By Joshua Arnold

A U.N. committee tasked with modeling climate change has now discarded its most alarmist models, admitting after years of criticism that they “have become implausible.” Announced with little fanfare in early April, the change became widely known after President Donald Trump celebrated the reversal of “Climate Alarmism nonsense” on Saturday. The scientific admission gives his administration an opening to push for systemic reforms.

The change in models represents a shift between the Intergovernmental Panel on Climate Change’s (IPCC) Sixth Assessment Report (AR6), finalized in 2023, and its seventh (AR7, date forthcoming). Under AR7, the scenario with the greatest warming will show approximately 25% less warming by 2100 than the “worst-case” model in AR6.

Trump’s Reaction

“GOOD RIDDANCE!” Trump proclaimed over the demise of the previous alarmist model. “The United Nations TOP Climate Committee just admitted that its own projections (RCP8.5) were WRONG! WRONG! WRONG!”

As he so often does, President Trump showed solid political instincts but a tenuous grasp of the details. Thus, he grasped the political implications of the change at once, “For far too long Climate Activism has been used by Dumocrats to scare Americans, push horrible Energy Polices, and fund BILLIONS into their bogus research programs. Unlike the Dumocrats, who use Climate Alarmism nonsense to push their GREEN NEW SCAM, my Administration will always be based on TRUTH, SCIENCE, and FACT!”

Trump can justly declare victory over the U.N. climate bureaucrats because he had specifically targeted the RCP 8.5 scenario in a May 23, 2025 executive order on “Restoring Gold Standard Science.” Trump wrote, “RCP 8.5 is a worst-case scenario based on highly unlikely assumptions like end-of-century coal use exceeding estimates of recoverable coal reserves. Scientists have warned that presenting RCP 8.5 as a likely outcome is misleading.”

However, it is also “misleading” to claim that the U.N. Climate Committee simply admitted that its previous work was wrong. Not that the highly technical explanation would interest President Trump; before all the terms were even introduced, he would likely dismiss the whole issue. “Boring! I have no time for climate change beyond refurbishing D.C.‘s golf courses.”

Going Deeper

Perhaps you have the same revulsion to thinking overly hard about all that “science-y stuff.” This professional creative takes no offense if you choose to skim over the more technical paragraphs that follow. After all, I myself did not wake up this morning with a burning desire to know the significance of “Watts per meters squared” (W/m²).

However, if we want to penetrate the ancient temple of the so-called experts and take back from them our rightful duty to exercise common sense and ordinary reasoning without suppression, we must first hack our way through the overgrown jungle of their stagnant verbiage.

The Old Model

The first task is to understand the targeted, and now discarded, RCP 8.5. The IPCC’s Sixth Assessment report chose to model at least four “Representative Concentration Pathways” (RCPs), which is an obtuse way to say that they plotted out future scenarios (based on assumptions about demographics, technology, economic growth, and climate change policies) to the year 2100.

The most alarmist scenario, RCP 8.5, predicted that atmospheric greenhouse gases would reach a CO₂ equivalent concentration of 1,313 parts per million (ppm) and raise global temperatures by 3.7 degrees Celsius, compared to the global average temperature in the two decades from 1986-2005.

The four RCP scenarios were distinguished by numbers: 2.6, 4.5, 6.0, or 8.5. These numbers are the hypothesized values for each scenario corresponding to the units W/m², a measure of energy absorption (incoming energy minus outgoing energy) that is used for solar panels. For some reason, this measurement is called radiative forcing (RF), a name which suggests to the untrained ear something negative.

It gets more complicated, however. Climate scientists define these measurements of RF relative to the earth’s energy absorption in 1750 AD, which they define as zero. This selection date already defines “normal” temperatures as too high. 1750 happens to fall in the midst of a period known as the “Little Ice Age,” which saw growing glaciers and a decline in Northern Hemisphere temperature of approximately 0.6 degrees Celsius, according to Encyclopedia Britannica. Yet, since the Industrial Revolution began shortly afterward in England, it is taken as the benchmark for all warming comparisons.

However, even defining energy absorption as zero in 1750 entails a massive assumption, since no one was taking measurements that would verify this assumption. Indeed, the very concepts of energy and power were not yet formalized, and the Watt as a unit of measurement was not formalized until the1948 General Conference on Weights and Measures. In 1750, even James Watt himself, after whom the unit was named, was only 14 years old, and he would not invent his steam engine until 1776 (yes, that 1776) — it was a big year.

For perspective, climate models showed an RF measurement of 2.29 W/m² in 2011. Thus, the RCP 2.6 scenario showed very little increase in atmospheric greenhouse gas concentration, while RCP 4.5 and RCP 6.0 showed gradually more. The RCP 8.5 scenario assumed that, although global energy absorption increased an estimated 2.29 W/m² in the 261 years after 1750, it would nearly quadruple that measurement in the next 89 years, to reach 8.5 W/m² by 2100.

Was this a plausible scenario? Some scientists never thought so, and a growing chorus of critics derided the model even before the IPCC finalized its AR6. Part of the problem stems from the criteria used to develop the models. “The RCPs should be based on scenarios published in the existing literature, developed independently by different modeling groups and, as a set, be 'representative’ of the total literature,” a 2011 article detailed. “At the same time, each of the RCPs should provide a plausible and internally consistent description of the future.”

Pielke argues at length that higher models never boasted much internal consistency and utterly lacked plausibility. For instance, they postulated exaggerated estimates of world population in 2100 (such as 13 billion) that far exceed current growth rates. However, the inflated population yields inflated estimates of greenhouse gas emissions.

