· 8 min read
On the eve of US Climate Week in NYC, I thought I would write a US-focused summary of the state of the US discussion. The U.S. Department of Energy’s July 2025 climate report, A Critical Review of the Impacts of Greenhouse Gas Emissions on the U.S. Climate (the “Report”), acknowledges that if the Earth’s climate sensitivity (ECS) exceeds 4.5°C, “immediate aggressive” emissions reductions are required (see page 25, Section 4.1). The past decade (2015–2024) has been the warmest in recorded history and the warmest in the past 125,000 years, with current warming rates of approximately 0.4°C per decade or more — double the DOE’s 0.2°C value. This trend indicates that climate sensitivity has already crossed the DOE’s threshold for urgent action. While the “traditionally” assumed an ECS of 3.0°C, the observations of the past ten years clearly indicate an ECS much higher and at or over the limit the Report calls for “immediate aggressive” action.
This Report received tens of thousands of public comments including from Dessler and Koop who put together comments from over 80 scientists (the “Experts”) over 450 pages that well represent the current state of our understanding of the climate.
The work on this Climate Working Group (“CWG”) Report was terminated by Secretary Wright due to legal challenges and the overwhelming public response. Responding to many of these comments would have been time-consuming and I claim problematic. Nevertheless, the Report provides a useful process to examine the state of the climate change discussion.
I observe to the Experts, the UN-sponsored International Panel on Climate Change (“IPCC”) process is entirely academic and has not created political consensus in the US. There is legitimate push back, and name-calling and debating have not worked; rather, they have made forging consensus more difficult. I talk to many climate skeptics who are smart, well educated, well intentioned, informed, and they are in fact not convinced.
And for the Unsettled members of the CWG, I would challenge them to develop a position that is consistent with current observations and all the data, and to quantify their uncertainty issues relative to the actual overall data. I claim any professional analysis that includes all the data will come to the conclusion already found in the Report: “immediate aggressive” action is now required.
The third actor in this story is Earth; the Earth is speaking with increasing volume and clarity that cannot be ignored. The Earth is not reading the various IPCC reports, or the CWG’s positions, but Earth is providing very clear and alarming data that must drive the Report’s final document.
Forty years into the modern climate change discussion, the real story has nothing to do with climate models and various uncertainties rather actual climate data. Forty years ago, people needed to input guesses to models that were themselves guesses; forty years later, we have actual data, and these observations are telling an unavoidable story.
Sifting through hundreds of issues and comments, I will address the most significant, which in the DOE Report is buried deep on page 25. The DOE Report claims that “if ECS is very high (above 4.5°C) “, immediate aggressive emission controls become more imperative…” (DOE Report Section 4.1).
The last ten years were the Earth’s warmest years in 125,000 years: Earth is speaking clearly: we have breached this 4.5°C climate sensitivity (the ECS) metric and, therefore, as the DOE Report itself finds, “immediate aggressive” action is now “imperative”. The ECS, meaning equilibrium climate sensitivity, which is an odd construct representing the amount of global temperature response to a doubling of CO2 from a pre-industrial reference, and this metric should be abandoned as a relic of history – it’s not measurable, and there are other metrics that are currently observed.
The current condition of Earth is halfway to the doubling of the pre-industrial level CO2, and the Earth has already experienced an approximately 1.5°C temperature rise, which was the goal of many to avoid. The “traditional value” for this ECS is 3.0°C; things being linear, the long-term average 3.0°C ECS seems reasonable – that’s just more of the same, assuming the traditional temperature growth is 0.2°C rise per decade. But the rate of change has clearly increased, and the linear condition is not observed and representing a fatal flaw.
The climate sensitivity/ECS is addressed in the Expert’s Response and is equally buried on page 95, “Internal Incoherence: The report is undermined by critical logical inconsistencies. It champions a climate sensitivity estimate that, by its own stated policy threshold, justifies the very emissions controls it argues against …”
Earth has spoken and clearly spoken – she is now warming at an alarming and exponential rate, at or greater than 4.5°C ECS. None of the references cited by the DOE Report’s Section 4 include the last five years of climate data – the five warmest years in human history, many references cited don’t include any of the last ten years of data – the ten warmest years.1 Imagine a stock analyst discussing the price of Tesla stock by analyzing the 2015 price at $14.62 without discussing that the current price is over $400. That is exactly what the CWG is doing.
