For years, the CO2 Coalition and independent scientists have warned that the U.S Fifth National Climate Assessment (NCA5) rested on a foundation of sand. [some emphasis, links added]
Its dramatic projections of catastrophe relied heavily on U.N.-sponsored Representative Concentration Pathway 8.5 (RCP8.5) and its successor SSP5-8.5, both extreme predictions of carbon dioxide (CO2) emissions that were treated as realistic.
As far back as 2017, scientists noted the far-fetched nature of the U.N. predictions. In August 2026, the Trump administration proposed an amendment to NCA5 that acknowledges its emission forecasts are implausible and must not guide federal policymaking.
This is a welcome restoration of scientific integrity.
The amendment, issued under the U.S. Global Change Research Program (USGCRP) and aligned with Executive Order 14303, “Restoring Gold Standard Science,” states that results dependent on RCP8.5, SSP5-8.5, or equivalent emission scenarios “should not be used as expected, baseline, business-as-usual, likely, central, or policy-relevant federal planning futures.”
Any NCA5 figure, table, or claim based on these “implausible” scenarios must carry an explicit caveat. Projections of damages, health effects, or ecosystem collapse cannot stand alone as policy premises without comparison to plausible alternatives and real-world observations.
This correction is long overdue.
RCP8.5 was never designed to forecast the most likely future. It was constructed as an upper bound for climate-model experiments—an exploratory tool of imaginary, extreme conditions.
Its predictions of global warming defied observed trends in coal consumption growth, technological development, and socioeconomic trajectories, according to multiple peer-reviewed analyses.
Treating extreme emission scenarios as ordinary distorted the entire National Climate Assessment. It inflated projected impacts, fueled exaggerated risk narratives, and justified costly regulatory interventions that ignored economics and human welfare.
The amendment properly requires that such results be contextualized or set aside for decision-making.
Yet this amendment, while necessary, is only a first step. NCA5’s deeper problems remain.
It continues to lean on climate models that have systematically overestimated warming and failed basic observational tests. It elevates politically driven documents of the U.N.’s Intergovernmental Panel on Climate Change over scientific data.
Most critically, it omits the extraordinary benefits of rising atmospheric CO2 and of the fossil fuels that produce it.
CO2 is not a pollutant; it is the essential plant food that makes life on Earth possible. Current concentrations, near 420 parts per million, remain far below levels that have prevailed for much of Earth’s history and are still low for optimal plant growth.
Decades of laboratory and field evidence demonstrate that elevated CO2 increases photosynthetic rates, improves water-use efficiency, and boosts crop yields—wheat by 20% to 30% and soybeans by up to 46% under controlled conditions.
Satellite observations confirm global greening, with rising CO2 responsible for most of the increase in leaf area across vast regions. Nitrogen fertilizers derived from fossil fuels support roughly half the world’s population.
Without affordable energy and the CO2 fertilization effect, feeding eight billion people becomes far more difficult.
Modest warming itself brings many benefits, including longer growing seasons in temperate zones, reduced cold-related mortality (which exceeds deaths from heat), and expanded habitable ranges.
Trends of weather-driven disasters—hurricanes, tornadoes, wildfires—do not match the alarmist storyline when examined against long-term records rather than model outputs.
The real catastrophe would come from policies that deliberately restrict reliable energy in pursuit of net zero. Such policies raise energy costs, harm the poor, slow development in the Global South, and risk food insecurity by limiting fertilizers and mechanization.
True gold-standard science demands that we begin with observations, test models against data, disclose assumptions transparently, and weigh risks and benefits.
Future assessments must evaluate every emission scenario on empirical grounding, not institutional pedigree. They must acknowledge that humanity’s use of fossil fuels has lifted billions from poverty while restoring CO2 to levels that enhance the biosphere.
Validating what rigorous scientists have documented for years, the proposed NCA5 amendment is progress.
Now, policymakers should seize this moment to reassess the entire report against observations, restore balance by including the benefits of CO2, and reject fearmongering that has driven policy for too long.
Energy abundance, a greener planet, and prosperity can be celebrated and advanced further through the application of science when ideology is set aside.
Read more at CO2 Coalition
