reviewed line-by-line in marathon plenary sessions by UN member states who must then unanimously approve them. These documents guide decision-makers.
But while the science in the reports themselves is left entirely to the experts, the inclusion of governments in the review process has raised criticisms this lets politicians water down the conclusions. For instance, the sixth assessment report on the physical science of climate change did not mention the words "fossil fuels" in its 40-page summary for policymakers because Saudi Arabia successfully lobbied to remove it.
IPCC authors stress that they can — and do — push back on comments that are not justified by the science. Among scientists, the reports are viewed as the most comprehensive and reliable assessments of climate change.
In 2007, the IPCC was awarded the Nobel Peace Prize.
This is an updated version of a previous article.