Making Sense of the 2021 Climate Change Report
Updated: Nov 16
The media has been abuzz with talk of the latest climate change report that was released on August 9th. I’ve been working my way through the report and associated documents, trying to understand its findings for myself. It’s not easy! The report is nearly 4000 pages of technically complex information. I can’t do it justice in a blog post, but I’ll try to provide some context and perspective. Feel free to comment or send me specific questions about the report. I’d be glad to research them for you and see if the report addresses it.
The official title of the report is Climate Change 2021: The Physical Science Basis. It’s part one of a three-part report. The entire report is a project of the Intergovernmental Panel on Climate Change (IPCC), which was formed in 1988 by the World Meteorological Organization and the United Nations Environment Progamme. The IPCC’s objective is to provide governments around the world with scientific information to use in developing climate policy.
The IPCC does not make policy, nor does it conduct research or climate modeling. Instead, it convenes working groups to compile and assess vetted, peer-reviewed, and published research that was conducted by scientists around the world. Working groups look for areas of agreement in the data and evaluate the level of confidence they have in the information based on the extent and quality of the data and research methodology. The IPCC has done this periodically since 1988. The recently issued report is part of the IPCC’s sixth assessment of climate change.
Climate Change 2021: The Physical Science Basis updates our understanding of the climate system as it is today. The report discusses the physical science of the climate system, changes in it, and human influence on the system. What the physical data means to ecosystems and human societies, potential adaptations and vulnerabilities, and the technical viability of mitigation measures will be addressed in the next two parts of the report. They are Climate Change 2022: Impacts, Adaptation, and Vulnerability (February 2022) and Climate Change 2022: Mitigation of Climate Change (March 2022).
The United States is actively participating in the working group for each of these reports. The authors listed for Climate Change 2021: The Physical Science Basis include at least five scientists from the National Oceanic and Atmospheric Administration (NOAA), scientists from at least four other federally funded research centers, and researchers from university systems in over ten U.S. states. The working group looked at over 14,000 published reports of climate research. Their assessment presents findings with clearly stated levels of confidence and likelihood.
“In 2019, atmospheric CO2 concentrations were higher than at any time in at least 2 million years (high confidence), and concentrations of CH4 and N2O were higher than at any time in at least 800,000 years (very high confidence).” – In this example, you see how the period of record and the scientific methods used result in a difference between “high” and “very high” confidence.
“It is virtually certain that the global upper ocean (0-700 m) has warmed since the 1970s and extremely likely that human influence is the main driver.” – This example shows the nuance between “virtually certain” from directly observed and measured temperature data to “extremely likely” based on the scientific agreement of the research.
The report’s key findings are summarized in a fact sheet that unfortunately calls the findings “headlines.” I almost ignored the fact sheet, thinking it was merely attention-getting statements for the media to use. When I read the full document, I discovered these “headlines” are a roll-up of the most important findings. It’s what some might call BLUF – Bottom Line Up Front.
Here are some of the takeaways from what I’ve read of the report so far. Statements in italics are quotes from the report and its associated documents.
“It is unequivocal that human influence has warmed the atmosphere, ocean, and land.”
The current observed average global surface temperature is warmer than “the estimated temperature (very likely range) during the warmest multi-century period in at least 100,000 years, which occurred around 6500 years ago during the current interglacial period (Holocene).”
Direct observations indicate climate change is already affecting weather extremes.
Emissions from human activities have increased concentrations of greenhouse gases in the atmosphere, which is part of the climate system. As with any system, it takes time for the effects of a change in one part of the system to be felt throughout the system and reach a new equilibrium. With climate, the process takes decades and increases the average global surface temperature. Based on the current concentration of greenhouse gases in the atmosphere, equilibrium will be reached within “a likely range of 2.5°C to 4°C (high confidence).” The working group’s “best estimate is 3°C,” for the long-term increase, or 5.4°F, if greenhouse gas concentrations remain the same as they are now.
Because of the time lag in climate system response, warming is already underway and unavoidable in the short-term, even if we take action to keep warming from reaching 3°C. Under all emissions scenarios considered, it’s “very likely” average global surface temperature will rise from 1.2°C to 1.9°C by year 2040.
Data shows with “high confidence” that “there is a near-linear relationship between cumulative anthropogenic CO2 emissions and the global warming they cause.” This is good news! It means we can stop the temperature increase and even reverse it. The report indicates achieving global net zero emissions around or after year 2050, followed by action to remove CO2 from the atmosphere, is “very likely” to keep the long-term, average global surface temperature to within 1.0°C to 1.8°C.
It’s within our ability to limit the rise of average global temperature; however, “if global net negative CO2 emissions were to be achieved and be sustained, the global CO2-induced surface temperature increase would be gradually reversed but other climate changes would continue in their current direction for decades or millennia (high confidence).” One example is sea level rise.
The long-term effects of climate change are regional in nature. Confidence in regional data is not as high as global climate data and will require more data and research. A Regional Fact Sheet for North and Central America summarizes the current understanding for our region.
The IPCC has made many summary graphics with more technical details available for viewing in this PDF file.
For me, working through the technical data is not nearly as difficult as working through what it means for me and the remainder of my time on Earth. Since I’m part of the climate system, and my life is sustained by elements of it, a changing climate means I will have to change my lifestyle in response. The only question is whether I choose to be proactive and part of the long-term solution or wait and react when the damage is done.
The choice of waiting is one of privilege. The impacts of climate change will be felt by all of us in the short-term, but some are more vulnerable to the impacts than others. People who work outside or are living in low-lying coastal areas are already experiencing observed impacts of climate change and don’t have the choice of waiting to respond.
The unequal effects of climate change raise many questions, as I think about service to others, ministry, and general love of neighbor.
Who is vulnerable to heat in my community?
Who is vulnerable to flooding, wildfires, and other extreme events?
What would drought mean to the livelihoods of people in my community?
Who would be vulnerable to food insecurity if drought increased food prices?
Who is vulnerable to the increased health risks that come with climate change?
Whose water supply is at risk?
In general, am I considering the known impacts of climate change on the people who I serve and accounting for it in my projects, programs, and ministry? Am I even accounting for it in my own life decisions? Do I mention climate change as a known factor to consider when discussing work or personal decisions with others?
I find the intergenerational nature of climate change challenging. How and where do I find sustenance for a life-long response to climate change, even though I will not live to see the results? How can I draw upon my faith and its traditions of sacrifice for others?
Finally, I see a connection between good science and good theology. Both require me to acknowledge the limits of my understanding and proceed anyways. I would become paralyzed with inaction if I waited to have all the information I wanted and knew the outcome before I acted on things in life. Instead, I’m called to make a reverent best guess, and then step out in faith. I may not get it right, but grace abounds, and I can try again. This is true in any endeavor. It’s true in ministry, and it’s true in response to climate change.