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Alan Northcutt: Analyzing IPCC Assessment Report 6

Alan Northcutt: Analyzing IPCC Assessment Report 6

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During the summer of 2021, the scientifically predicted impacts of global warming were on full display: deadly heat waves in the U.S. West, Canada and Europe; megadrought in the West; extreme rainfall with flooding in the U.S. East and Asia; and massive wildfires in the West, Mediterranean and Siberia. And then, as if to add to the climate onslaught, a much anticipated and extremely troubling new report was released by the Intergovernmental Panel on Climate Change (IPCC) on Aug. 9 — Part 1 of Assessment Report 6, or AR6.

Authoritative AR6. This document is the gold standard of climate science because it received three layers of approval. First, 14,000 climate research papers were peer-reviewed and published in the scientific literature. Second, 230 IPCC scientists distilled from these a 4,000-page summary communique. And third, the wording of the volume was fine-tuned and endorsed by 195 member nations of the Paris Agreement. AR6 provides the state of knowledge of climate science, based on new data sets and more powerful computer modeling than AR5, published eight years ago. A few highlights of this mammoth document will follow.

Climate change certainty. At the heart of AR6 is the following: “It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred.” In other words, the scientific certainty that climate change is happening and is manmade has now increased to a level that removes any doubt. Further, the impacts are “unprecedented,” and every increment of warming worsens heat waves, droughts, wildfires, extreme rainfall and flooding, ice sheet collapse, permafrost melting, sea level rise, superstorms, ocean heat waves and acidification, ocean current weakening, and deforestation.

Projections update. AR6 reports that the global mean temperature is now 1.1 C rather than 1.0 C above the pre-industrial mean. And with all foreseeable emission scenarios, the world will reach 1.5 C above the preindustrial mean by 2040. That means a heat wave that occurred once every 50 years before the industrial revolution will occur every 6 years after 2040. And if emissions are not cut sharply, in 2100 the global mean temperature could rise to 4.4 C or 5.7 C above preindustrial — a truly devastating outcome.

Attribution science. In the past, it was always asserted that individual weather events could not be definitely attributed to climate change. That belief has changed. A major advance since the last assessment report is the knowledge that science can determine that climate change caused a specific event. For example, attribution studies, running thousands of computer climate simulations, with and without climate change effects, have found that the recent heat wave of the Pacific Northwest was “virtually impossible” without the effects of climate change.

Waco findings. AR6 contains fact sheets for the various geographic regions of the globe. For Central North America (CNA), the region in which Waco resides, increases in drought and fire weather have been observed, and the increase will continue into the future. There are also projected increases in extreme precipitation, river flooding and rainfall (pluvial) flooding. We then focus specifically on Waco, utilizing the detailed AR6 interactive atlas and Waco’s longitude and latitude coordinates. If the world continues business-as-usual (no greenhouse gas emission reductions), the following are projected in Waco by 2040: intense warming with maximum annual temperature of 111 F (43.9 C) and 23 days annually over 104 F (40 C). By 2040, the atlas computes there will be 26 consecutive dry days (precipitation less than 1 mm) and a maximum 1-day precipitation of 2.49 inches (63.3 mm). This rainfall data highlights the fact that anthropogenic climate change often produces extremes at both ends of the rainfall scale.

The response. The ongoing weather/climate disasters and the AR6 report are clearly disheartening. But this new IPCC report also emphasizes that there is still time to avoid the worst impacts of the climate crisis — through mitigation at all levels. Certainly, international and national initiatives are vital, but Waco area contributions are also critical. Local mitigation includes:

  • Individuals: Use 100% renewable electricity, install solar, maximize home efficiency, drive electric vehicles (EVs), eat less meat.
  • Businesses: Install solar, use electric fleet, provide EV charging.
  • City/county: Use 100% renewable electricity, install solar, use electric fleet, provide incentives for citizen solar and EV purchase.
  • School districts: use 100% renewable electricity, install solar, use electric school buses, provide EV charging for students and staff.

As U.N. Secretary-General António Guterres remarked: “The Assessment Report 6 is code red for humanity. … If we combine forces now, we can avert climate catastrophe. But, as today’s report makes clear, there is no time for delay and no room for excuses.”

Alan D. Northcutt is a retired Waco physician and director of a grassroots climate action and education group, Waco Friends of the Climate.

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