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Header photo: Antarctic Sea ice reaches another record low (February 2023). NASA Earth Observatory, public domain.

So, do you love your children? Your grandchildren? Your neighbor? Contemplating sacrificial love this Lent? 

Hold that thought.

You may have missed it amid wall-to-wall coverage of a tawdry conman possibly having to face justice (alas), but the Intergovernmental Panel on Climate Change (IPCC) released its scheduled 6th Assessment Report (AR6) on March 20 ( I read the full report on Sunday (85 pages) and you should too. Without hyperbole, it is the most important thing to have happened in the past two weeks. 

The full AR6 report has 56 authors and 28 contributing authors and was reviewed by 14 editors with oversight from IPCC’s Scientific Steering committee (30 people). The team represents countries and governments from around the world and assesses the looming climate justice crisis through the lenses of physical, chemical, and biological sciences, yes – but also social sciences, political science, and economics. I am aware of no scientific enterprise, even medicine, where assertions are more carefully vetted, tested, and scrutinized.

Concern for justice, particularly for the world’s poor and vulnerable, bleeds from nearly every paragraph. 

The report is a careful assessment of the Crisis’s current status and trends, long-term climate and development futures, and humanity’s near-term responses in a changing climate. It is a synthesis of current and emergent science (peer-reviewed journal publications) that adopts an explicit parenthetical classification of scientific-consensus-based confidence on assertions it makes. To illustrate, I might glance at the weather report for Madison and write, “The sun will rise at 6:45 am CST on 3/29 (very high confidence) and daytime temperatures in the high 30°s F probably will prevent the remnant snow from melting completely (high confidence) however net snow accumulation will decline despite flurries predicted for the afternoon (moderate confidence).”

This is important. Scientists are trained to quantify their uncertainty about observation patterns and predictions using rigorous statistical theory and experimental design principles; these are not subjective opinions. The authors are trying to capture and translate this for the reader. 

With that in mind, here’s the summary of current status and trends: 

Human activities, principally through emissions of greenhouse gases, have unequivocally caused global warming, with global surface temperature reaching 1.1°C above 1850-1900 in 2011-2020. Global greenhouse gas emissions have continued to increase over 2010-2019, with unequal historical and ongoing contributions arising from unsustainable energy use, land use and land-use change, lifestyles and patterns of consumption and production across regions, between and within countries, and between individuals (high confidence). Human-caused climate change is already affecting many weather and climate extremes in every region across the globe. This has led to widespread adverse impacts on food and water security, human health and on economies and society and related losses and damages to nature and people (high confidence). Vulnerable communities who have historically contributed the least to current climate change are disproportionately affected (high confidence). (p.6)

Note that 1°C (Celsius) is about 2° Fahrenheit. Critically, climate warming is a function of cumulative emissions of greenhouse gas emissions (GHG) and global surface temperatures have risen faster since 1970 than during any 50-year period in the last 2000 years (high confidence, p.6). North America is the largest contributor to cumulative GHG emissions (23%, 1850-2019) and our recent (2019) per-person contribution is 19 tons per year, most (about 15 tons) coming from fossil fuels. Our nearest competitors in the dubious distinction are in Europe, Japan, New Zeeland and the Middle East (each about 13 tons total). East Asians contribute 11 tons while South Asians and Africans contribute 3-4 tons (p.9).   

Regarding long-term trends:

Future warming will be driven by future emissions and will affect all major climate system components, with every region experiencing multiple and co-occurring changes. Many climate-related risks are assessed to be higher than in previous assessments, and projected long-term impacts are up to multiple times higher than currently observed. Multiple climatic and non-climatic risks will interact, resulting in compounding and cascading risks across sectors and regions. Sea level rise, as well as other irreversible changes, will continue for thousands of years, at rates depending on future emissions. (high confidence) (p.33)

AR6 is notable because for the first time in an IPCC cycle, model predictions of global surface temperature, ocean warming, and sea level have become more certain because actual observations since AR5 (2014) confirm earlier predictions and inform and enhance model predictions for the future. 

