Paul N. Edwards, the William J. Perry Fellow in International Security and Senior Research Scholar at CISAC, served as a lead author. Appointed to the IPCC in 2018, Edwards directs Stanford’s Program on Science, Technology and Society and co-directs Stanford’s Existential Risk Initiative. In his 2010 book, A Vast Machine: Computer Models, Climate Data, and the Politics of Global Warming, Edwards explained how scientists learned to measure earth’s atmosphere, understand its past, and predict its future. Here, Ewdards highlights important insights from the IPCC report and explains why this report matters for both present and future policy on climate change. The full report is available to read here.

Can you explain why this report matters?  

The IPCC reviews the state of climate knowledge every 6-7 years. Its reports evaluate virtually everything learned since the previous assessment. IPCC reports track the progression of human-caused climate change, project its possible future course, evaluate the risks to human and natural systems, and explore the likely consequences of the available policy options. The IPCC’s Fifth Assessment, completed in 2014, provided the main scientific input into the landmark Paris Agreement signed in 2015.

What’s coming out on Monday is the sixth report of Working Group I, which covers the physical science of climate change. It reflects major advances in understanding and greater certainty about the likely range of global heating over the 21^st century and beyond. Where previous reports focused on global to continental scales, this one will present more detailed projections for much smaller regions. It also covers short-lived climate forcers in depth – things like soot from coal smoke that don’t stay in the atmosphere very long, but have substantial effects on climate. 

Over the next year we’ll release the reports of the two other Working Groups. Working Group II covers vulnerability to climate change, how it affects us, and strategies for adapting to a warmer world. Working Group III covers mitigation: all the ways we can slow the progress of global heating, such as reducing greenhouse gas emissions and cleaning up air pollution.

Who produced this report?  

The Working Group I assessment was written by 234 scientists from around the world, with hundreds of others consulted for smaller contributions. As an intergovernmental organization under the United Nations, the IPCC makes a concerted effort to be as inclusive as possible. For example, 41 percent of WGI authors were from developing countries and 28 percent were women, while 31 percent had not participated in previous IPCC assessments.

IPCC assessments are the most heavily peer-reviewed documents in the history of science. First, they are based mainly on previously peer-reviewed, published science. (Working Group I cites over 14,000 scientific articles, most of them published since the last report in 2013.) Next, the assessment drafts are also reviewed several times: first internally, by the authors, then by experts and expert organizations, and finally by representatives of the IPCC’s member governments. We received over 23,000 comments on the first draft, and over 51,000 comments on the second – and we considered and responded to all of them!

Who needs to pay attention to it? 

Everyone! IPCC reports are aimed specifically at political leaders, policymakers, and their support staff who write detailed policy plans. But really, anyone who cares about the future of the planet should know about the main results of this assessment.

What is the intended impact of this report? 

IPCC reports are “policy neutral.” We provide knowledge about what’s already happened to the climate, what’s happening now, and what’s likely to happen under various policy scenarios, but we don’t recommend specific policies.

Those are choices best left to firms, cities, states, national governments, and international negotiations – but we believe those choices should be based on the most up-to-date, reliable knowledge. For example, the more detailed, regionally-focused information provided by this WGI report should help California policymakers better understand what’s coming.

Are we doomed? 

No, but we’re not safe either. By now most people understand that climate change is having dramatic effects, like the Southwest megadrought that began a few years ago and our increasingly awful fire seasons here in California. It’s bad, but we can stop it from getting worse, and every forward step will matter.

I believe we must do whatever we can to preserve a livable world for our children and their children’s children. The more effort and ideas we put into reducing our impact now, the more likely we are to avoid the worst future outcomes we can foresee.