Through some iterations of the research, the RCP 8.5 was also dubbed the SSP5-8.5, when the models came to be defined as “Shared Socio-economic Pathways.” In this iteration, RCP 6.0 was replaced by SSP3-7.0 as the second-most alarmist scenario. The SSP3-7.0 model predicted a rise in global temperatures approximately 0.7 degrees Celsius less than SSP5-8.5. These terms will be relevant soon.

The New Model

As U.N. scientists began to prepare AR7, they chose to discard the old model of RCP scenarios and adopt a new model system, with labels ranging simply from “High” to “Very Low.” The stated reason for this change is that “high emission levels (quantified by SSP5-8.5) have become implausible, based on trends in the costs of renewables, the emergence of climate policy, and recent emission trends.”

The change comes from the Scenario Model Intercomparison Project (ScenarioMIP), a committee within the Coupled Model Intercomparison Project (CMIP), which is itself an organ of the World Climate Research Programme (WCRP). The project is also “co-sponsored by the World Meteorological Organization, the International Science Council, and UNESCO’s Intergovernmental Oceanographic Commission,” writes American Enterprise Institute senior fellow Dr. Roger Pielke, Jr.

(Perhaps that’s part of the problem right there. If the international climate change bureaucracy were smaller, perhaps it would produce less hot air.)

Pielke ran both the old and new scenarios “through the same emulator with identical parameters to ensure that the results are apples-to-apples.” He found that the “High” scenario under the new system resulted in a prediction of 45% less cumulative emissions by 2100 than the SSP5-8.5 model and 9% lower than the SSP3-7.0.

In other words, the new highest model for global warming under consideration by U.N. climate scientists shows less greenhouse gas accumulation and less warming than the top two models under consideration just three years ago.

Pielke argued that the new “High” scenario was still implausibly inflated. It still relied on exaggerated expectations of world population growth and predicted energy absorption (RF) “well above” the “upper end” of more than 1,000 other scenarios he tested in 2022. As he points out, even the committee members admit, “this scenario is not a ‘business-as-usual’ scenario nor the no-policy reference scenario for the other scenarios. The scenario is intended to explore the upper end of GHG emissions resulting from deep political, technological, and structural deviation from current trends.”

“The HIGH scenario is not a projective scenario, but a ‘what if?’ exercise,” he concluded.

Pielke argued that the “Medium” scenario was also inflated to the point that “The new MEDIUM might be considered a worst-case scenario rather than a current policy scenario.” In other words, the newly updated U.N. climate models do not abandon alarmism, they simply trim back the worst excesses of it.

Implications

It is hardly news that U.N. climate bodies vastly over-estimate the effects of climate change. On occasion, they even issue shockingly inaccurate predictions that must later be retracted. For instance, a 2007 report suggested that the Himalayan glaciers could melt away by 2035 — a claim the IPCC had to withdraw by 2010.

Thus, it is no great feat for U.N. scientists to replace their most alarmist prediction with a less alarmist prediction.

However, the change is nevertheless significant because of the global influence of the U.N. report. According to GB News, the RCP 8.5 scenario had been cited more than 45,000 times in academic papers. The Network for Greening the Financial System framework, used by more than 140 central banks, including the U.S. Federal Reserve, has used the RCP 8.5 to calibrate physical risk. Even U.S. government agencies cited U.N. models as the basis for their climate predictions.

In other words, a whole system — academic, economic, governmental — has been built on the RCP 8.5, based on a belief in man-made climate change. This system usually results in policy decisions that are anti-human, restricting energy production, economic growth, and even marital procreation. Now that the U.N. scientists have revised their most alarmist model downward by 25-45%, the whole system built on its recommendations should have to revise their own extrapolations of the data, for a proportional lessening of its policy effects.

A significant reason why the U.N. models are so important is the gargantuan size — in computer data — of a worldwide, century-long climate model. “Most climate researchers don’t work directly with global climate models, as they are so enormous they can only run on government-funded supercomputers,” explained Progressive Reform last month. “And each model run takes a significant amount of energy and time to produce.” The U.N. scientists’ work meets with very little criticism because few researchers have access to the resources to even check their work.

Notably, the organization added, with so much time, money, and opportunity cost on the line, “RCP 8.5 has historically been the scenario run for every climate model which the IPCC uses.” Not anymore.

As the name suggests, “Progressive Reform” is a left-leaning policy organization that tried to legitimize the ongoing use of RCP 8.5. “RCP 8.5 remains not only legitimate, but crucial,” they pleaded. “Why are scientists still using RCP 8.5 in their research? They are not out to shock or deceive; they are simply following the best science. That RCP 8.5 has become unfairly understood to be a ‘controversial’ choice of scenario is a distortion of climate science.”

But their last-ditch effort was doomed to fail. Only days later, the U.N. committee published its complete overhaul of the climate models, which substantially walked back the worst-case scenario. To the extent that politics interacted with this decision, this was a win for the Trump administration, which had openly opposed RCP 8.5, and a loss for the progressive think tanks still trying to pretend that this alarmist hypothetical was plausibly related to reality.

“We’ve known since 2017 that upper-end climate scenarios are fatally flawed. Nine years later, that understanding has now become officially recognized,” Pielke summarized. “That is good news.”

Joshua Arnold is a senior writer at The Washington Stand.

This article originally appeared here.