Given policies in place at the end of 2020, model predictions are that global warming will increase to 3.2C° (range: 2.2 – 3.5) by 2100. What does that mean (remember, we’re at about 1.1C now)?

Climate-related risks to health, livelihoods, food security, water supply, human security, and economic growth are projected to increase with global warming of 1.5°C. In terrestrial ecosystems, 3–14% of the tens of thousands of species assessed will likely face a very high risk of extinction at a GWL of 1.5°C. Coral reefs are projected to decline by a further 70–90% at 1.5°C of global warming (high confidence). 

With about 2°C warming, climate-related changes in food availability and diet quality are estimated to increase nutrition-related diseases and the number of undernourished people, affecting tens (under low vulnerability and low warming) to hundreds of millions of people (under high vulnerability and high warming), particularly among low-income households in low- and middle-income countries in sub-Saharan Africa, South Asia and Central America (high confidence)

The need to address climate injustice is the most urgent thing facing humanity:

Deep, rapid and sustained mitigation and accelerated implementation of adaptation reduces the risks of climate change for humans and ecosystems. In modeled pathways that limit warming to 1.5°C (>50%) with no or limited overshoot and in those that limit warming to 2°C (>67%) and assume immediate action, global GHG emissions are projected to peak in the early 2020s followed by rapid and deep reductions. As adaptation options often have long implementation times, accelerated implementation of adaptation, particularly in this decade, is important to close adaptation gaps. (high confidence) (p.56)

Many changes in the climate system, including extreme events, will become larger in the near term with increasing global warming (high confidence). Multiple climatic and non-climatic risks will interact, resulting in increased compounding and cascading impacts becoming more difficult to manage (high confidence). Losses and damages will increase with increasing global warming (very high confidence), while strongly concentrated among the poorest vulnerable populations (high confidence). Continuing with current unsustainable development patterns would increase exposure and vulnerability of ecosystems and people to climate hazards (high confidence). (p. 62)

Achieving that 1.5°C increase (above) with minimal overshoot is the absolute best thing we can hope for but it requires radical transformation of economies, policies, and thinking. There are helpful and hopeful assessments – particularly on the cost-effectiveness of renewable energy sources (becoming cheaper than fossil fuel alternatives, p.20), countries making progress to net zero emissions, and increased adaptation financing but these positive trends are not yet meeting the magnitude or urgency of the need. 

That need is both maddeningly simple in principle and maddeningly complex in implementation. Humanity needs to stop using fossil fuels for the most part, stop investing in fossil fuel infra-structure (because it “locks-in” emissions and accelerating negative impacts, p. 43) and mobilize every technology, from reforestation to emerging carbon-capture chemistries, to remove GHGs from the atmosphere. The report explicitly describes needing to wrestle with known fossil fuel reserves becoming “stranded assets” (pp. 24, 59-60; i.e., “keep it in the ground”). 

The adaptation and long-term projection assessments are steeped in concern for the well-being of the world’s poor. If transition to a sustainable emissions future globally requires that near-term development and human flourishing for the world’s poor be fueled by fossil fuels, there are essentially two pools from which to draw: 1) the world’s known and unexploited fossil fuel reserves and 2) the waste, inefficiency, and fossil fuel gluttony of the developed countries – mostly in the global North. Drawing from pool 1 creates negative synergies that feedback to more damage and human suffering (the cumulative problem of GHGs and climate forcing). Drawing from pool 2 creates positive synergies that feedback to sustainability for nature and humans that depend on it (p.63-66).

The intersection of justice, love for neighbor, and western Christianity’s culpability in blessing cultural movements of colonialism, wealth accumulation, consumption, and separation of humanity from the rest of creation puts the issue of climate warming squarely in the laps of modern Christianity. Instead of giving up chocolate as a Lenten discipline to focus your contemplation, I suggest reading and contemplating the AR6.

Tim Van Deelen

Tim Van Deelen is Professor of Forest and Wildlife Ecology at the University of Wisconsin – Madison. He grew up in Hudsonville, Michigan, and graduated from Calvin College. From there he went on to the University of Montana and Michigan State University. He now studies large mammal population dynamics, sails on Lake Mendota, enjoys a good plate of whitefish, and gains hope for the future from terrific graduate students. 