The Earth is experiencing exponential warming, meaning that the Earth is warming and the rate of warming is increasing. The Earth was warming at 0.2°C/decade and now it is warming at more than 0.4°C and this rate is increasing. The probability that the global temperature in 2024 will occur is less than 1/1000. A new and warmer normal Earth has been established, and warming is occurring at an increasing and exponential growth rate. Therefore, ignoring the last five or ten years of data is a fatal flaw. The joint probability that these ten years in a row would occur is 1 in 10^21 (a 10 with 21 zeros behind it), or almost surely zero, as they say in the math department.
Earth is today clearly experiencing 0.4°C per decade growth, well over the high end of the projections discussed in the DOE Report, and this 0.4°C growth is accelerating and is most likely higher (as of 2024 the rate for the prior five years was 0.6°C per decade for example) and is indicative of an ECS climate sensitivity that exceeds the high end of the DOE Report’s 4.5°C high estimate.2,3 ECS is a relic to climate modeling, which is thankfully no longer relevant as the Earth’s climate has already changed, and we have observed the outcome. We must use all the climate data, and all climate conversations must include the current observed condition. To preempt a rebuttal, to claim that our observed 0.4oC+ per decade growth rate is not at or exceeding a CO2 sensitivity/ECS over 4.5 is not plausible or consistent with the CWG’s written record.
With global temperatures now rising at least twice the expected rate, the DOE’s own findings make clear that “immediate and aggressive” climate action is no longer optional but “imperative.”
This acceleration in warming well past the DOE reference rate of 0.2°C/decade is supported by multiple scientific analyses. My own amateur analysis of NASA’s global temperature data indicates that the Earth is warming at a rate far beyond the scenarios considered moderate in the DOE report. Adjusted datasets that account for natural variability factors—such as El Niño, volcanic activity, and solar cycles — confirm a significant increase in the rate of warming (Foster 2025). And the State of the Climate 2024 papers published in the Bulletin of the American Meteorological Society in August 2025 likewise confirm an increasing rate of climate change.
From the NASA GLB Data Set accessed August 2025, the last ten years are a Knock Out Punch to climate skepticism. A note on the data, there are several datasets, and they all produce the same outcome: an exponentially growing rate of global temperature change; there is no uncertainty that takes the 95% confidence range out of exponential growth.
Adjusting the second and third order variables for urban heat effect, missing data here and there, a bit more solar uncertainty – does not change the finding of exponential growth. The NASA data clearly exhibits exponential growth within a 95% confidence interval.
Figure 1: NASA GLB dataset with probability of occurrence calculated in Excel and charted with MATLAB exponential curve fit with 95% confidence intervals displayed
Foster 2025 reports: “removing the best estimate of the influence of three natural variability factors on global temperature reduces the noise level of the data sufficiently to reveal a large and significant acceleration of global warming. The most important insight from these adjusted data is that there is no longer any doubt regarding a recent increase in the warming rate.”5 Foster 2025 also concludes that Earth is now warming at 0.4°C, twice as high as the 0.2°C/decade rate previously observed. Foster 2025 corrects for the three largest natural variability factors: El Niño, volcanism, and solar variation.
The State of the Climate 2024 was published in the August 2025 Bulletin of the American Meteorological Society.6 It reports that for the second year in a row, record-high global surface temperatures were set in 2024. The last 10 years (2015–24) are now the warmest 10 in the instrumental record — warmer than the 2011–20 average — and hence “more likely than not warmer than any multi-century period after the last interglacial period, roughly 125,000 years ago”.
Hawkins 2025 also confirms the accelerating rate of global temperature and also puts it into longer-term perspective.7
Earth has spoken and the state of the climate is the warmest in human existence. The omission of recent data by both the DOE report undermines the relevance to today’s policy decisions. Earth’s present state—marked by record-breaking warmth and accelerating trends.
Any climate analysis used for policy making must bridge to the existing boundary condition, which is Earth’s current condition, and that leads us to the inevitable outcome of “immediate aggressive” action as clearly described in the DOE Report. Likewise, the economic costs of mitigation measures must also tie to current observations, but that discussion is for another day.
Through the simple process of bridging to our current condition of the State of Earth, America can forge consensus across ideological divides on these important issues.
lluminem Voices is a democratic space presenting the thoughts and opinions of leading Sustainability & Energy writers, their opinions do not necessarily represent those of illuminem.
Track the real‑world impact behind the sustainability headlines. illuminem's Data Hub™ offers transparent performance data and climate targets of companies driving the transition.