  • Daniel Meeter says:

    Our Jeremiah prophesying in the court of the Lord’s House, warning against the destruction that will follow unless God’s people change our ways. I bless you and thank you.

  • Mark Kornelis says:

    Many thanks for continually sounding the alarm on this most important topic, and for doing so with such clarity and passion. I will, as you encourage, read and contemplate the AR6. In thinking of what an appropriately scaled response would look like, are there recommended sources or tools to help readers move to the next step, or better yet jump multiple steps ahead in their personal response? I’ve referenced and recommended Project Drawdown in the past ( Are there better sources to help us move from contemplation to action?

    • Tim Van Deelen says:

      Thanks Mark. Project Drawdown is good. Off the cuff, I’d say pay attention to the work of Bill McKibben (writer, Christian) for news and activism. Pay attention to Katherine Heyhoe (climate scientist, Christian, expert science communicator) for news and translatable science discussion. Pay attention to The Guardian (news outlet that doesn’t take fossil fuel advertising) for news and opinion.

      For energy and thoughtfulness, Debra Rienstra’s book (Refugia Faith…) is essential. Also Kathleen Dean Moore’s “Great Tide Rising.” KDM is a retired philosophy prof who finds and writes about the energy she finds in imaging her grandchildren’s future. Both of these books are written beautifully.

    • Terry Woodnorth says:

      If you want to move to action, I recommend reading the following books for inspiration and ideas:
      – Saving Us: A Climate Scientist’s Case for Hope and Healing in a Divided World by Katharine Hayhoe
      – Following Jesus in a Warming World: A Christian Call to Climate Action by Kyle Meyaard-Schaap
      Also, joining Citizens’ Climate Lobby will help you to take meaningful and regular actions.

  • Joyce and Wes Kiel says:

    Thank you for keeping this issue on our radar Tim. You added another twist (for me) in regard to how climate change will affect the low income and impoverished people in our world. We sent this to my college aged granddaughters as a conversation starter for Easter to hear hopefully how their generation relates to it. Joyce and Wes

  • Jim Day says:

    Thanks very much again Tim. So much to do, so little time. We can continue to do the little things individually, but how to get those with policy making power to actually do what needs to be done is the forever struggle. Rome is burning, again. And it is (the) US this time. Lord help us to help those to help everyone. Peace.

  • Don Tamminga says:

    Thanks. Feels so hopeless sometimes.

  • Tim Van Deelen says:

    Clarification: I read the Synthesis Report for the Sixth Assessment Report (title, released 3/20). That’s different than the Working Group I Assessment Report (AR6)1 on the physical science basis of climate change that Debra Rienstra blogged about on August 14 2021. The recent report is a synthesis of assessment reports from Working Group 1 – 3. I used the acronym “AR6” above but should have used “SYR6” to make the distinction between the synthesis and the other assessments.

  • John Paarlberg says:

    More than 20 years ago The RCA Commission on Christian Action was sounding the alarm: “Global climate change is an issue of justice. The industrialized nations, representing less than 20 percent of the world’s population, are responsible for 75 to 80 percent of the annual greenhouse gas emissions. Yet those who live in poor and developing nations are the ones who will be most seriously affected by global warming. The North American suburbanite can afford to turn up the air conditioner and pay a little more for groceries. The peasant living in coastal Bangladesh would become an environmental refugee. Climate change is also an issue of intergenerational justice. The effects of global warming in our lifetimes may be minimal. It will not be so for our children and our children’s children. Current North American energy-rich and overly consumptive lifestyles are being subsidized by the poor and by future generations” (Report to the RCA General Synod, 1999). Yet this was far too mild. The effects of global warming in our lifetimes are not minimal. Human caused climate change is here and people are suffering and dying because of it. The matter is urgent. What we do–or fail to do in the next few years will have life or death consequences for millions, perhaps billions of people.

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